Scientific Program

The Klein-Gordon equation on curved space-times: an application of deformation quantization

ABSTRACTS

Title: Renormalized Kaluza-Klein Theories

Abstract:

The expansion of the renormalized theory in harmonics of the extra dimensional compact manifold is compared with the renormalization of the harmonic expansion of the lagrangian.

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Antoniadis, Ignatios (CERN, Switzerland)

Title: Extra dimensions and possible modifications of Newton's law

Abstract:

Not provided

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Arteaga, Daniel (UB, Barcelona)

Title: Particle propagation in cosmological backgrounds

Abstract:

We will analyse the quantum propagation of interacting particles in an expanding universe. By studying a particular, yet physically meaningful, field theory model, we will show that the dispersion relation of the particles (i.e., the energy as a function of the momentum) is modified because of the cosmological background. We will also show that even stable particles develop an effective decay rate in an expanding universe. Applications to the trans-Planckian question will be briefly discussed.

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Asorey, Manuel (Uniz. Zaragoza)

Title:Vacuum energy and Renormalization on the Edge

Abstract:

The dependence of vacuum energy on boundary conditions reveals the existence of new singularities which either involve space topology change or edge states with unbounded below classical energy. The effect can be understood in terms of a topological index on the space of boundary conditions. There is an interesting connection between the vacuum energy on the bulk and global aspects of the renormalization group flow on the boundary. The analysis of this renormalization group flow reveals peculiar behaviours including ciclyc orbits and conformal invariant fixed points.

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Babichev, Eugeny (MPI Munich, Germany)

Title: Looking beyond the horizon

Abstract:

We show that if there exists a special kind of Born-Infeld type scalar field, then one can send information from inside a black hole. This information is encoded in perturbations of the field propagating in non-trivial scalar field backgrounds, which serves as a "new ether". Although the theory is Lorentz-invariant it allows, nevertheless, the superluminal propagation of perturbations with respect to the "new ether". We found the stationary solution for background, which describes the accretion of the scalar field onto a black hole. Examining the propagation of small perturbations around this solution we show the signals emitted inside the horizon can reach an observer located outside the black hole. We discuss possible physical consequences of this result.

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Bastero-Gil, Mar (U Granada)

Title: Supersymmetric Hybrid Inflation with Minimal and Non-Minimal Kahler potential

Abstract:

Minimal supersymmetric hybrid inflation based on a minimal Kahler potential predicts a spectral index n_s >= 0.98. On the other hand, WMAP three year data prefers a central value n_S ~ 0.95. We propose a class of supersymmetric hybrid inflation models based on the same minimal superpotential but with a non-minimal Kahler potential. Including radiative corrections using the one-loop effective potential, we show that the prediction for the spectral index is sensitive to the sall non-minimal corrections, and can lead to a significantly red-tilted spectrum, in agreement with WMAP.

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Title: Gravity and Quantum Fields in Discrete Space-Times

Abstract:

We investigate the properties of gravitons and quantum fields in a six dimensional space-time where both extra dimensions are discrete. The effective four dimensional theories depend on the discretization, which yields different mass spectra for the fields. Some applications will be discussed, e.g., generating small fermion masses.

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Title:An inflationary scenario mitigating the cosmological constant problem

Abstract:

Among other things, the difficulty in solving the cosmological constant (CC) problem consists in the fact there is no known dynamical mechanism to determine it. It is rather seldom acknowledged that there are two different aspects of CC 1) as a purely geometric term in Einstein equations.2) as the ground state of a scalar field(no kinetic energy) At finite temperature, in a second order phase transition, the above two are not the same because 1) is a genuine constant while for 2) the mass term of the Higgs field driving the phase transition depends on temperature Taking into account the above considerations and the explicit form of the temperature dependent mass tem we arrive at a set of quite involved equations; a mix of analytical and numerical methods reveals two features: i) near a second order phase transition there is an inflatioary period but accompanied by a small decrease in temperature ii) because in the broken phase the contribution of the Higgs potential energy is negative , the two CC, geometrical and Higgs, almost, but not exactly, compensate.

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Title:Cosmology from decaying dark energy, primordial at the Planck scale

Abstract:

The consideration of dark energy's quanta, required also by thermodynamics, introduces its chemical potential into the cosmological equations. Isolating its main contribution, we obtain solutions with dark energy decaying to matter or radiation. When dominant, their energy densities tend asymptotically to a constant ratio, explaining today's dark energy-dark matter coincidence, and in agreement with supernova redshift data, and a universe-age constraint. This also connects the Planck's and today's scales through time. This decay may be manifested in the highest-energy cosmic rays, recently detected.  

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Title: Status of neutrino masses and mixings and future perspectives

Abstract:

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Title: Chaplygin-gas cosmology: unification of dark matter and dark energy

Abstract:

In order to explain the current accelerated Hubble expansion,aside from the cosmological constant, a variety ofmodels based on `quintessence' and `k-essence' have been put forward.One characteristic of the aforementioned models is theassumption that dark energy is separate and distinct from dark matter. A rather different idea, which has been dubbed 'quartessence', is that both dark energy and dark matter are aspects of a unified theory. The first definite quartessence model was based upon the Chaplygin gas,a fluid obeying an exotic equation of state in which the pressure is a negative inverse of the density, p = - A/rho. This equation of stateis obtained in the Dirac-Born-Infeld theory for a 3+1 dimensional D-branein a 4+1 bulk. Solving the field equation in a FRW universe shows that the model interpolates between dust at small scale factor a and a cosmological constant at large a.

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Title: A new gauge symmetry for Eintein's equations

Abstract:

In this talk we will show how from arguments of the QFT of a massless spin-two particle we arrive at a whole bunch of possible gauge symmetries for the non-linear completion, all of them sharing the Area Preserving Diffeomorphisms (APD) at linear level. Two possibilities (the whole diff and APD plus a Weyl symmetry) have the Einstein's equations as e.o.m., with a difference in the way in which the cosmological constant appears. We will also comment on the anomalies and renormalizability of this kind of gauge theories.

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Brevik, Iver (Norwegian U. of Science and Technology, Norway)

Title: Dark energy and viscous cosmology

Abstract:

It is shown how the physically natural assumption of letting the bulk viscosity be proportional to the scalar expansion in a spatially flat FRW universe can drive the fluid into the phantom region (w < -1), even if it lies in the quintessence region (w > -1) in the non-viscous case. Similar behaviour is found in the case of modified gravity.

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Title: A nonequilibrium renormalization group approach to turbulent reheating

Abstract:

Numerical simulations of reheating after inflation show that the initial phase of preheating, where a narrow range of field modes are amplified by the oscillations of the inflaton field, is typically followed by a stage of "turbulent" reheating, where energy is redistributed across the spectrum in the form of energy cascades both towards the ultraviolet and the infrared. During turbulent reheating, the spectrum as a function of wave number is well described by a power law with a time dependent exponent, approaching an equilibrium Rayleigh - Jeans spectrum at late times. Similar phenomena are believed to occur in the early stages of relativistic heavy ion collisions.To analyze the turbulent reheating stage, we propose to generalize the Kadanoff - Wilson renormalization group (rg) approach to field theories to a nonequilibrium setting. The generalization consists in that the rg is formulated as a map in the space of Schwinger - Keldysh effective actions, rather than the action of the underlying field theory, and a new parameter T is included, which represents the characteristic time scale over which the system is being observed. The nonequilibrium rg reduces to the equilibrium one when T is taken to infinity, but has a much richer structure at finite T. In particular, the anomalous dimension of the field is T-dependent, and this may be exploited to give a theoretical interpretation of the evolution of the turbulent reheating spectrum.

