TITLES and ABSTRACTS First Name: Andrea Surname: Addazi

TITLES AND ABSTRACTS

First Name: Andrea Surname: Addazi Afﬁliation: Fudan University (Shanghai)

Quantum Vacuum & Quantum black holes: two aspects of the same question ------Quantum vacuum and Quantum black holes may be considered as two aspects of the same problem. First of all, we will show how virtual black hole pairs provide a planckian contribution to the vacuum energy which screens the contribution coming from Standard Model vacuum energy. Second, we will move on the possible relation of dark energy and (Anti)evaporation instabilities in the framework of f(R)-gravity, In this case, a model for cosmology may provide insightful intuitions on the black hole thermodynamics and the information paradox.

First Name: Imanol Surname: Albarran Afﬁliation: Universidade da Beira Interior

The quantum realm of the "Little Sibling" of the Big Rip singularity ------We analyse the quantum behaviour of the Little Sibling of the Big Rip singularity (LSBR). The quantisation is carried within the geometrodynamical approach given by the Wheeler- DeWitt(WDW)equation. The classical model is based on a Friedmann-Lemaître- Robertson-Walker Universe filled by a perfect fluid that can be mapped to a scalar field with phantom character. We analyse the WDW equation in two setups. In the fi rst step, we consider the scale factor as the single degree of freedom, which from a classical perspective parametrises both the geometry and the matter content given by the perfect fluid. We then solve the WDW equation within a WKB approximation, for two factor ordering choices. On the second approach, we consider the WD equation with two degrees of freedom: the scale factor and a scalar fi eld. We solve the WDW equation, with the Laplace-Beltrami factor-ordering, using a Born-Oppenheimer approximation. In both approaches, we impose the DeWitt (DW) condition as a potential criterion for singularity avoidance. We conclude that in all the cases analysed the DW condition can be verified, which might be an indication that the LSBR can be avoided or smoothed in the quantum approach.

First Name: Oleg Surname: Antipin Afﬁliation: Institut Rudjer Boskovic

Revisiting the decoupling effects in the running of the Cosmological Constant ------We discuss the decoupling effects associated with heavy particles in the renormalisation group running of the vacuum energy in a mass-dependent renormalization scheme. We find the running of the vacuum energy stemming from the Higgs condensate in the entire energy range and show that it behaves as expected from the simple dimensional arguments meaning that it exhibits the quadratic sensitivity to the mass of the heavy particles in the infrared regime. The consequence of such a running to the fine-tuning problem with the measured value of the Cosmological Constant is analyzed and the constraint on the mass spectrum of a given model is derived. We show that in the Standard Model (SM) this fine-tuning constraint is not satisfied while in the massless theories this constraint formally coincides with the well known Veltman condition. We also provide a remarkably simple extension of the SM where saturation of this constraint enables us to predict the radiative Higgs mass correctly. Generalization to constant curvature spaces is also given.

First Name: Manuel Surname: Asorey Afﬁliation: Universidad de Zaragoza

Infrared and ultraviolet problems in QFT and Quantum Gravity ------

First Name: Alexander Surname: Balakin Afﬁliation: Kazan Federal University, Institute of Physics

Rheological models of the cosmic dark fluid ------Based on analogy with classical theory of thermo-visco-elasticity, we formulate rheological models of evolution of the cosmic dark fluid. In the context of homogeneous cosmological models, the simplest rheological equations of state for the interacting dark energy and dark matter take into account the time delay in the evolutionary processes. Mathematically, these time delay effects can be described in terms of convective derivatives and convolution integrals of the Volterra type, thus the equations of state are considered to be the integro-differential equations. Applications to the Friedmann-type models and Bianchi-I type models are considered; the five-parameter family of exact solutions is obtained, classified and analyzed.

