In this talk, a review of the information that large galaxy surveys can bring about cosmological parameters will be presented. I will describe the present and near future constraints coming from current galaxy surveys. I will review also the future projects that are proposed or in construction, and their expected sensitivities, mainly to the dark side of the universe, dark matter and dark energy.
Most information about cosmological parameters and the inflationary universe comes from the CMB, however with the advent of galaxy surveys such as the DES and Euclid further constraints can be obtained from LSS. The gravitational collapse of matter is a complex non-linear process, and is typically modelled numerically with N-body codes. Since N-body codes are expensive to run many have...
Inflation provides a dynamical mechanism to seed density fluctuations that eventually collapse to form all of the structure in the observable universe. However, microphysical theories of inflation often predict that on scales much larger than our present horizon, the universe may be extremely inhomogeneous.
One possible source of such ultra-large scale structure (ULSS) is from the initial...
The Planck data on the CMB power spectrum marginally support pronounced deviations from scale invariance at several multipole ranges. We examine the implications of such features for the scalar bispectrum and the tensor power spectrum providing several concistency relations and templates while highlighting the power of joint analysis of spectra in search for features.
Cosmological correlation functions encode the spectrum of particles during inflation, in analogy to scattering amplitudes in colliders. In this talk, I will discuss the imprints of massive particles with arbitrary spin on cosmological correlators. The spinning case is particularly interesting because the detection of massive higher-spin particles would be strongly indicative of a stringy...
This talk is based on the vacuum energy sequestering scenario which is an approach to tackling cosmological constant problem via global modifications of gravity. We will discuss the core issue with the cosmological constant, namely, radiative instability and show how in the vacuum energy sequestering proposal the loop corrections decouple from the gravitational field equations order by order...
Primordial Black Holes (PBH) arise naturally from high peaks in the curvature power spectrum of near-inflection-point single-field inflation, and could constitute today the dominant component of the dark matter in the universe. In this talk we explore the possibility that a broad spectrum of PBH is formed in models of Critical Higgs Inflation (CHI), where the quasi-inflection point is related...
According to the Standard Model of Cosmology, about 25% of the content of the universe is composed of dark matter. From a theoretical point of view, there are many possible alternatives to explain its origin and composition, ranging from ultralight axions to supermassive black holes. However, despite many experimental efforts, the nature of dark matter is still obscure. One interesting...
We consider formation of primordial black holes (PBHs) in multi-field inflation models ( double inflation or axion curvaton model ) and discuss the possibility that produced PBHs account for the observed gravitational events by LIGO or all dark matter of the universe. We point out that the current pulsar timing array (PTA) experiments already put severe constraints on gravitational waves...
Modified gravity models with screening mechanisms, such as galileons, are prime dark energy candidates but they are notoriously difficult to test. In this talk, I will discuss a new scenario for testing galileons. Black holes do not feel the galileon force and, as a consequence, the supermassive black holes in galaxies falling into clusters should be offset from the galactic centre by a...
Dynamical scanning of the Higgs mass by an axion-like particle during inflation may provide a cosmological component to explaining part of the hierarchy problem. We propose a novel interplay of this cosmological relaxation mechanism with inflation, whereby the backreaction of the Higgs vacuum expectation value near the weak scale causes inflation to end. As Hubble drops, the relaxion's...
We propose a new scenario of cosmological relaxation compatible with reheating temperature higher than the electroweak scale. Cosmological relaxation is a novel solution to the hierarchy problem, which is proposed recently. However, the barrier potential, that settles the relaxion down to realize the correct electroweak scale, vanishes at high temperature where the electroweak symmetry...
Talk shall describe the role of light fields indirectly coupled to background during preheating. In our previous study, when we considered massless background field, we proved that non-perturbative production of states associated with such fields can be sizeable due to quantum corrections. Talk will extend this study considering massive inflaton within the interacting field formalism. It helps...
We propose a phenomenological class of inflationary models in which the assumption of inflaton slow-roll is replaced by more general, constant-roll condition. We derive general exact solution for the inflaton potential and dynamics, and show that there exists parameter region that satisfies the latest observational constraint on the scalar spectral index and the tensor-to-scalar ratio. We...
We analyze two models in which primordial inflation has non-standard features. In the first model we study the evolution of a system in which the inflaton is slowed down by dissipation of energy into gauge bosons instead of the usual Hubble friction: in particular we study the conditions of the onset of such a scenario from a static field configuration, its evolution and we mention some...
A violation of the diffeomorphism (Diff) invariance generically induces an additional degree of freedom. In Horava-Lifshitz (HL) gravity, where the 4D Diff invariance is broken into the foliation preserving Diff, there appears a scalar degree of freedom in the gravity sector, Khronon, which describes the degree of freedom for the time foliation. One may naively expect that during inflation, we...
I will discuss the cosmological consequences of higher-dimensional operators respecting the asymptotic symmetries of the tree-level Higgs inflation action. The main contribution of these operators to the renormalization group enhanced potential is localized in a compact field range, whose upper limit is close to the end of inflation. The spectrum of primordial fluctuations in the so-called...
Scalar fields with non-canonical kinetic terms are ubiquitous in theories of dark energy and modified gravity. This naturally raises the question of how non-perturbative effects, like domain walls and quantum tunneling, are modified in the presence of these kinetic terms. Focusing on galileons, which appear in the decoupling limit of massive gravity and DGP, I will discuss the construction and...
In models of inflation driven by an axion-like pseudoscalar field, the inflaton, a, may be coupled to the standard model hypercharge via a Chern-Simons-type interaction, L ⊃ a F F̃ . This coupling results in explosive gauge field production during inflation, which has two interesting phenomenological consequences: (1) The primordial hypermagnetic field is maximally helical and, thus,...
We show that a detectable tensor-to-scalar ratio (r≥0.001) on the CMB scale can be generated even during extremely low energy inflation which saturates the BBN bound ρ=(30MeV)^4. The source of the gravitational waves is not quantum fluctuations of graviton but those of SU(2) gauge fields, energetically supported by coupled axion fields. The curvature perturbation, the backreaction effect and...
Contrary to popular belief stochastic gravitational waves might exist in reach of aLIGO (in operation by about 2020). I present a scenario, based on a scalar singlet extension of the Standard Model, that generates such gravitational waves.
Primordial black holes (PBHs) are one of the candidates to explain the gravitational wave (GW) signals observed by the LIGO detectors. Among several phenomena in the early Universe, cosmic inflation is a major example to generate PBHs from large primordial density perturbations. In this talk, we discuss the possibility to interpret the observed GW events as mergers of PBHs which are produced...
The study of the renormalization group improved effective potential of the Standard Model has revealed the existence of a local maximum at field strengths of the order of 10^10 GeV. If the Standard Model is valid for very high energy scales, then the possibility of the production of cosmological domain walls in the early Universe occurs.
We investigated the dynamics of networks of domain...
The origin of the matter / antimatter asymmetry is one of the most persistent and challenging problems in the study of the early universe. In this talk I will describe how the baryon asymmetry may have arisen from the decaying helicity of a primordial (hyper-)magnetic field without further need for beyond-the-SM particles or interactions. The relic baryon asymmetry is shown to depend...