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Title: A dynamical system approach to higher order gravity

Abstract:

Recently the idea to model dark energy with higher order corrections to General Relativity has became more and more popular. In this talk I will give a detailed analysis of the properties of the cosmology of a specific higher order theory of gravity (R^n gravity) using the dynamical system approach (see gr-qc/0410046 and gr-qc/0603012 ). This powerful method allows to derive the global features of this model and to obtain new exact solutions in both Friedmann and Bianchi I universes. The possible further development of this approach are discussed.

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Carneiro Saulo (U. Federal da Bahia, Brazil)

Title: Non-singular inflation with vacuum decay

Abstract:

A semi-classical analysis of vacuum energy in the expanding spacetime suggests that the cosmological term decays with time, with a concomitant matter production. For early times, the corresponding cosmological solution has no initial singularity, existing since an infinite past. During an infinitely long period we have a quasi-de Sitter, inflationary universe, with H ˜ 1. However, at a given time, the expansion undertakes a phase transition, with H and Lambda decreasing to nearly zero in a few Planck times, producing a huge amount of radiation. On the other hand, the late-time scenario is similar to the standard model, with the radiation phase followed by a dust one, which tends asymptotically to a de Sitter universe, with vacuum dominating again.

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Casas, Alberto (UAM, Madrid)

Title: Running Spectral Index as a Probe of Physics at High Scales

Abstract:

We explore inflaton potentials well motivated by particle physics which can accomodate WMAP data, focussing on a large class of models: those with flat tree-level potential lifted by radiative corrections, which cause the slow rolling of the inflaton and the running of n. This includes typical hybrid inflation models. In the small-coupling regime the predictions for the size and running of n are remarkably neat, e.g. -dn/dln k=(n-1)^2 << 1. We also examine the effect of thresholds of new physics in the shape of the potential (e.g. through non-renormalizable operators) and thus in the inflationary physics, in particular in the running of the spectral index.

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Casini Horacio (CA Bariloche, Argentina)

Title: The entanglement entropy c-theorem

Abstract:

The combination of Lorentz symmetry and the strong subbaditive property of the entropy leads to a c-theorem for the entanglement entropy in 1+1 dimensions. We present the associated c-functions for free fields and compare them with the Zamolodchikov's ones. We discuss the various difficulties which obstacle the naive generalizations of the theorem to higher dimensions.

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Catena, Ricardo (DESY-Hamburg, Germany )

Title: A frame-invariant approach to Scalar-Tensor Cosmology

Abstract:

Scalar-Tensor theories of gravity can be formulated in different frames, most notably, the Einstein and the Jordan one. While some debate still persists in the literature on the physical status of the different frames, a frame transformation amounts to a change of units, and then should not affect physical results. We analyze the issue in a cosmological context. In particular, we define all the relevant observables (redshift, distances, cross-sections, ...) in terms of frame-independent quantities. Then, we give a frame-independent formulation of the Boltzmann equation, and outline its use in relevant examples such as particle freeze-out and the evolution of the CMB photon distribution function. Finally, we derive the gravitational equations for the frame-independent quantities at first order in perturbation theory. From a practical point of view, the present approach allows the simultaneous implementation of the good aspects of the two frames in a clear and straightforward way.

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de Berredo-Peixoto, Guilherme (UDESC, Brazil)

Title: Renormalization group in higher derivative quantum gravity: new developments

Abstract:

Higher derivative Quantum Gravity is one of the most relevant models for studying quantum aspects of gravitation. We investigate the role of the Gauss-Bonnet term for the renormalization group in an arbitrary dimension, for both conformal and general versions of the theory. The cancellation of the quantum effects of the Gauss-Bonnet term in the n = 4 limit represent an efficient test for the correctness of previous calculations and also resolves a long-standing problem concerning the role of topological term in quantum gravity. In the framework of n = 4 - e renormalization group we discovered a number of new and nontrivial fixed points, some of them UV stable. However, the validity of these new fixed points is restricted by the region of small e. Out of this region the 4 - e renormalization group is spoiled by an extensive (essentially stronger than in n = 4 case) gauge fixing ambiguity.

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Title:Ghosts, Instabilities, and Superluminal Propagation in Modified Gravity Models and Gauss-Bonnet cosmologies

Abstract:

I consider Modified Gravity models involving inverse powers of fourth-order curvature invariants and Gauss-Bonnet cosmology. Using these models' equivalence to the theory of a scalar field
coupled to a linear combination of the invariants, I investigate the properties of the propagating modes. Even in the case for which the fourth derivative terms in the field equations vanish,
I find that the second derivative terms can give rise to ghosts, instabilities, and superluminal propagation speeds. I establish the conditions which the theories must satisfy in order to avoid
these problems in Friedmann backgrounds, and show that the late-time attractor solutions are generically afflicted by superluminally propagating tensor or scalar modes.

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Dobado, Antonio (UCM, Madrid)

Title: Some Model Independent Phenomenological Consequences of Flexible Brane Worlds

Abstract:

In this talk we will review the main properties of brane-world models with low tension. Starting from very general principles it is possible to obtain an effective action from which we can derive the cross sections for the relevant high energy processes and from them, to set bounds on the different parameters appearing in these models. In addition we will see how they provide a WIMP candidate for dark matter in a natural way, and finally we will discuss the constraints coming from the precision test of the SM and the muon anomalous magnetic moment.

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Dodelson, Scott (Fermilab/Chicago U, US)

Title: Gravitational Lensing

Abstract:

Light does not travel through the universe in straight lines. Over- and under-dense regions deflect photons and these deflections can build up to produce measurable effects. For example, even if Type Ia Supernovae were exact standard candles, their observed brightnesses would differ due to gravitational lensing. In this case, the magnitude of an object is affected by lensing. In other cases, objects' shapes are affected. I will discuss what can be learned about cosmology from these distortions.

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Elizalde, Emilio (ICE & IEEC, Barcelona)

Title: Quantum Vacuum Fluctuations and the Cosmological Constant

Abstract:

Zeta function regularization techniques are used for the calculation of the contribution of the vacuum energy of the quantum fields pervading the universe to the cosmological constant (cc). Naive calculations of the absolute contributions of all known fields lead to a value which is off by roughly 120 orders of magnitude, as compared with the results obtained from observational fits, what is known as the {\it new cosmological constant problem}. This is very difficult to solve and we are not going to address such issue directly. What we do consider are the {\it additional} contributions to the cc that may come from the possibly non-trivial topology of space and from specific boundary conditions imposed on braneworld models (kind of Casimir effects at a cosmological scale). Assuming one will be able to prove (in the future) that the ground value of the cc is zero (as some have always suspected), we will then be left with this incremental value coming from the topology or BCs. We show that this value acquires the correct order of magnitude ---corresponding to the one coming from the observed acceleration in the expansion of our universe--- in a number of reasonable situations involving small and large compactified scales and/or brane BCs.

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Erdem, Recai (Izmir Inst. of Technology,Turkey)

Title: A symmetry for vanishing cosmological constant

Abstract:

In a previous study (R. Erdem, PLB 621 (2005) 11 ) I had shown that a non-zero cosmological constant may be forbidden by a symmetry which replaces the usual coordinates to imaginary coordinates. In this study I give a more conventional realization of this symmetry. In this study the multiplication of the coordinates by the imaginary number i in the literature is replaced by the multiplication of the metric tensor by minus one. This realization of the symmetry as well forbids a bulk cosmological constant and selects out 2(2n + 1) dimensional spaces. On contrary to its previous realization the symmetry, without any need for its extension, also forbids a possible cosmological constant term which may arise from the extra dimensional curvature scalar provided that the space is taken as the union of two 2(2n + 1) dimensional spaces where the usual 4-dimensional space lies at the intersection of these spaces. It is shown that this symmetry may be realized as translations in the extra dimensions of a nonorientable space. A possible relation of this symmetry to the E-parity symmetry of Linde is also pointed out.