First Name: José Surname: Beltran Jimenez Afﬁliation: Universidad Autónoma de Madrid

Theoretical aspects of Born-Infeld inspired gravity with cosmological applications. ------Abstract: In order to regularize the energy of point-like charged particles, Born and Infeld introduced a modification of the Maxwell Lagrangian that naturally imposes an upper bound on electromagnetic fields. Similar ideas can be applied to gravity to resolve the GR singularities. I will discuss some general theoretical aspects of these theories (which are shared by more general metric-affine theories) as well as some cosmological applications, with emphasis in non-singular and inflationary solutions.

First Name: Mariam Surname: Bouhmadi-López Afﬁliation: University of the Basque Country

Cosmological perturbations of the late-time Universe. ------We carry out an analysis of the cosmological perturbations in general relativity for different models which are good candidates to describe the current acceleration of the Universe. These different set-ups are described classically by perfect ﬂuids with a quintessence or a phantom nature and represent deviations from the most widely accepted ΛCDM model. In the phantom case, each of the models under study induce different future singularities or abrupt events known as (i) Big Rip, (ii) Little Rip and (iii) Little Sibling of the Big Rip. With the aim to ﬁnd possible footprints of the different scenarios, we not only obtain the evolution of the cosmological scalar perturbations but also calculate the matter power spectrum for each model. We constrain observationally these models using several measurements of the growth rate function, more precisely fσ8, and compare our results with the observational ones.

First Name: Antonio Surname: Capolupo Afﬁliation: Università di Salerno

Dark Matter and Dark Energy Induced by Vacuum Condensates ------It is shown that the vacuum condensate induced bymany phenomena behaves as a perfect fluid which, under particular conditions, has zero or negative pressure. In particular, the condensates of thermal states of fields in curved space and of mixed particles have been analyzed. It is shown that the thermal states with the cosmic microwave radiation temperature and the Unruh and the Hawking radiations give negligible contributions to the critical energy density of the universe, while the thermal vacuum of the intercluster medium could contribute to the dark matter, together with the vacuum energy of fields in curved space-time and of mixed neutrinos. Moreover, a component of the dark energy can be represented by the vacuum of axion-like particles mixed with photons and superpartners of neutrinos.The formal analogy among the systems characterized by the condensates can open new scenarios in the possibility of detecting the dark components of the universe in table top experiments.

First Name: Salvatore Surname: Capozziello Afﬁliation: Università Federico II di Napoli

Addressing the missing matter problem in galaxies through a new fundamental gravitational radius ------We demonstrate that the existence of a Noether symmetry in f(R) theories of gravity gives rise to a further gravitational radius, besides the standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it is possible to explain the baryonic Tully-Fisher relation and the rotation curve of gas-rich galaxies without the dark matter hypothesis.

First Name: Po-Wen Surname: Chang Affiliation: National Taiwan University Rapid Oscillation of Gravitational Constant in the Scalar-Tensor Theory of Gravity: the early-time constraints on its induced energy density from cosmology ------In the scalar-tensor theory of gravity, the concept of gravitational constant G can be replaced with a scalar field non-minimally coupled to gravity. It turns out to be an additional degree of freedom compared to general relativity and is possible to induce periodic oscillations in G by a homogeneous and isotropic massive scalar field ϕ. In this research, we show that the equation of motion of ϕ can be cast into a fairly graceful formula and the dissipation rate of its effective energy density could behave differently during the cosmic evolution, which depends on the strength of non-minimal coupling, mass of ϕ and the cosmic expansion rate. Realizing the dynamics of ϕ, we find that we could obtain a loose upper bound of the effective energy density from cosmology by assuming specific properties of the G oscillation at present. We then give phenomenological constraints on the effective energy density in a broad parameter space. The constraints could be served as a potential guide to construct the models with non-minimal coupling.

First Name: Che-Yu Surname: Chen Afﬁliation: National Taiwan University, Taiwan

The Mimetic Born-Infeld Gravity: The Primordial Cosmos and Spherically Symmetric Solutions ------The Eddington-inspired-Born-Infeld (EiBI) model is reformulated within the mimetic approach. In the presence of a mimetic ﬁeld, the model contains non-trivial vacuum solutions. We study a realistic primordial vacuum universe and we prove the existence of regular solutions. Besides, the linear instabilities in the EiBI model are found to be avoidable for some bouncing solutions. For a vacuum, static and spherically symmetric geometry, a new branch of solutions in which the black hole singularity is replaced with a lightlike singularity is found.

