We demonstrate that the recently announced signal for a stochastic gravitational wave background (SGWB) from pulsar timing array (PTA) observations, if attributed to new physics, is compatible with primordial GW production due axion-gauge dynamics during inflation. More specifically we find axion-U(1) models may lead sufficient particle explain while simultaneously source some fraction of sub-solar mass black holes (PBHs) as signature. Moreover there parity violation in sector, hence model...

Abstract The coupling between a pseudo-scalar inflaton and gauge field leads to an amount of additional density perturbations gravitational waves (GWs) that is strongly sensitive the speed. This naturally results in enhanced GWs at (relatively) small scales exited horizon well after CMB ones, can be probed by variety GW observatories (from pulsar timing arrays, astrometry, space-borne ground-based interferometers). production occurs regime which significantly backreacts on motion. Contrary...

We study a variant of the Chromo-Natural Inflation (CNI) mechanism in which inflaton interacts only gravitationally with CNI fields. Integrating out all non-dynamical scalar fields model results coupling between perturbations and pseudo-scalar is significantly greater than one obtained absence gauge dynamics. compute how this impacts power spectrum that are sourced nonlinearly by unstable (tensor) modes, we require amplitude these modes well below linear perturbations. Combining result...

A bstract We study the impact of sphaleron-induced thermal friction on axion dark-matter abundance due to interaction an axion-like particle (ALP) with a dark non-abelian gauge sector in secluded bath. Thermal can either enhance relic density by delaying onset oscillations or suppress it damping them. derive analytical formula for frictional adiabatic invariant , which remains constant along evolution and allows us compute general set-up. Even most minimal scenario, single group is...

Several models of inflation employing a triplet SU(2) vectors with spatially orthogonal vacuum expectation values (VEVs) have been recently proposed. One (tensor) combination t the vector modes is amplified in some momentum range during inflation. Due to VEVs, this mixes gravitational waves (GW) at linear level, resulting GW amplification that has well studied literature. Scalar perturbations class so far only level. We perform first step toward nonlinear computation using as an example...

Motivated by some of the recent swampland conjectures, we study implementation for late time acceleration Universe a mechanism developed Anber and Sorbo in context primordial inflation, which an axion field can slowly roll steep potential due to additional friction provided its coupling U(1) gauge field. We first realization this N = 2 supergravity models resulting from string compactifications on Calabi--Yau manifolds. then transition between matter domination domination, show that indeed...

We study a number of well-motivated theories modified gravity with the common overarching theme that they predict existence compact objects, such as black holes and wormholes endowed scalar hair. compute shadow radius resulting objects demonstrate hole images, M87* or more recent SgrA* by Event Horizon Telescope (EHT) collaboration, could provide powerful way to constrain deviations metric functions from what is expected general relativity (GR) solutions. focus our attention on...

We study an inflation model with a flat scalar potential supported by observations and find that slow-roll can emerge after quasicyclic phase of the Universe, where it undergoes repeated expansions contractions for finite time period. The initial conditions positive spatial curvature required such nontrivial dynamics align quantum creation Universe. key ingredients trigger are dissipative interactions inflaton, which necessary to reheat Universe thus give us observational handle on...

Inflationary models, especially those with plateau-type potentials, are consistent the cosmological data, but inflation itself does not resolve initial singularity. This singularity is resolved, for example, by idea of quantum creation Universe from nothing such as tunneling and no-boundary proposals. The simplest one predicts a closed Universe. Motivated these facts, we investigate classical dynamics universe potential. Depending on inflaton field value, can undergo variety events: an...

Abstract Axion-inflation models are a compelling candidate as mechanism behind the accelerated expansion in early universe light of possibility to embed them higher dimensional UV complete theories and exciting prospect testing with next-generation cosmological probes. Adding an Abelian gauge sector axion-inflation makes for rich, interesting, phenomenology spanning from primordial black holes gravitational waves (GWs). Several recent studies employ approximate analytic (Gaussian) template...

We revisit the no-hair theorems in Einstein-Scalar-Gauss-Bonnet theory with a general coupling function between scalar and Gauss-Bonnet term four dimensional spacetime. first resolve conflict caused from incomplete derivation of old theorem by taking into account surface restore its reliability. also clarify that novel is always evaded for regular black hole solutions without any restrictions as long regularity conditions are satisfied.

We consider the case of axion-like particles (ALPs) during inflation. When coupled to a non-Abelian gauge sector via Chern-Simons term, ALPs support an intriguing, testable, phenomenology with very distinctive features including chiral primordial gravitational waves. For sufficiently small values vev and coupling, scalar perturbations in exhibit known instability. harness power such instability for black hole (PBH) generation. In axion-inflaton, one is dynamically driven into...