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Fabris Julio César (UFES - Brazil)

Title: Evolution of scalar perturbations and the possible end of the phantom menace

Abstract:

The fitting of the supernova type Ia data seems to favour a Universe dominated by a fluid which violates all energy conditions. For this reason, this fluid is called a phantom fluid. We review the evidences for this phantom scenario. Then, we analyse the evolution of scalar perturbations in a Universe dominated by a phantom fluid. It comes out that, under certain conditions, the scalar perturbations grow at all scales, leading to a very inhomogenous Universe. This may change the later behaviour of the cosmic evolution, and perhaps avoiding the big rip characteristic of the a Universe dominated by a phantom fluid.

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Fernández Faedo, Antón (UAM, Madrid)

Title: Vacuum Polarization in Extra Dimensions

Abstract:

We study how to define the one loop vacuum polarization function of a gauge theory in higher dimensions both from the extra dimensional and the four dimensional with the KK tower points of view . We compare the boson masses calculated in both pictures.

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Ferrer, Efrain (Western Illinois U,US)

Title: Paramagnetism in Compact Stars

Abstract:

It is quite plausible that color superconductivity occurs in the inner regions of neutron stars. At the same time, it is known that strong magnetic fields exist in the interior of compact stars. In this talk we will discuss the effects of an external magnetic field in the gluon dynamics of a color superconductor with three massless quark flavors. We show that the long-range component of the external magnetic field that penetrates the color flavor locking phase produces an instability for values larger than the corresponding charged gluons'Meissner masses. As a consequence, the ground state is restructured through the condensation of charged gluon vortices. Under the vortex currents the applied magnetic field is increased to values which depend on the pmplitude of the gluon condensate. The paramagnetic properties of the color superconductor we are reporting can be relevant fot the physics of compact stars.

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Gaite, Jose (IMAFF - CSIC, Madrid)

Title: Scale invariance of cosmic structure

Abstract:

There is evidence of a scale-invariant matter distribution on scales that reach more than 10 Megaparsecs. However, the relevant features of this distribution are controversial; in particular, the precise realization of scale invariance is a subject of debate. We present several models of large scale structure, namely, fractal or multifractal models and models of dark-matter halos or voids, and we review evidence of scale invariance in recent observations of the galaxy distribution, in particular, the Sloan Digital Sky Survey and observations of the Local Volume. We try to discern fractal features in them. We propose a model of fractal distributions of halos that is based on a multifractal model as the best model. Finally, according the this model, we analyse a recent N-body simulation and draw conclusions on structure formation: it seems to be driven to a dynamical multifractal attractor. This conclusion provides support for previous studies of structure formation by means of the renormalization group within a statistical hydrodynamics formulation.

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Garattini, Remo (U of Bergamo, Italy )

Title: Multi gravity and space time foam

Abstract:

A multi gravity model is here considered to approach the cosmological constant problem. The one loop effective action in a large N Schwarzschild wormhole background is here used to compute the cosmological constant. It is shown that the expression of the Zero Point Energy (ZPE) is equivalent to the one computed by means of a variational approach. To handle with ZPE divergences, we use the zeta function regularization. The regularization is closely related to the subtraction procedure appearing in the computation of Casimir energy in a curved background. A renormalization procedure is introduced to remove the infinities together with a renormalization group equation.

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Garcia-Bellido, Juan (UAM, Madrid)

Title: A gauge-invariant inflaton in the MSSM

Abstract:

All the necessary ingredients for successful inflation are present in the flat direction of the MSSM. We show that out of many gauge invariant combinations of squarks, sleptons and Higgses, there are two directions, LLe, and udd, which are promising candidates for the inflaton. The model predicts more than 10^3 e-foldings with an inflationary scale of H = 1 - 10 GeV, provides a tilted spectrum with an amplitude of delta_H \sim 10^-5 and a negligible tensor perturbation. The temperature of
the thermalized plasma could be as low as 1 - 10 TeV. Parts of the inflaton potential can be determined independently of cosmology by future particle physics experiments

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Garcia-Cuadrado, Gloria (IEEC, Barcelona)

Title:General Relic Gravitational Waves production mechanism in the Pre Big Bang Scenario

Abstract:

We will summarize the general mechanism of gravitational waves production and then particularize to the specific case of the so-called Pre Big Bang Scenario, a cosmological theory derived from String theory, which is able to extend the history of the Universe far beyond the Big Bang.In this new setting, the universe begins in the asymptotic past (the Pre big Bang Era) in the low-energy, weakly- coupled vacuum state described by the Low Energy String Effective Action; then driven by small fluctuations about this vacuum state, the Universe enters a run-away evolution (collapse in the so-called conformally related Einstein frame ) heading to a phase of strong coupling and high curvature, the String Regime, which in some sense is called to replace the Big Bang Singularity. After this regime is finished, the Universe "re-enters" the conventional evolution leading to the radiation dominated era.We will examine the production of gravitons in this general framework and discuss some interesting features about the model.

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Garny, Mathias (Technische U Munich, Germany)

Title: Leptonic Dark Energy and Baryogenesis

Abstract:

A baryo-symmetric baryogenesis scenario is presented, where a dynamical complex scalar field is responsible both for dark energy and the generation of the observed baryon asymmetry. The difference of baryon~($B$) and lepton~($L$) number is conserved in such a way that the $B$$-$$L$ asymmetry in the standard model sector is compensated by an asymmetry of opposite sign stored in the dark energy sector. Therefore, a toy-model is introduced in which a complex quintessence field carries a $B$$-$$L$ asymmetry at late times. The produced baryon asymmetry in the visible sector is determined for a large range of initial conditions and shown to be compatible with the observed order of magnitude. While the size of the generated asymmetry depends on details of the underlying inflationary model, it turns out to be independent of the reheating temperature in many cases.

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Garriga, Jaume (UB, Barcelona)

Title: Bubble universes and signals from before

Abstract:

Our FRW universe might be contained inside of a single bubble which nucleated in a pre-existing false vacuum phase. I will review the calculation of perturbations imprinted by the false vacuum (and by the bubble dynamics) on our observable patch. Quantum fluctuations of the bubble wall might give a detectable signal in gravity waves at the lowest multipoles, although this would require a rather lucky combination of parameters. I will also discuss some phenomenological consequences of the perturbations, such as the randomization of light fields in the FRW slices.

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Gaztañaga, Enrique (IEEC/CSIC, Barcelona)

Title: Cross-correlation of CMB with local structures: WMAP vs SDSS.

Abstract:

Recent studies by a number of independent collaborations, have correlated the CMB temperatures measured by the WMAP satellite with different galaxy surveys that trace the local matter distribution with light from the whole range of the electromagnetic spectrum: radio, far-infrared, optical and X-ray surveys. The new data systematically finds positive correlations, indicating a rapid slow down in the growth of structure in the universe. This provides independent new evidence for a dark cosmos, away from EdS universe.

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Grífols, Antoni (UAB/IFAE, Barcelona)

Title: Scalar dark matter and stability of cold stars

Abstract:

In a medium composed of scalar particles with non-zero mass, the range of Van-der-Waals-type scalar mediated interactions among nucleons becomes infinite when the medium makes a transition to a Bose-Einstein condensed phase. We explore this phenomenon in an astrophysical context. Namely, we study the effect of a scalar dark matter background on the equilibrium of degenerate stars.In particular we focus on white dwarfs and the changes induced in their masses and in their radii.

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Gu, Je-An (National Taiwan U )

Title: Accelerating Expansion from Inhomogeneities?