First Name: Stefano Surname: Chinaglia Afﬁliation: INFN - TIFPA

A model of Regular Black Hole ------We discuss a star generated by some matter fluid and show that, under suitable conditions on the fluid itself, the model is able to produce regular black hole solutions. We also show it satisfies the Null Energy Condition and the Weak Energy Condition.

First Name: Aimeric Surname: Colléaux Afﬁliation: University of Trento INFN-TIFPA

Rational Regular Black holes in non-polynomial gravity ------Using non-polynomial gravity scalars (see [S. Deser, O. Sarioglu, B. Tekin, 2007]), we found an action that includes arbitrary higher order corrections to the Einstein-Hilbert one, and that gives, for spherical symmetry, rational regular black hole solutions. Non-polynomial gravity scalars consist of non-polynomial combination of curvature invariants that are nontheless polynomial for spherically symmetric spacetimes. In our case, they also lead to second order equations of motion in spherical symmetry.

First Name: Álvaro Surname: de la Cruz-Dombriz Afﬁliation: Gravity & Cosmology Group, University of Cape Town

Towards new constraints in extended theories of gravity: cosmography, g-evolution, neutron stars and gravitational waves ------Abstract: In the context of scalar-tensor gravity theories, the apparent mass of neutron stars as seen from an observer at infinity is numerically calculable but requires careful matching, first at the star’s edge, between interior and exterior solutions, none of them being totally Schwarzschild-like but presenting instead small oscillations of the curvature scalar R ; and second at large radii, where the Newtonian potential is used to identify the mass of the neutron star. Thus, for the same equation of state, this mass definition is always larger than its general relativistic counterpart and consequently, star radii are in general smaller than in General Relativity, which can give an observational handle on such classes of models at the astrophysical level. Finally, because neutron stars masses can be much larger than General Relativity counterparts, the total energy available for radiating gravitational waves could be of order several solar masses, and thus a merger of these stars constitutes an interesting wave source. Model-independent methods in cosmology, N-body simulations and theoretical predictions in strong-gravity regimes have become essentials tool in order to deal with an increasing number of theoretical alternatives for explaining several open issues in the cosmic history. In principle, this provides a way of testing the ΛCDM cosmological paradigm under different assumptions and to rule out whole classes of competing theories. In this talk I will present some of the latest progress and shortcomings in the cosmographic approaches for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H(z) differential age compilations. I will also sketch a recent line of full N-body simulation technique modifying g-evolution to accommodate effects from higher- order theories and finally, I will provide a flavour on the phenomenology of neutron stars and gravitational waves constraints once the Einsteinian paradigm is abandoned.

First Name: Mariafelicia Surname: De Laurentis Afﬁliation: Goethe University

Observational signatures of spherically-symmetric black hole spacetimes ------The most precise and stringent strong-ﬁeld tests of General Relativity performed so far, as well as the most accurate determination of orbits, have been achieved through pulsar timing, albeit not yet in the Galactic Centre. Pulsars are compact, rotating neutron stars which act like cosmic lighthouses, possessing some of the strongest gravitational ﬁelds in the known Universe. When a pulsar is found in a binary orbit, it can be considered a test mass free falling in the gravitational potential of its companion. This free fall can then be compared with the predictions of General Relativity, but also any other theory of gravity. A a binary system comprising a supermassive black hole and a pulsar orbiting around it is studied. In particular, taking into account a general spherically symmetric metric, analytic calculations for the geodesic motion and the possible deviations with respect to the standard Schwarzschild case of General Relativity are presented. The advance at periastron and the orbital period are studied with an aim to identify corrections to General Relativity. A discussion concerning the motion of compact objects around the candidate supermassive black hole (Saggitariuus A*) in the Galactic Centre is reported.

