Krzysztof Bielas
(Institute of Physics, University of Silesia, Poland)
08/09/2015, 12:30
We use the 'local weakening of logic in a spacetime' as a mathematical tool suitable also for building cosmological models. The models extend the regular spacetime solutions of Einstein equations towards solutions with certain spacetime singularities. Such models are also natural for addressing the renormalization questions of various quantum field theories. We discuss this issue...
Mateja Gosenca
(Astronomy Centre, School of Mathematical and Physical Sciences, University of Sussex, United Kingdom)
08/09/2015, 12:31
N-body simulations normally use equations of Newtonian dynamics to evolve particles and fields forward in time. On galactic scales and at times late enough for velocities and gradients of fields to be small this turns out to be an extremely good approximation. However, in modified gravity models, at earlier times when neutrinos are relativistic, or on much larger scales, evolving relativistic...
Ludwik Kostro
(Ateneum-University in Gdansk, Poland)
08/09/2015, 12:32
The Lambda Units determined by three Einstein's constants: velocity of light, his gravitational constant and his lambda cosmological constant will be introduced. Some of them are already used in relativistic cosmology e.g. lambda density of mass and the pressure of the physical vacuum . Other Units like e.g. lambda quantum of action i.e. the inverse of the product of the mentioned above three...
Manuel Arca Sedda
(University of Rome La Sapienza, Italy)
08/09/2015, 12:33
In this contribution we discuss how the centres of galaxy clusters evolve in time, showing the results of a series of direct N-body modelling at high resolution.
In particular, we followed the evolution of a galaxy cluster with a mass of around 10^14 solar masses in four different configurations: 1) isolated cluster; 2) cluster subjected to the action of Dark Energy; 3) cluster composed of...
Giulia Cusin
(Département de Physique Théorique and Center for Astroparticle Physics, University of Geneva, Switzerland)
08/09/2015, 12:34
We introduce a new formalism to study perturbations of Hassan-Rosen bigravity theory, around general backgrounds for the two dynamical metrics. In particular, we derive the general expression for the mass term and we explicitly compute it for some cosmological settings. We study in detail tensor perturbations in branch-one bigravity using this formalism. We show that the tensor sector is...
Luisa Jaime
(Institute for Theoretical Physics, Heidelberg University, Germany)
08/09/2015, 12:35
We introduce a different approach in f(R) gravity. Our approach avoids the mapping to scalar tensor theories using the Ricci scalar itself as an 'extra' degree of freedom. In this talk we will present this formalism and we will analyze the equation of state (EOS) of the geometric dark energy related with the extra terms in f(R), including the comparison of several EOS that have been proposed...
Nobuyoshi Ohta
(Department of Physics, Kinki University, Japan)
08/09/2015, 12:36
We study gravitational theories with a cosmological constant and the Gauss-Bonnet curvature squared term and analyze the possibility of de Sitter expanding spacetime with a constant internal space. We find that there are two branches of the de Sitter solutions: Both the curvature of the internal space and the cosmological constant are (1) positive and (2) negative. From the stability analysis,...
Yasuho Yamashita
(Yukawa Institute for Theoritical Physics, Japan)
08/09/2015, 12:37
Recently the ghost-free bigravity, the gravitational theory which contains two metrics interacting each other, is constructed by tuning the interaction terms to remove Boulware-Deser ghost. Using this model, we can realize the late-time cosmic accelerating expansion and the gravitational wave has a charasteristic feature.
However, we have no idea what is the mechanism which tunes the...
Sebastian Zell
(Department of Physics, Ludwig-Maximilians-Universitaet Muenchen, Germany)
08/09/2015, 12:38
We follow the corpuscular approach proposed by Dvali and Gomez, in which N universally characterizes gravitational backgrounds (with N = (Mp)^2/Λ for de Sitter spacetime). In doing so, we explicitly draw a fully quantum picture of the background metric in the limit of weak gravity. Using coherent states in each mode, we show that it can be understood as collective effect of soft,...
Martina Donnari
(Department of Physics, University of Rome La Sapienza, Italy)
08/09/2015, 12:39
Systems of selfgravitating Fermions constitute a topic of great interest in astrophysics, due to the wide range of applications, and are used also to explain dark matter in galaxies and clusters of galaxies. Here, we study the gravitational equilibrium of spherical models describing a semidegenerate collisionless gas. The Fermi-Dirac distribution function, modified by a cutoff term in order to...
Sebastian Trojanowski
(National Centre for Nuclear Research, Poland)
08/09/2015, 12:40
I will examine the relic abundance of supersymmetric dark matter in a scenario where the reheating temperature T_R of the Universe after inflation is low, in the range of tens or of hundreds of GeV. To this end I will solve the Boltzmann equation during and after the period of reheating, taking into account cosmological as well as collider constraints, in particular the recent Higgs boson...