Abstract:

It is the common consensus that the expansion of a universe always slows down if the gravity provided by the energy sources therein is attractive. To examine this point we find counter-examples for a spherically symmetric dust fluid described by the Lemaitre-Tolman-Bondi solution. As suggested by these counter-intuitive examples, the effects of inhomogeneities on the evolution of the space-time geometry (such as the cosmic evolution) should be restudied, and the intuition about general relativity is yet to be built.

Guberina, Branko (Rudjer Boskovic Inst, Croatia)

Title:Renormalization group running cosmologies - from a scale setting to holographic dark energy

Abstract:

A scale-dependent cosmological constant Lambda and Newton's constant G emerge naturally in quantum field theory in a curved space-time background leading to renormalization group running cosmologies. A scale-setting procedure is discussed in these cosmological models and the interpretation of the scale is emphasized. This setup introduces dark energy without invoking quintessence-like fields and can be applied into a variety of problems. The scale-dependent Lambda and G are also naturally incorporated into the generalized holographic dark energy model, and applied to different aspects of cosmology.

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Gusin, Pawel (U of Silesia, Poland)

Title: Inflation conditions for non-BPS D-branes

Abstract:

In order to derive inflation from string theory one has to solve two problems: stabilization moduli and next find a potential which is responsible for inflation. The D-brane models partially solve the above problems. We investigate the potential on non-BPS Dp-brane obtained from tachyon potential and DBI-like effective action for time depending embeddings. We make the ansatz: this potential is considered as a potential for scalar fields (tachyon and embedding) coupled to a brane gravity. In this way we get a scalar field theory on the world-volume of the non-BPS Dp-brane. The dynamics and conditions for inflation on the world-volume are obtained. We also estimate in the Euclidean spacetime (for p=3) the tunneling probability from local minimum (false vacuum) to global minimum (true vacuum).

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Guth, Alan (MIT, US)

Title: Eternal Inflation and its Implications

Abstract:

After some 25 years, the inflationary paradigm continues to be an extremely successful explanation for many properties of our universe: its size, its expansion, its uniformity, its near-critical mass density, the absence of magnetic monopoles, and the properties of the density perturbations now being observed in the cosmic background radiation. In addition to helping us understand the universe that we see, however, inflation generically predicts that there are an infinite number of other "pocket universes" besides the one that we live in. Even though we do not expect to see these other universes, our understanding of their existence has important implications for our theoretical framework.

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Horvat, Raul (Rudjer Boskovic Inst, Croatia)

Title:Cosmic coincidences and relic neutrinos

Abstract: A simple phenomenological description for the energy transfer between a variable cosmological constant and a fluid of relic neutrinos in an expanding universe can account for a near coincidence between the neutrino and dark energy densities to hold over a significant portion of the history of the universe. Although such a cosmological setup may promote neutrinos to mass-varying particles (both slow and quick neutrino mass changing with the expansion of the universe can be naturally implemented in the model), it works equally well for static neutrino masses too.

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Hung, Pham Q. (U. of Virginia, US)

Title: A model of dark energy and dark matter

Abstract:

A dynamical model for the dark energy is presented in which the ``quintessence'' field is the axion, $a_Z$, of a spontaneously broken global $U(1)_{A}^{(Z)}$ symmetry whose potential is induced by the instantons of a new gauge group $SU(2)_Z$. The $SU(2)_Z$ coupling becomes large at a scale $\Lambda_Z \sim 10^{-3}\,eV$ starting from an initial value $M$ at high energy which is of the order of the Standard Model (SM) couplings at the same scale, suggesting an unification of $SU(2)_Z$ and the SM at a comparable scale. We present a scenario in which $a_Z$ is trapped in a false vacuum characterized by an energy density $\sim (10^{-3}\,eV)^4$. The lifetime of this false vacuum is estimated to be extremely large. Other estimates relevant to the ``coincidence issue'' include the ages of the universe when the $a_Z$ potential became effective, when the acceleration ``began'' and when the energy density of the false vacuum became comparable to that of (baryonic and non-baryonic) matter. Other cosmological consequences include a possible candidate for the weakly interacting (WIMP) Cold Dark Matter as well as a scenario for leptogenesis.

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Incera, Vivian (Western Illinois U, US)

Title: Color superconductivity and Magnetic Field: Strange Bed Fellows in the Core of Neutron Stars?

Abstract:

It is well-known that magnetic fields and superconductivity in metallic bodies do not get along well. However, that is not the case in color superconductivity, a state reached by quark matter at densities as high as those existing in the cores of neutron stars. This talk will focus on the effects of an external magnetic field in a color superconductor. In three-flavors color superconductivity the electromagnetic field mixes up with one gluon to give rise to a long-range, ?in medium? electromagnetic field. Because of this, an externally applied magnetic field penetrates the color superconductor as a ?modified? magnetic field. At weak magnetic fields, the preferred phase for three massless flavors is the Color-Flavor-Locking phase. However, a sufficiently strong magnetic field can strengthen the binding energy of the quark-quark pairs formed by quarks with non zero ?modified? electric charges to the point that the structure and magnitude of the gap is changed producing the so-called Magnetic Color-Flavor-Locking phase. Details of the MCFL phase will be presented and possible astrophysical implications will be outlined.

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Janssen, Tomas (Utrecht U, Netherlands)

Title: Instabilities in the Nonsymmetric theory of Gravitation.

Abstract:

We consider an extension of General relativity known as the nonsymmetric theory of gravitation (NGT). By constructing an explicit example it is shown that the theory one would naively expect is unstable. We postulate a stable, consistent form of the theory and study it's cosmological influence. In particulat the possibility that NGT solves the dark matter problem will be discussed.

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Kamenshchik, Alexander (U Bologna, Italy)

Title: Cosmological Landscape and Euclidean Quantum Gravity

Abstract:

We revisit the old idea of Euclidean quantum gravity alternative to theconstruction of the pure Hartle-Hawking quantum state. Creation from nothing is described by the density matrix given by the Euclidean path integral. Its calculation with back reaction of quantum matter properlytaken into account suggests a novel picture of the early quantum Universe.

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Kasuya, Shinta (Kanagawa U, Japan)

Title: Towards the robustness of Affleck-Dine mechanism

Abstract:

The key ingredient for successful Affleck-Dine baryogensis is how to obtain a large VEV in the first place. It is usually achieved by the negative Hubble-induced mass term, but here we seek for a successful mechanism when the Hubble-induced mass term is positive and its coefficient is of order unity.

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Korzynski, Mikolaj (Warsaw U, Poland )

Title:Can dark matter in Galaxies be explained by relativistic corrections?

Abstract:

I will discuss the feasibility of explaining the dark matter phenomenon in galaxies by relativistic corrections to Newtonian equations of motion. In particular, I will discuss why the recent model described by Cooperstock and Tieu cannot work.

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Latorre, Jose Ignacio (UB, Barcelona)

Title: Area law and Quantum Information

Abstract:

Area law for the entropy of the ground state of a quantum field theoryfollows from basic principles in quantum information and locality ofinteractions. Consequences of this result for renormalization groupon quantum states and the representation of entangled quantum statesare discussed.

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Linde, Andrei (Stanford U, USA)

Title: Inflation and String Cosmology

Abstract:

I will describe the recent progress in inflationary theory and in the theory of dark energy in the context of string theory

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Linder, Eric (LBNL, Berkeley, US)

Title: Dark Energy, Gravity, and Cosmology

Abstract:

Recent developments in understanding the influence of dark energy dynamics on cosmological observables have led to several insights in how to reveal the nature of dark energy. This includes the categorization of many physics models for the dark energy into either freezing or thawing behavior, recognition of differences from the inflation scenario, and methods for robustly distinguishing a physical dark energy from a modification of gravitational physics. These have definite consequences for probing dark energy, such as prescription of the relative precision needed for dynamics measurements, the need for probes of both cosmological expansion and large scale structure growth, and how dark energy microphysics can contribute a theory-induced systematics limit on many techniques.