First Name: Emilio Surname: Elizalde Afﬁliation: Institute of Space Sciences IEEC-CSIC

Bing Bang, new singularities, and a renormalization group improved, uniﬁed accelerating scenario ------

First Name: Antonino Surname: Flachi Afﬁliation: Keio University

Quantum Vacuum and Black Holes ------

First Name: Drazen Surname: Glavan Afﬁliation: University of Warsaw

Electrodynamic Effects of Inflationary Gravitons ------Photons are conformally coupled to gravity and therefore do not get produced due to cosmological expansion, while gravitons are not and do get produced a lot due to the expansion of the primordial Universe. Since gravitons couple universally to all matter fields they can induce sizeable effects to conformally coupled fields through loop corrections. I will present computations in two different gauges for the one-loop graviton corrections to photon vacuum polarization in de Sitter spacetime. This is used to quantum correct Maxwell equations, and I will present two cases, (i) correction to dynamical photons, and (ii) correction to the Coulomb force between two point charges. The corrections in both cases exhibit secular growth. Gauge dependence of the results will be discussed. This talk is mainly based on: arXiv:1609.00386 [gr-qc] arXiv:1504.00894 [gr-qc] arXiv:1308.3453 [gr-qc]

First Name: Dragan Surname: Hajdukovic Afﬁliation: Institute of Physics, Astrophysics and Cosmology

Quantum vacuum fluctuations and the Universe ------We argue that a single hypothesis that “quantum vacuum fluctuations are virtual gravitational dipoles” has the potential to explain the greatest mysteries of our time: what is the nature of what we call dark matter, what is the nature of what we call dark energy and why matter dominates antimatter in the Universe. According to this emerging model of the Universe, the only matter-energy content of the Universe is the Standard Model matter (i.e. matter composed from quarks and leptons interacting through the exchange of gauge bosons). The phenomena usually attributed to hypothetical dark matter, may be considered as a consequence of the local gravitational polarization of the quantum vacuum by the immersed baryonic matter; apparently, the galactic halo of dark matter can be replaced by the halo of the polarized quantum vacuum. Globally quantum vacuum may be considered as a cosmological fluid which during expansion of the Universe converts from a fluid with negative pressure, allowing an accelerated expansion of the Universe, to a fluid with zero pressure (physically it means the end of the accelerated expansion). This for the first time suggests, quantum vacuum may explain both phenomena; phenomena usually attributed to dark matter and phenomena usually attributed to dark energy. In addition, as a consequence of hypothesis of virtual gravitational dipoles together with the gravitational version of the Schwinger mechanism, we may live in a cyclic universe with cycles alternatively dominated by matter and antimatter. At least mathematically there is no initial singularity, there is no need for the cosmic inflation and there is an amusing explanation of the matter-antimatter asymmetry in the universe: our universe is dominated by matter because the previous cycle was dominated by antimatter (and the next cycle would be dominated by antimatter again). The eventual gravitational effects of the quantum vacuum “enriched” with virtual gravitational dipoles, among others can be revealed by the study of orbits of tiny satellites in trans-Neptunian binaries.

First Name: Jaume Surname: Haro Afﬁliation: Universitat Politècnica de Catalunya

Quintessential inflation at low reheating temperatures ------Some well-known and simple quintessential inflation models, obtained matching inflationary potentials with an small cosmological constant, are tested to clarify its viability. To be viables, they have to give spectral quantities that match with the current observation data provided by Planck's team, and more important, the reheating temperature obtained from the models must be low enough, in fact it has to be in the MeV regime, to avoid the production of undesired gravitational relics as gravitinos or moduli fields.