We demonstrate that the recently announced signal for a stochastic gravitational wave background (SGWB) from pulsar timing array (PTA) observations, if attributed to new physics, is compatible with primordial GW production due axion-gauge dynamics during inflation. More specifically we find axion-$U(1)$ models may lead sufficient particle explain while simultaneously source some fraction of sub-solar mass black holes (PBHs) as signature. Moreover there parity violation in sector, hence model...

We compute the gravitational leptogenesis generated from parity-violating waves sourced by an abelian gauge field coupled to a pseudo-scalar inflation. show that, once CMB bound on tensor-to-scalar ratio is enforced, lepton asymmetry produced this mechanism during inflation too small account for observed baryon of universe, irrespectively inflaton potential, strength its coupling field, and details reheating.

The coupling between a pseudo-scalar inflaton and gauge field leads to an amount of additional density perturbations gravitational waves (GWs) that is strongly sensitive the speed. This naturally results in enhanced GWs at (relatively) small scales exited horizon well after CMB ones, can be probed by variety GW observatories (from pulsar timing arrays, astrometry, space-borne ground-based interferometers). production occurs regime which significantly backreacts on motion. Contrary earlier...

We study the impact of gravitational wave memory on distribution far away light sources in sky. For first time, we compute buildup small, but permanent tensor distortions metric over cosmological timescales using realistic models compact binary coalescences whose rate occurrence is extrapolated at $z\ensuremath{\sim}\mathcal{O}(1)$. This allows for a consistent computation random-walk-like evolution which, turn, used to estimate overall shape and magnitude astrometric deflections light. find...

We study the impact of gravitational wave memory on distribution far away light sources in sky. For first time we compute built up small, but permanent tensor distortions metric over cosmological time-scales using realistic models compact binary coalescences (CBCs) whose rate occurrence is extrapolated at $z\sim {\cal O}(1)$. This allows for a consistent computation random-walk like evolution which, turn, used to estimate overall shape and magnitude astrometric deflections light. find that...

Axion-inflation models are a compelling candidate as mechanism behind the accelerated expansion in early universe light of possibility to embed them higher dimensional UV complete theories and exciting prospect testing with next-generation cosmological probes. Adding an Abelian gauge sector axion-inflation makes for rich, interesting, phenomenology spanning from primordial black holes gravitational waves (GWs). Several recent studies employ approximate analytic (Gaussian) template...

Inflationary models, especially those with plateau-type potentials, are consistent the cosmological data, but inflation itself does not resolve initial singularity. This singularity is resolved, for example, by idea of quantum creation Universe from nothing such as tunneling and no-boundary proposals. The simplest one predicts a closed Universe. Motivated these facts, we investigate classical dynamics universe potential. Depending on inflaton field value, can undergo variety events: an...

We study an inflation model with a flat scalar potential supported by observations and find that slow-roll can emerge after quasi-cyclic phase of the Universe, where it undergoes repeated expansions contractions for finite time period. The initial conditions positive spatial curvature required such nontrivial dynamics align quantum creation Universe. key ingredients trigger are dissipative interactions inflaton, which necessary to reheat Universe thus give us observational handle on...

We revisit the no-hair theorems in Einstein-Scalar-Gauss-Bonnet theory with a general coupling function between scalar and Gauss-Bonnet term four dimensional spacetime. In case of old theorem surface has so far been ignored, but this plays crucial role when does not vanish at infinity field admits power expansion respect to inverse radial coordinate that regime. also clarify novel is always evaded for regular black hole solutions without any restrictions as long regularity conditions are satisfied.

We study a number of well-motivated theories modified gravity with the common overarching theme that they predict existence compact objects such as black holes and wormholes endowed scalar hair. compute shadow radius resulting demonstrate hole images M87$^*$ or more recent SgrA$^*$ by Einstein Horizon Telescope (EHT) collaboration may provide powerful way to constrain deviations metric functions from what is expected general relativity (GR) solutions. focus our attention on...

We use a large set of halo mass function (HMF) models in order to investigate their ability represent the observational Cluster Mass Function (CMF), derived from $\mathtt{GalWCat19}$ cluster catalogue, within $\Lambda$CDM cosmology. apply $\chi^2$ minimization procedure constrain free parameters models, namely $\Omega_m$ and $\sigma_8$. find that all HMF fit well CMF, while Bocquet et. al. model provides best fit, with lowest value. Utilizing {\em Index Inconsistency} (IOI) measure, we...