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Litim, Daniel (U Southampton, UK)

Title: RG running of gravitational couplings in four and higher dimensions

Abstract:

We study euclidean quantum gravity using functional renormalisation group techniques. In the Einstein-Hilbert theory, we identify a non-trivial ultraviolet fixed point in four- and higher dimensional gravity. If the the fixed point persists in extended studies, quantum gravity can well be formulated as a fundamental theory in the metric field. We discuss the corresponding phase diagram, and implications of the fixed point on the running gravitational coupling and the cosmological constant. Possible signatures of the fixed point behaviour are indicated.

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López-Fogliani, Daniel Elbio (UAM, Madrid)

Title: Neutralino Dark Matter in the NMSSM

Abstract:

We analyse the direct detection of neutralino dark matter in the framework of the Next-to-Minimal Supersymmetric Standard Model. Taking into account all the available constraints from LEPII, we compute the neutralino-nucleon cross section and compare the resuls with the sensitivity of detectors. We also study the relic abundance of neutralinos, comparing with WMAP results.

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Losic, Bojan (U of Alberta, Canada)

Title: Leading order gravitational backreactions in de Sitter

Abstract:

We discuss results which show that the mere act of coupling a linear scalar field to gravity in de Sitter spacetime severely restricts the symmetry of quantum states the linear field can possess, namely to only those which are fully de Sitter (SO(4,1)) invariant.

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Love, Sherwin (Purdue U, US)

Title: Aspects of Spontaneous Breaking of Anti- de Sitter Space Isometries

Abstract:

Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the global and local symmetries of $AdS_{d+1}$ space due to the embedding of an $AdS_{d}$ brane. The resulting action is an $SO(2,d)$ invariant $AdS$ form of the Einstein-Hilbert action, which in addition to the $AdS_d$ gravitational vielbein, also includes a massive vector field localized on the brane. Its long wavelength dynamics is the same as a massive Abelian vector field coupled to gravity in $AdS_d$ space. The isometries of $AdS_5$ space and supersymmetric $AdS_5\otimes S_1$ space are also nonlinearly realized on four dimensional Minkowski space. The resultant effective actions in terms of the Nambu-Goldstone modes are constructed. The dilatonic mode governing the motion of the Minkowski space probe brane into the covolume of supersymmetric $AdS_5$ space is found to be unstable and the bulk of the $AdS_5$ space is unable to sustain the brane. No such instablility appears in the non-supersymmetric case.

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Maeda, Kei-ichi (Waseda U, Tokyo, Japan)

Title: Collision of branes and reheating of the Universe

Abstract:

We study collision of two branes (domain walls) in 5-dimensional Minkowski spacetime and in asymptoticaliy Anti de Sitter spacetime. This may provide the reheating mechanism of an ekpyrotic (or cyclic) brane universe, in which two BPS branes collide and evolve into a hot big bang universe. We numerically solve dynamics of a scalar field composing the domain wall and evaluate a production rate of particles confined in the domain wall at the collision of two domain walls. The energy density of created particles is given as r ~20 g4 Nb ~mh4 where g is a coupling constant of particles to a domain-wall scalar field, Nb is the number of bounces at the collision and mh is a fundamental mass scale of the domain wall. It does not depend on the width d of the domain wall, although the typical energy scale of created particles is given by w~1/d. The reheating temperature is evaluated as T R= 0.88 g Nb 1/4. In order to have the baryogenesis at the electro-weak energy scale the fundamental mass scale is constrained as mh > 1.1x 107 GeV for g ~ 10-5. We also analyze the effect of a negative cosmological term in the bulk to the collision process and the evolution of our universe.

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Makler, Martín (CBPQ, Brazil)

Title: The Quest for Dark Matter and Dark Energy Unification

Abstract:

In recent years, a wealth of astrophysical data, when interpreted in the light of general relativity, has lead to an emerging consensus among cosmologists: the dynamics of the universe is dominated by a dark matter component responsible for the clustering of luminous matter (accounting for almost a third of the universe's total density), as well as a negative pressure dark energy component that drives the present phase of accelerated expansion (and provides about two thirds of the total density). Since none of these two unknown components has been detected in laboratory experiments, one may ask whether dark matter and dark energy really are two distinct physical entities, or if the observed clustering and the accelerated expansion could be produced by a single component. This last alternative has motivated the search for models of unifying dark matter, also known as quartessence (since only one extra component is needed besides ``baryons'', neutrinos, and photons). The most popular quartessence candidate has been the Chaplygin gas and generalizations thereof, however several other models were proposed and investigated in the literature. Considerable attention is being devoted to explore observational predictions that can be contrasted to the data to constrain or even discard such models. We have shown that a wide class of adiabatic quartessence models, namely those with a convex equation of state, can be ruled out by observations of the matter distribution in large scales. Models with a given type of intrinsic adiabatic perturbations are still allowed by current data. However they might leave a clear signature in the weak lensing skewness that could be detectable with the next generation of experiments to measure weak lensing by the large-scale structure, such as the one that will be performed by the Dark Energy Survey. Another class compatible with the data considered so far is given by models where the equation of state has a sharp transition from pressureless to a constant negative pressure. Nevertheless, they affect structures in nonlinear scales and might leave an imprint on galaxy clusters. Here we report our progress in the investigation of the quartessence scenario, presenting recent results on the nonlinear evolution of quartessence as well as on the computation of the weak lensing convergence field, providing an account of the current status of such models.

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Martínez, Manel (IFAE, Barcelona)

Title: Cosmology with VHE Gamma Ray Telescopes

Abstract:

The observation of the universe in the VHE gamma ray domain with the new generation of Cherenkov Telescopes is producing new measurements with a direct implication for cosmology. The present results and the future prospects will be discussed.

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Mazzitelli, Francisco Diego (U. Buenos Aires, Argentina)

Title: Renormalized stress tensor for trans-Planckian cosmology

Abstract:

Finite expressions for the mean value of the stress tensor corresponding to a scalar field with a generalized dispersion relation in a Friedmann-Robertson-Walker universe are obtained using adiabatic renormalization. Formally divergent integrals are evaluated by means of dimensional regularization. The renormalization procedure is shown to be equivalent to a redefinition of the cosmological constant and the Newton constant in the semiclassical Einstein equations. These renormalized equations should be the starting point discuss backreaction effects in trans-planckian cosmology.

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Melkumova, Elena (Moscow State U, Russia)

Title: Dilaton and axion bremsstrhlung from colliding strings

Abstract:

We calculate classically axion and dilaton radiation under collision of two unexcited long strings, which move in parallel planes in flat space-time being inclined with respect to each other. Under certain conditions on the velocity and the inclination angle the point of the minimal separation between the strings moves with the superluminal velocity and Cherenkov radiation is produced. In four space-time dimensions there is dilaton and axion radiation and no gravitational radiation. In higher dimensions all massless fields are emitted. Some cosmological implications are discussed.

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Mersini, Laura (U Noth Carolina, US)

Title: Gravity, Thermodynamics and the Landscape

Abstract:

I will discuss the issue of the Initial Conditions for inflation, within the context of the landscape of string theory. The inclusion of the dynamics of the gravitational degrees of freedom drives the initial inflationary patch into an out-of equilibrium state. We show that the phase space of the initial conditions is not conserved, ergodicity is broken due to quantum entaglement, which is why when statistical probability arguments based on equliibrium and ergodicity assumptions are used, they lead to paradoxes. This radically different approach from the current ones in the literature, based on a dynamic selection of the initial conditions of a system with matter and gravitational degrees of freedom, can help to reconcile the friction between the inflationary initial conditions and the 2nd law of thermodynamic, a.k.a. the arrow of time.