First Name: Igor Surname: Kanatchikov Afﬁliation: U. St Andrews, Scotland, UK

Precanonical quantization of gravity, quantum geometry and the cosmological constant ------I review the approach of precanonical quantization of Einstein gravity which is based on the De Donder-Weyl Hamiltonian formulation where no distinction between space and time is necessary. I show that, in the case of scalar fields and gauge fields, the results of the canonical quantizaton can be derived from precanonical quantization as a singular limiting case when the ultra-violet scale introduced by precanonical quantization is infinite. Precanonical quantizaton of gravity defines the vielbeins as partial differential operators with respect to the spin connection coefficients. The wave function defined on the space of spin connection coefficients obeys a covariant generalization of the Schroedinger equation on this space. Quantum geometry of space-time is described by a random field of spin-connection coefficients whose distribution function can be derived from the generalized Schroeddinger equation. Classical Einstein equations can be derived from the Schroedinger equation as the equations for expectation values of the corresponding operators defined by precanonical quantization. The ordering of operators consistent with the Ehrenfest theorem dictates the value of the cosmological constant in terms of the fundamental constants and the UV scale introduced by precanonical quantization.

First Name: Sugumi Surname: Kanno Afﬁliation: University of the Basque Country

Infinite violation of Bell inequalities in inflation ------One of the cornerstones of inflationary cosmology is that primordial density fluctuations have a quantum mechanical origin. However, such quantum mechanical effects were considered by most physicists to be disappeared in CMB data due to decoherence. I will apply Bell inequalities to cosmology and show that the quantum mechanical effects in an initial state of our universe increases exponentially with the number of modes to measure in inflation. This indicate that some evidence that our universe has a quantum mechanical origin may survive in CMB data even if quantum entanglement decays exponentially afterward due to decoherence.

First Name: Anna Surname: Kotanjyan Afﬁliation: Yerevan State University

Electromagnetic Casimir effect in anti de Sitter spacetime ------

First Name: Martin Surname: Krssak Afﬁliation: University of Tartu

Modified teleparallel theories ------Modified theories of gravity have recently became a popular approach to address the problem of the accelerated expansion of the Universe. However, it turns out that it is possible to modify general relativity not only in its standard formulation, but also in the so-called teleparallel formulation. The most studied modified teleparallel gravity is the so-called f(T) gravity. I will present recent results that include methods to resolve some problems that we faced in f(T) gravity and show some novel methods to formulate new modified theories.

First Name: Manuel Surname: Krämer Afﬁliation: University of Szczecin

Quantum-gravitational effects on primordial power spectra in slow-roll inflationary models ------We calculate corrections from canonical quantum gravity to the power spectra of gauge-invariant scalar and tensor perturbations during inflation. We use a direct canonical quantization of a perturbed inflationary universe model, which leads to a Wheeler-DeWitt equation. For this equation, a semiclassical Born-Oppenheimer type of approximation is applied in order to obtain a Schrödinger equation with quantum- gravitational correction terms. We carry out our calculation for a pure de Sitter universe as well as in the first slow-roll approximation. For the de Sitter case, we find that the correction terms lead to an enhancement of power on the largest scales. In the slow-roll approximation, this correction gets modified by terms proportional to the slow-roll parameters. A correction to the tensor-to-scalar ratio is also found at second order in the slow-roll parameters. Making use of the available experimental data, the magnitude of these quantum-gravitational corrections is estimated. Finally, the effects for the temperature anisotropies in the cosmic microwave background are qualitatively obtained. (joint work with David Brizuela and Claus Kiefer)

First Name: Ruth Surname: Lazkoz Afﬁliation: University of the Basque Country

Forecast and analysis of the cosmological redshift drift ------The cosmological redshift drift could lead to the next step in high-precision cosmic geometric observations, becoming a direct and irrefutable test for cosmic acceleration. In order to test the viability and possible properties of this effect, also called Sandage-Loeb (SL) test, we generate a model independent mock data set so as to compare its constraining power with that of the future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO). The performance of those data sets is analyzed by testing several cosmological models with Markov chain Monte Carlo (MCMC), both independently and combining all data sets. Final results show that, in general, SL data sets present allow for remarkable constrains on the matter density parameter today on every tested model, showing also a great complementarity with SNe and BAO data regarding dark energy (DE) parameters.