Andrew Williams
(National Centre for Nuclear Research, Poland)
08/09/2015, 12:41
We analyse the sensitivity of the future Cherenkov Telescope Array (CTA) experiment to dark matter annihilations in the galactic centre using the most up to date instrument response functions and background simulation model provided by the CTA Collaboration. We systematically examine the different statistical methods for setting limits using CTA and provide a realistic assessment of the...
Sam Young
(Physics and Astronomy, University of Sussex, United Kingdom)
08/09/2015, 12:42
Primordial black holes may have formed very early on during the radiation dominated era in the early universe, and are normally used to probe the small scale perturbations formed towards the end of inflation. I will present a method by which the large scale perturbations in the number density of primordial black holes may be used to place tight constraints on non-gaussianity if PBHs account...
Yugo Abe
(Shinshu University, Japan)
08/09/2015, 12:44
We study whether the inflation is realized based on the radion gauge-Higgs potential obtained from the one-loop calculation in the 5-dimensional gravity coupled to a U(1) gauge theory.
We show that the gauge-Higgs can give rise to inflation in accord with the astrophysical data and the radion plays a role in fixing the values of physical parameters.
We clarify the reason why the radion...
Lukasz Dulny
(Faculty of Physics, University of Warsaw, Poland)
08/09/2015, 12:45
Equations of motion in slow roll inflationary models with two scalar fields for scalar perturbations metrics were analysed for an example of turning valley in scalar potential with non-canonical kinetic term. The impact of the multi-scale dynamics on the sub-horizon evolution of the perturbations was studied with a special emphasis on the (lack of) decoupling of the large scale modes and...
Vera-Maria Enckell
(Department of Physics, University of Helsinki, Finland)
08/09/2015, 12:47
It has been shown that Higgs inflation could be realized even if the Higgs potential has a negative energy minimum separating the inflationary part from the low-energy SM regime. The precise shape of the potential is dictated by the running of the couplings which necessarily differs from SM predictions at high-energies. We explore how the high-energy running affects the details of the...
Olga Czerwinska
(University of Warsaw, Poland)
08/09/2015, 12:48
It is known that time-dependent vacuum expectation value of the background field causes the production of particles, in the expanding universe this process is also influenced by the time-dependence of the scale factor. Poster would present the general mechanism of particle production in time-varying backgrounds with the impact of rescattering emphasised, also in models with more than one...
Taro Kunimitsu
(RESCEU University of Tokyo, Japan)
08/09/2015, 12:49
We systematically show that in potential driven generalized G-inflation models, quantum corrections coming from new physics at the strong coupling scale can be avoided, while producing observable tensor modes. The effective action can be approximated by the tree level action, and as a result, these models are internally consistent, despite the fact that we introduced new mass scales below the...
Stefano Orani
(University of Basel, Switzerland)
08/09/2015, 12:51
In 'hilltop inflation', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the 'hilltop') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that...
Mauro Pieroni
(AstroParticle and Cosmology laboratory, Paris Diderot University-Paris 7, France)
08/09/2015, 12:52
In some recent papers it was proved that the cosmological evolution of a scalar field in a potential can be descirbed in terms of a renormalisation group equation. The slow rolling regime of the inflaton can be compared with the slow departure from a fixed point of the beta function in the RG group context.
This can be seen as an effective approach to the problem in the sense that the...
Christopher Harman
(University of Sussex, United Kingdom)
08/09/2015, 12:53
Taking on a new perspective of the electroweak phase transition, we investigate a quantity called the one loop zero temperature vacuum energy difference. This quantity allows us to address all manner of features that are known to give rise to a strong first order electroweak phase transition. Our study is conducted using six extensions to the Standard Model of varying complexity,...
Kohji Yajima
(Department of Physics, Rikkyo University, Japan)
08/09/2015, 12:54
We consider a squared term of Weyl tensor in the Einstein-Hilbert’s action. It is one kind of the theories about higher curvature invariants in the action as quantum corrections. In general, such additional terms generate ghost degrees of freedom. But the theory we consider here is ghost free by breaking local Lorentz symmetry. Using this theory, we consider gravitational waves from slow-roll...
Laura Taddei
(ITP Heidelberg, Germany)
08/09/2015, 12:55
Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution
was standard CDM in the past and that the present matter density and power spectrum
normalization are the same as in a CDM model. Here we examine how the constraints change
when these assumptions are lifted. We focus in particular on the parameter Y (also called G_effective ) that
quanties the...
David Weir
(University of Stavanger, Norway)
08/09/2015, 12:56