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Miquel, Ramon (LBNL and ICREA/IFAE, Barcelona)

Title: Cosmology with type-Ia supernovae: present and future

Abstract:

I will review the use of type-Ia supernovae (SNe) for cosmological studies. After briefly recalling the by-now classical measurements that led in 1998 to the discovery of the accelerating universe, I will describe current and planned type-Ia SNe surveys, with special emphasis on their physics reach in the presence of systematic uncertainties, which will be dominant in nearly all cases.

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Mohanty, Subhendra (UAB, Barcelona)

Title: Thermal effects in inflation power spectrum

Abstract:

If inflation was preceded by a hot radiation era then there is a stimulated emission of the inflatons into the thermal distribution of existing inflatons. This distorts the power spectrum of density perturbations during inflation which has a measurable signature in the CMB anisotropy. There will also be a similar distortion in the graviton power spectrum which will enhance the B-mode polarizations at large angles. This enhancement of the B-mode polarization will be most pronounced in Warm Inflation models.

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Mukhanov, Slava (LMU, Muenchen, Germany)

Title: Enhancing gravitational waves from inflation

Abstract:

(not provided)

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Muñoz, Carlos (UAM, Madrid)

Title: Supersymmetric dark matter and its possible detection

Abstract:

I will discuss the theoretical predictions for the direct detection of neutralino dark matter in underground experiments, through elastic scattering with nuclei in a material. Likewise, the indirect detection in satellites and telescopes, through the gamma rays produced by the neutralino annihilation in our galactic halo, will be analyzed. A comparison between both kinds of detection will be carried out.

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Neves, Rui (U of Algarve, Portugal)

Title: Braneworlds, Conformal Fields and the Graviton

Abstract:

We investigate the dynamics of Randall-Sundrum AdS5 braneworlds with 5-dimensional conformal matter fields. In the scenario with a compact fifth dimension the class of conformal fields with weight -4 is associated with exact 5-dimensional geometries which are stable under radion field perturbations and describe on the brane the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy. We analyze graviton and Kaluza-Klein mode flutuations around this class of background solutions and discuss the physical bounds imposed by the particle mass hierarchy, the localization ofgravity in the vicinity of the brane and the low energy gravitational interaction.

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Odintsov, Sergei (ICREA/IEEC, Barcelona)

Title: Dark energy and modified gravities.

Abstract:

The modification of gravity as gravitational alternative for dark energy and universe acceleration is considered. The number of modified gravities is discussed, where solar system tests maybe successfully fulfilled. It is shown how various regimes (cosmological constant, quintessence or phantom) as well as possible transitions (deceleration/acceleration, crossing of phantom divide) maybe realized in modified gravities. Finally, the comparison of such approach with the inhomogeneous equation of state of the universe is done.

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Panda, Sukanda (UAM, Madrid)

Title: Finite Temperature Effects and Axion Cosmology

Abstract:

We investigate the impact of finite temperature effects on axions in the context of cosmology. The temperature dependence of the mass and decay constant are modeled analogous to pions. For the two interesting cases considered here, we find that the temperature effects do lead to changes relevant for detailed and precise abundance and rate calculations.

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Parentani, Renaud (U de Paris-Sud, France)

Title: Inflationary Spectra and Violations of Bell inequalities

Abstract:

The inflationary scenario succesfully accounts for the observed properties of primordial density fluctuations in terms of amplification of vacuum fluctuations. In spite of the macroscopic character of the final amplitudes,we show that the standard inflationary distribution still exhibits inherently quantum mechanical correlations (which cannot be mimicked by any classical stochastic ensemble). We propose a Gedanken experiment for which certain Bell inequalities are violated. We then show that the violation persists provided that the decoherence lies below a certain non-vanishing threshold. Finally, there exists a higher threshold above which no violation of any Bell inequalities can occur. In this case only the corresponding distributions can be interpreted as stochastic ensembles of classical fluctuations.

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Pelinson, Ana (U Sao Paulo, Brazil)

Title: Constraints on dark energy from the observed density fluctuations spectrum

Abstract:

One of the greatest challenges in cosmology today is to determine the nature of dark energy, the source of the observed present acceleration of the universe. We show here that the bias parameter at redshift $z\sim 0$, $b^2(0)$, is a powerful tool to discard dark energy models which are not viable. The final data set of the 2dF Galaxy Redshift Survey indicate that the bias factor $b^2(0)$ for $L_{\ast}$ galaxies is $b_{\Lambda CDM}^2(0)\simeq 1.06$ in a flat $\Lambda$CDM universe. Analytic models for the evolution of $b^2(z)$ as a function of redshift have appeared in the literature. Normalizing these models to $0.9 \leq b^2(z=0) \leq 1.1$, we find that viable dark energy models also require at $z\sim 0$ a bias factor $0.9 \leq b^2(z=0) \leq 1.1$. Using this requirement, a matter density $\Omega_M^0=0.28\pm 0.02$ and the assumption that the universe is approximately flat, we find that the vacuum metamorphosis model (VMM) and the popular brane-world model (BWM), both of which are used to explain dark energy, can be discarded. Relaxing the $\Omega_M^0$ requirement, we find that a $10\%$ agreement with $b^2\simeq 1.0$ at $z\simeq 0$ can be obtained if $\Omega_M^0\simeq 0.36$ for the VMM and $\Omega_M^0\simeq 0.73$ for the BWM. These values for $\Omega_M^0$ are not consistent with observations. Using previous constraints from SNIa data we also exclude another known dark energy model, the supergravity (SUGRA) model, which deviates from $b^2\simeq 1.0$ at $z\simeq 0$ by $38\%$.

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Pavón, Diego (UAB, Barcelona)

Title: Holographic dark energy and late cosmic acceleration

Abstract:

It has been persuasively argued that the number of the effective degrees of freedom of a macroscopic system is proportional to its area rather than to its volume. This entail interesting consequences for cosmology. Here we focus on explaining how this “ holographic principle” may account for the present state of accelerated expansion of the Universe and significantly alleviate the coincidence problem, both for spatially- flat and non-spatially flat cosmologies.

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Percacci, Roberto (SISSA, Trieste)

Title: The fixed point of higher derivative gravity

Abstract:

Several authors have shown long ago that higher derivative gravity is perturbatively renormalizable and asymptotically free. This required a vanishing cosmological constant. On the other hand Weinberg conjectured that gravity may be renormalizable in a nonperturbative sense ("asymptotically safe"). A recent calculation shows that higher derivative gravity, with a cosmological constant, is asymptotically safe at a nontrivial fixed point.

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Polarski, David (U Montpellier II, France)

Title: Scalar-tensor Dark Energy models

Abstract:

We will review various aspects of scalar-tensor Dark Energy models. Special emphasis will be on the possibility to have Phantom Dark Energy in these models.

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Prokopec, Tomislav (Utrecht U)

Title: Quantum corrections to the scalar propagator in de Sitter space

Abstract:

We argue that the one loop RG improved analysis of the scalar field theory in de Sitter space suggests a way to obtain a de Sitter invariant scalar propagator, even when classically the scalar field is massless and minimally coupled.

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Quiros, Mariano (ICREA/IFAE, Barcelona)

Title Electroweak baryogenesis

Abstract:

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Raffelt, Georg (MPI, Munich)

Title: Axions: Motivation, Cosmological Role and New Searches

Abstract:

The Peccei-Quinn mechanism remains an attractive solution of the CP problem of strong interactions. Its prediction of axions opens a unique window of opportunity to search for new physics and provides an attractive dark matter candidate. The role of axions as a possible hot or cold dark matter candidate is reviewed as well as recent axion searches and new cosmological and experimental limits.