First Name: Hideki Surname: Maeda Afﬁliation: Hokkai-Gakuen University, Japan

Unitary evolution of the quantum universe with a Brown-Kuchar dust ------We study the time evolution of a wave function for the spatially flat Friedmann-Lemaitre-Robertson-Walker universe governed by the Wheeler-DeWitt equation in both analytical and numerical methods. We consider a Brown-Kuchar dust as a matter field in order to introduce a "clock" in quantum cosmology and adopt the Laplace-Beltrami operator-ordering. The Hamiltonian operator admits an infinite number of self-adjoint extensions corresponding to a one-parameter family of boundary conditions at the origin in the minisuperspace. For any value of the extension parameter in the boundary condition, the evolution of a wave function is unitary and the classical initial singularity is avoided and replaced by the big bounce in the quantum system. Exact wave functions show that the expectation value of the spatial volume of the universe obeys the classical time evolution in the late time.

First Name: Ivan Surname: de Martino Affiliation: Universidad del Pais Vasco Pulsar Timing from gravitational potential of ultra light scalar field dark matter haloes ------Light Axionic Dark Matter, motivated by string theory, is increasingly favored for the "no-WIMP era". Galaxy formation is suppressed below an Jeans scale, of $simeq 10^8 M_odot$ by setting the axion mass to, $m_B sim 10^{-22}$eV, and the large dark cores of dwarf galaxies are explained as solitons on the de-Broglie scale. The oscillating field pressure induces general relativistic time dilation in proportion to the local dark matter density and pulsars within this dense core have detectably large timing residuals, of $simeq 400nsec/(m_B/10^{-22}eV)$. More generally the pulsars imprint a pairwise Galactocentric signature that can be distinguished from an isotropic gravitational wave background. This is encouraging as many new pulsars should be discovered near the Galactic center with planned radio surveys.

First Name: Jakub Surname: Mielczarek Afﬁliation: Jagiellonian University, Cracow

Signature-change quantum cosmology ------Space-time signature change at high density has been obtained as a possible consequence of deformed space-time structures in the models of loop quantum gravity. The purpose of the talk is to provide a review discussion of implications of the effect in cosmology. Especially, the role of the characteristic problem for the mixed-type partial differential equations describing evolution of cosmological perturbations will be stressed. The issue of deﬁning a proper vacuum state for the quantum perturbations in the signature-changing cosmology will be discussed. Furthermore, our current understanding of the signature-changing quantum space-time, including the associated state of silence, will be presented.

First Name: João Surname: Morais Afﬁliation: Universidad del País Vasco / Euskal Herriko Unibertsitatea

Through an Euclidean wormhole in the Third Quantization scheme ------Within the framework of the Third Quantization, we consider the possibility that an initially cyclic baby universe can enter a stage of near de Sitter inflation by tunnelling through an Euclidean wormhole that connects the oscillating and inflationary geometries. We find the solutions for the evolution of the scale factor in the Lorentzian and Euclidean regions and calculate the probability that the baby universe indeed crosses the wormhole when it reaches its maximum size. Finally, in a simple set-up, we comment on possible signatures of the Third Quantization scheme on the CMB.

First Name: Vasilisa Surname: Nikiforova Afﬁliation: INR RAS

Self-accelerating Universe in modified gravitational theory with dynamical torsion ------The models of modified gravity with dynamical torsion are often considered as a promising candidates for the consistent infrared modified gravity. Self-accelerating solutions without explicit cosmological constant in Lagrangian were found in various gravities with dynamical torsion. However, question about the stability of self-accelerating solutions in these theories (at least at the linearized level) remained open. We consider the particular model of modified gravity with dynamical torsion. We found that this model has promising stability properties and admits a self-accelerating solution. After that we studied the stability of linear perturbations about this solution. We found that there is at least one instability in the scalar sector of perturbations, if the value of background torsion is large enough. The case of small background torsion however were found to be stable at least in the scalar sector.

First Name: Nimrod Surname: Nir Afﬁliation: Weizmann Institute of Science, Ulf Leonhardt's group

Casimir effect in planar soft wall ------Current models of the Casimir effect require renormalization in order to get meaningful results. The original Lifshitz formulation for the Casimir effect suggests a physical interpretation for the renormalization but fails to describe inhomogeneous media. However, a recent generalization of the Lifshitz theory is able to deal with planar inhomogeneous media, which also has application for curved space, because spatial geometries behave like inhomogeneous media. I will show the use of this new theory in calculating the vacuum stress of a “soft wall”. There the refractive index changes continuously between empty space and a dielectric wall, but its derivatives experience a jump. In this configuration one finds a divergence of the renormalized stress near the wall, brought about by the (idealized) jump in the derivative. The divergence is going to be softened in practice, but it still indicates a strong physical effect. I will show the calculations for the characteristic power law of the soft wall's stress in 2D and the results for 3D for various media. I will also point out a curious mathematical feature: The emergence of only prime numbers in the coefficients of the Casimir stress there.

First Name: Shin'ichi Surname: Nojiri Afﬁliation: Nagoya Univ.

Simple Model of Cosmological Constant ------Recent observations tells that the expansion of the present universe is accelerating. The accelerating expansion could be explained by a small cosmological constant, $Lambda^{1/4} sim 10^{-3},mathrm{eV}$, which can be regarded with the vacuum energy. As well-known, however, the corrections from the matters in the quantum field theory to the vacuum energy $rho_mathrm{vacuum}$ diverges and it is necessary to introduce the cutoff scale $Lambda_mathrm{cutoff}$, which might be the Planck scale, to regularize the divergence. Then the obtained value of the vacuum energy $sim Lambda_mathrm{cutoff}^4$ is be much larger than the observed value in the universe. Even if we impose the supersymmetry in the high energy, the situation is not improved. In arXiv:1601.02203, a simple model has been proposed in order to solve one of the problems related with the cosmological constant. The quantum corrections to the vacuum energy are absorbed into a redefinition of a scalar field and the quantum corrections become irrelevant to the dynamics. The model is given by a topological field theory and the model has an infinite numbers of the BRS symmetries. The BRS symmetries are, however, spontaneously broken in general. In arXiv:1702.07063, we investigate the BRS symmetry in more details and show that there is one and only one BRS symmetry which is not broken and the unitarity can be guaranteed. In the model, the quantum problem of the vacuum energy reduces to the classical problem of the initial condition. Then we investigate the cosmology given by the model and specify the region of the initial conditions which could be consistent with the evolution of the universe. We also show that there is a stable solution describing the de Sitter space-time, which may explain the accelerating expansion in the current universe.

First Name: Mohammad Surname: Nouri-Zonoz Afﬁliation: University of Tehran

The cosmological term and its interpretation in De Sitter-type spacetimes ------After introducing de Sitter -type spacetimes, it is shown that the identification of the geometric (or cosmological) term Λg_{ij} with a perfect fluid with the equation of state p = −ρ = constant, although mathematically consistent, obscures the crucial role of the dark fluid’s velocity in defining a preferred comoving coordinate system in de Sitter-type spacetimes. Therefore for a consistent interpretation of de Sitter-type spacetimes one should model the cosmological term as a perfect dark fluid. Employing this interpretation we obtain the time-dependent version of the cylindrically symmetric de Sitter-type spacetime.

First Name: Sergei Surname: Odintsov Afﬁliation: Institute of Space Scienes IEEC-CSIC and ICREA

Unifying inﬂation with dark energy epoch: the case of modiﬁed gravity ------

First Name: Cupatitzio Surname: Ramirez Afﬁliation: Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla

Quantum Cosmology of Quadratic �(�) Theories with a FRW Metric ------We study the quantum cosmology of a quadratic �(�) theory with a FRW metric, via one of its equivalent Horndeski type actions, where the dynamic of the scalar ﬁeld is induced. The classical equations of motion and the Wheeler-DeWitt equation, in their exact versions, are solved numerically. The numerical solution of the Wheeler-DeWitt equation depends strongly on the boundary conditions, which can be chosen so that the resulting wave function of the universe is normalizable and consistent with Hermitian operators.