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Reuter, Martin (U of Mainz, Germany)

Title: Recent Developments in Asymptotically Safe Quantum Gravity

Abstract:

The asymptotic safety scenario in gravity is briefly reviewed and our present knowledge about the nonperturbative renormalization group behavior of Quantum Einstein Gravity (QEG) is summarized. Possible implications for astrophysics and cosmology are discussed, and the fractal properties of the QEG spacetimes are described.

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Rojo, Juan (UB, Barcelona)

Title: Extraction of the atmosferic neutrino fluxes from atmosferic data.

Abstract:

Astrophysical neutrino detectors have the potential to become an important tool for precision cosmology. A precise knowledge of atmosferic neutrino flux are very relevant for astrophysical neutrino detectors, both since they are the main background and they are used for detector calibration. These fluxes are computed from Monte Carlo simulations. We present an alternative approach to the determination of these fluxes based on the direct extraction from the experimental data on neutrino event rates.

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Roura, Albert (LANL, US)

Title: Quantum metric fluctuations in black hole spacetimes

Abstract:

The quantum fluctuations of a black hole spacetime are studied within a low-energy effective field theory approach to quantum gravity. Our approach accounts for both intrinsic metric fluctuations and those induced by matter fields interacting with the gravitational field. Here we will concentrate on spherically symmetric fluctuations of the black hole horizon. Our results suggest that for a sufficiently massive evaporating black hole, fluctuations can accumulate over time and become significant well before reaching Planckian scales.Additional subtleties concerning horizon fluctuations will be briefly described and a natural way to probe quantum metric fluctuations will be proposed.

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Ross, Andreas (U of Massachusetts Amherst,US )

Title:Spin Effects in the Effective Quantum Field Theory of General Relativity

Abstract:

The calculation of gravitational scattering of particles with spin in the framework of effective quantum field theory of general relativity is presented. We show that the spin independent long range quantum and classical corrections to the scattering potential are universal for different spin configurations. That leads us to suspect this universality to be true for arbitrary spins. Furthermore we give the leading corrections to spin-orbit coupling and spin-spin coupling and a comparison with scattering in QED is made.

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Russo, Jorge (UB, Barcelona)

Title: Black hole formation from collisions of cosmic fundamental strings

Abstract:

We develop the general formalism for joining, splitting and interconnection of closed and open strings. As an application, we study examples of fundamental cosmic string collisions leading to gravitational collapse. We find that the interconnection of two strings of equal and opposite maximal angular momentum and arbitrarily large mass generically leads to the formation of black holes, provided their relative velocity is small enough.

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Salvatori, Matteo (UAM, Madrid)

Title: Symmetry breaking from flux compactification

Abstract:

Motivated by the electroweak hierarchy problem, we consider a background magnetic flux living on compact, toroidal, extra dimensions, with the four-dimensional scalar fields being gauge boson components in full space. For SU(N), we determine analytically the possible field configurations of stable vacua, and the symmetry breaking patterns. From the 4-dimensional point of view, the system responds dynamically to the magnetic background by an infinite chain of vacuum expectation values, so as to reach an stable vacuum. The equivalence between flux compactification and constant boundary conditions - either Scherk-Schwarz or toron-like - is established.

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Sarkar, Subir (Oxford U, UK)

Title: What have we learnt about inflation from WMAP?

Abstract:

Precision observations of CMB anisotropies in conjunction with studies of large-scale structure have supposedly confirmed the indication from the SN Ia Hubble diagram that the universe is dominated by some form of dark energy with negative pressure. This conclusion is based however on the assumption that the spectrum of primordial fluctuations is scale-free. Looked at more closely the WMAP data suggests that this is not in fact the case and physical models of inflation based on supergravity provide a plausible mechanism for imprinting features in the scalar perturbation spectrum. The CMB and LSS data can then be fitted without the need for dark energy, but with ~eV mass neutrinos in addition to cold dark matter.

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Schimd, Carlo (Saclay, France)

Title: Tracking quintessence by cosmic shear - Constraints from VIRMOS-Descart and CFHTLS and future prospects

Abstract:

Among several descriptions of the dark energy, a quintessence scalar field provides a simple, well-defined alternative to the cosmological constant able to account for the dynamics of the universe at low and high redshift. After showing the advantages of such a realization of the dark energy with respect to parametrizations of its equation of state, I present recent results based on a cosmic shear analysis, for the first time using VIRMOS-Descart and CFHTLS data to investigate such kind of models. Several questions about the constraints on dark energy come out, notably the relevance of a proper description of the non-linear regime of structures formation, the caution needed when combining with other cosmological observables such as SnIa and CMB, the dependence on systematics, for instance the accuracy of photometric redshift or luminosity distance measurements. Finally, I will discuss the power of (space-based) wide surveys to study the dark energy sector.

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Seto, Osamu (U. Sussex, UK)

Title: D-term inflation with suppressed cosmic strings and lowered n_s

Abstract:

We investigated a simple D-term inflation with taking account of higher order corrections in the potential, particularly, in the Kahler potential. These terms make an inflationary potential flatter than logarithmic in the case without these higher correction terms, through 1-loop radiative corrections. As a result, the mass per unit length of cosmic strings formed after inflation can be suppressed and its corresponding $G\mu$ is $ several \times 10^{-7}$. In addition, the change of the potential slope leads simultaneously a more tilted scalar spectral index $n_s \simeq 0.96-0.97$ than that in the model without these corrections $n_s \simeq 0.98$.

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Shapiro, Ilya (UFJF, Brazil)

Title: Cosmological Constant Problems and Renormalization Group

Abstract:

The cosmological constant problem emerges as a kind of hierarchy problem when the Quantum Field Theory methods are applied to derive the induced gravitational action. At the tree level one meets the induced vacuum energy of enormous magnitude and, in order to obtain a reasonable value of the observable cosmological constant, one has to perform an extremely precise fine-tuning of the vacuum counterpart. We review a few of the existing approaches to the problem and pay special attention to the ones involving the renormalization group. The quantum effects of massive matter fields may produce a slight violation of the fine-tuning and therefore lead to the scale dependent cosmological constant with interesting and potentially detectable cosmological implications.

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Silk, Joe (Oxford U, UK)

Title: The Cosmic Microwave Background: Past, Present and Future

Abstract: The cosmic microwave background is an unexcelled probe of the early universe. The temperature fluctuations have led to unprecedented improvements in the accuracy of determining the parameters of cosmology. I will review the history, present status and future experiments in this field.

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Solà, Joan (UB, Barcelona)

Title: Cosmologies with running parameters and dynamical cosmon

Abstract:

We discuss the cosmologies with a variable cosmological term (including perhaps a variable Newton's gravitational coupling). The ultimate origin of this variability could be the general RG running of parameters in QFT in curved spacetime. We find that by extending the composite structure of the DE with the inclusion of a dynamical cosmon, X, a new class of cosmological models emerge (LXCDM) in which the cosmic coincidence of matter and DE densities could be explained in a natural way.

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Starobinsky, Alexei (Landau Inst. Moscow)

Title: Stochastic inflation and perturbations

Abstract:

Primordial scalar (density) perturbations and gravitational waves are the main observable quantities which remained from very early stages of evolution of our Universe. Predictions of the simplest (one-parametric) class of inflationary models for the power spectrum and statistics of these perturbations have been successfully confirmed by observations which are beginning now to exclude some models from this class. Still, the three historically first models proposed in 1980-1983 remain alive (among many more recent ones). I review some recent results on primordial perturbations including exact solutions for inflaton field potentials producing a) the exactly flat (Harrison-Zeldovich) adiabatic spectrum, b) a constant tensor/scalar ratio. Also, the question how to obtain a correct rms value of inflaton field fluctuations from the formalism of stochastic inflation is considered. In most variants of the inflationary scenario, very strong inhomogeneity at very large scales much exceeding the present Hubble radius is expected, including the existence of an infinite number of separate post-inflationary universes. However, I argue that it may affect the evolution of the observable part of our Universe through a renormalization of parameters of the isotropic background only.