First Name: Natascha Surname: Riahi Affiliation: University of Vienna, faculty of physics Wave packet evolution in unimodular quantum cosmology ------The unimodular theory of gravity admits a canonical quantization of minisuperspace models without the problem of time. We derive instead a kind of Schrödinger equation. We have found unitarily evolving wave packet solutions for the special case of a massless scalar field and a spatially flat Friedmann universe. We show that the longterm behaviour of the expectation values of the canonical quantities corresponds to the evolution of the classical variables. The solutions provided in an explicit example can be continued beyond the singularity at t=0, passing a finite minimal extension of the universe.

First Name: Diego Surname: Rubiera-Garcia Afﬁliation: Institute of Astrophyics, University of Lisbon

Regular black holes, wormholes and de Sitter cores from anisotropic ﬂuids ------

First Name: Jiro Surname: Soda Afﬁliation: Kobe University

Ultralight Axion in f(R) gravity ------The axion is known as a candidate for the dark matter. In particular ultralight axion can resolve small scale problems in CDM. On the other hand, f(R) gravity can explain the dark energy. Hence, it is natural to consider the ultralight axion in f(R) gravity. In this talk, we will show the coherent oscillation of the axion can be enhanced by f(R) gravity due to the resonance. We also discuss its detectability with interferometers.

First Name: Tomasz Surname: Trzesniewski Afﬁliation: University of Wroclaw

Cosmology with the compact phase space of matter ------The concept of a field theory with nonlinear (compact) phase space has recently been introduced, inspired by nontrivial geometry of the particles' phase spaces appearing in several approaches to quantum gravity. It is also motivated by the principle of finiteness of physical quantities, proposed by Born and Infeld. Among other things, this framework has been applied in the context of cosmological evolution, by considering a scalar field theory with spherical phase space, defined on the standard FRW background (i.e. general relativity itself is not modified). In the mathematical sense, the scalar field Hamiltonian is assumed to correspond to the continuous XXZ Heisenberg model of a system of spins. For the homogenous cosmology the compactness of the field's phase space turns out to be relevant at late cosmological times, when it can lead to a recollapse of universe, while at early times there is a possibility of a bounce, avoiding the initial singularity. Moreover, quantum perturbations of the field have been studied in the linear approximation but taking into account the Lorentz symmetry breaking term in the field Hamiltonian. This leads to a correction to the ordinary amplitude of perturbations and to a generalization of the Bunch-Davies vacuum state, while the inflationary spectral index remains unchanged in the leading order. The discussed framework is potentially able to bring cosmology and condensed matter physics closer together.

First Name: Kunihito Surname: Uzawa Afﬁliation: Kwansei Gakuin University

Supersymmetric M-brane solution in dynamical background ------The supersymmetry arises in certain theories of fermions coupled to gauge ﬁelds and gravity in a spacetime of eleven dimensions. The dynamical M-brane backgrounds have mainly been discussed for the class of purely bosonic solutions only, but developments involving time-dependent supersymmetric solution have made it clear that one can get more information by asking what happens on dynamical brane systems. In this presentation, we show an exact supersymmetric solution of dynamical M-brane background in the eleven-dimensional supergravity and consider applications to supersymmetric breaking, dynamics of geodesic motion and black hole physics.

First Name: Vincenzo Surname: Vitagliano Afﬁliation: CENTRA - IST, Lisbon (Portugal)

Covariant quantum corrections for the cubic Galileon ------The usual calculation of efective actions relies on some assumption about the split between background and fluctuating field variables, in principle leading to a further dependence of the results on the choice of background and gauge. Arguing that such dependence of the efective action is a by-product of the quantum fields’ dependence on the parametrization, Vilkovisky and DeWitt developed a geometrical, field-space covariant procedure to modify the usual background-field method which renders the efective action gauge- and background-independent. In this talk, I will present some modern cosmological applications of the Vilkovisky-DeWitt method.