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Stefancic, Hrvoje (UB, Barcelona)

Title:What is in the black box of dark energy: variable cosmological parameters or multiple (interacting) components?

Abstract:

The unknown nature of dark energy reflects itself in a number of puzzling properties of the present Universe, comprising the coincidence problem of the presently comparable energy densities of nonrelativistic matter and dark energy and the peculiarities of the possible evolution of the dark energy equation of state. A solution of these problems can be sought by considering dark energy as an effective description of alternative cosmological models. An effective dark energy behavior of the cosmological models with variable parameters as well as the composite models of dark energy is presented. Implications of these cosmological problems to the coincidence problem and a possible cosmological constant boundary crossing are discussed.

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Stephan-Otto, Christian (Tufts U, US)

Title: Optimal constraints on dark energy evolution

Abstract:

We discuss a model-independent method to study the possible evolution of dark energy. Optimal estimates of the DE equation of state are extracted from current SNe data following a principal components approach. Then, a Bayesian model selection method is used to rank the resulting models, as well as comparing them with commonly used parametrizations. Although data seem to prefer a cosmological constant, several models are only moderately disfavored: constant w, w~a, w~z and the two-parameter models introduced. Among two-parameter models, our optimized ones seem to be slightly preferred by data, however, we reach no conclusion on the possible evolution of dark energy.

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Tanabe, Makoto (Waseda U, Japan)

Title: Stationary spacetime with time-like or null Killing vectorfrom intersecting M-branes.

Abstract:

We study a stationary black brane in M/superstring theory. Assuming BPS-type relations between the first-order derivatives of metric functions, we present general stationary black brane solutions with a time-like or null Killing vector for the Einstein equations in $D$- dimensions. The solutions are given by a few independent harmonic equations (and plus the Poisson equation). General solutions are constructed by superposition of a complete set of those harmonic functions. Using the hyperspherical coordinate system for a conformally flat base space, we explicitly give the solutions in 11- dimensional M theory for the case with M2$Â¥perp$M5 intersecting branes and a traveling wave with null KIlling vector. Compactifying these solutions into five dimensions, we show that these solutions include the BMPV black hole and the Brinkmann wave solution, and those extension to non-BPS ones. With time-like Killing vector spacetime we find M2$Â¥perp$M2$Â¥perp$M2 intersecting brane with Chern- Simons term in 11-dimensional M theory. After the compactification we find the supersymmetric black ring solution in hyperbipolar coordinate in five dimension.

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Tillman, Philip (U of Pittsburgh, US)

Title: The Klein-Gordon equation on curved space-times: an application of deformation quantization

Abstract:

Fedosov quantization is a method for deriving the set of observables of finitely many particles on the phase-space of any manifold.
In particular the focus will be on Lorentzian manifolds. The connection between standard covariant quantization is explained. The classical invariant 4-momentum squared is promoted to an operator equation that is equivalent to a Klein-Gordon (KG) equation. Recent results will be summarized fo dS/AdS, Schwarzschild, and Kerr-Newman space-times.

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Toporensky, Aleksey (Moscow U, Russia)

Title: Cosmological dynamics with vacuum polarization

Abstract:

We consider de Sitter stability in modified gravity theories with respect to vacuum polarization. We assume that an analog of the Friedmann equation in the theory under consideration has the form $H=f(\rho)$, where $H$ is the Hubble parameter,$\rho$ is the matter density. After adding the vacuum polarization terms, this algebraic equation becomes a differential one. We write down eigenvalues of corresponding dynamical system in a de Sitter point, and show that stability of de Sitter solution depends on the sign of $df/d\rho$. A de Sitter point located at a phantom branch(where $df/d\rho < 0$) is unstable with respect to vacuum polarization.

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Townsend, Paul (Cambrige U, UK)

Title:Fake Susy and Pseudo Susy: a Domain-Wall/Cosmology Duality

Abstract: All gravitational domain walls supported by scalar fields are shown to satisfy first-order equations that imply the existence of `fake' Killing spinors, provided only that the wall has constant non-positive curvature. All flat or closed FLRW cosmologies are similarly shown to satisfy first-order equations that imply the existence of ``pseudo'' Killing spinors. These results are related by a Domain-Wall/Cosmology `duality'. The implications for stability of domain walls, and the relation to the Hamilton-Jocobi formulation of cosnmology, will be discussed.''

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Valle, José (IFIC, Valencia)

Title: Neutrinos in astroparticle physics: status and prospects

Abstract:

I briefly review the status of neutrino oscillations and the challenges for precision determination of neutrino properties. I also discuss the theoretical options to understand neutrino masses & mixings from first principles and the resulting experimental tests.

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Van Proeyen, Antoine (K.U. Leuven, Belgium)

Title: Effective supergravity descriptions of superstring cosmology

Abstract:

String theory has succeeded in the last years to provide models for early universe cosmology. Most relevant effects for cosmology can be described by effective supergravity actions. We discuss features of these supergravity descriptions related to inflation and to cosmic strings.

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Vikman, Alexander (LMU Munich, Germany )

Title: Supersonic inflation

Abstract:

It is well known that in manifestly Lorentz invariant theories with nontrivial kinetic terms, perturbations around some classical backgrounds can travel faster than light. These exotic "supersonic" models may have interesting consequences for cosmology and astrophysics. In particular, one can show that in such theories the contribution of the gravitational waves to the CMB fluctuations can be substantially larger than that in standard inflationary models. This increase of the tensor-to-scalar perturbation ratio leads to a larger B-component of the CMB polarization, thus making the prospects for future detection much more promising. The other important consequence of the considered model is a higher energy scale of inflation and hence higher reheating temperature compared to a simple inflation. Finally I will discuss causality and stability of these models.

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Vilenkin, Alex (Tufts U, USA)

Title: Probabilities in the landscape

Abstract:

Inflationary cosmology, combined with recent ideas in string theory, leads to the picture of a "multiverse", involving an infinite ensemble of "pocket universes" characterized by different values of the constants of nature. I shall discuss how the probability distribution for the constants can be calculated in this ensemble, with applications to the cosmological constant Lambda and the amplitude of density perturbations Q.

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Wetterich, Christof (U Heidelberg, Germany)

Title:Quintessence - a fifth force from variation of the fundamental scale?

Abstract:

Dark energy - a homogeneously distributed cosmic energy density - seems to explain various cosmological observations. We explore the hypothesis that a dynamical dark energy arises from the evolution of a scalar field which is related to a time-varying fundamental mass scale. A dilatation anomaly induced by quantum fluctuations could explain the small value of the present dark energy. An observable consequence of such a scenario results in "early dark energy " contributing a few percent to the energy density of the Universe even at high redshift. Quintessence would be related to a new "fundamental" macroscopic force and induce a small time variation of fundamental constants.

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Zanella, Juan (U Buenos Aires)

Title: Inflation and the nonequilibrium renormalization group

Abstract:

We study the spectrum of primordial fluctuations and the scale dependence of the inflaton decay rate in theories with a self-interacting inflaton field [1,2]. To this effect, we consider the inflationary expansion as a scaling transformation operating on the field modes [3]. We compute the resulting spectrum of perturbations and the inflaton decay constant by applying nonequilibrium renormalization group techniques.

Zsembinski, Gabriel (IFAE-UAB)

Title: Unified model for inflation and dark energy

Abstract:

We present a model with a complex and a real scalar fields and a
potential whose symmetry is explicitly broken by Planck-scale
physics. For exponentially small breaking, the model accounts for
the period of inflation in the early universe and for the period
of acceleration of the late universe.