Thermal effects from the ensemble average and thermal mass are analyzed in the model of axionic inflaton interacting with U(1) gauge fields through the Chern-Simons coupling $\propto \varphi F_{\mu \nu }{\tilde{F}}^{\mu \nu }/f$ under equilibrium. The ensemble average eliminates the divergence of radiational spectral density. The cosmic temperature is controlled by the parameter $\xi =\dot{\varphi }/(2Hf)$ and the renormalization coefficient ${\alpha }_T$. It is found that the adiabatic approximation is always corresponding to a slow-roll approximation in the (quasi–)de Sitter universe. The equilibrium condition and backreaction constrain the parameter in a range of $2.47<\xi <6.52$, and the axion becomes thermalized if $\xi \simeq 4.0$. Thermal mass leads to the correlation of scalar perturbation and tensor perturbation, which may be a potential method to distinguish different cosmological models. In addition, the tensor-to-scalar ratio is suppressed in a form proportional to $H/T$ if the fields become thermal in the Standard Model. On the other hand, the condition $\xi <3.0$ is the same as cold inflation, i.e., $r\simeq 16ϵ$, although thermal effects are taken into consideration.

Extracting the cosmic microwave background (CMB) blackbody temperature power spectrum—which is dominated by the primary CMB signal and the kinematic Sunyaev-Zel’dovich (kSZ) effect—from millimeter-wave sky maps requires cleaning other sky components. In this work, we develop new methods to use large-scale structure (LSS) tracers to remove cosmic infrared background (CIB) and thermal Sunyaev-Zel’dovich (tSZ) contamination in such measurements. Our methods rely on the fact that LSS tracers are correlated with the CIB and tSZ signals, but their two-point correlations with the CMB and kSZ signals vanish on small scales, thus leaving the CMB blackbody power spectrum unbiased after cleaning. We develop methods analogous to delensing [de-CIB or de-($\mathrm{CIB}+\mathrm{tSZ}$)] to clean CIB and tSZ contaminants using these tracers. We compare these methods to internal linear combination (ILC) methods, including novel approaches that incorporate the tracer maps in the ILC procedure itself, without requiring exact assumptions about the CIB spectral energy distribution. As a concrete example, we use the unWISE galaxy samples as tracers. We provide calculations for a combined Simons Observatory and Planck-like experiment, with our simulated sky model comprising eight frequencies from 93 to 353 GHz. Using unWISE tracers, improvements with our methods over current approaches are already non-negligible: we find improvements up to 20% in the kSZ power spectrum signal-to-noise ratio (SNR) when applying the de-CIB method to a tSZ-deprojected ILC map. These gains could be more significant when using additional LSS tracers from current surveys and will become even larger with future LSS surveys, with improvements in the kSZ power spectrum SNR up to 50%. For the total CMB blackbody power spectrum, these improvements stand at 4% and 7%, respectively.

We study the effect of temperature on the global properties of static and slowly rotating self-gravitating Bose-Einstein condensate (BEC) stars within general relativity. We employ a recently developed temperature-dependent BEC equation of state (EOS) to describe the stellar matter by assuming that the condensate can be described by a nonrelativistic EOS. Stellar profiles are obtained using general relativistic Hartle-Thorne slow rotation approximation equations. We find that with increasing temperatures mass-radius values are found to be decreasing for the static and rotating cases, though the presence of temperature supports high mass values at lower central densities. Countering effects of rotation and temperature on the BEC stellar structure are analyzed and quantified. We report that the inclusion of temperature has a significant effect on the rotating stellar profiles but a negligible effect on the maximum mass, as in the case of a static system. We also study the effect of EOS parameters—boson mass and strength of the self-interaction on global properties of static and rotating BEC stars—in the presence of temperature.

The evidence of the nano-Hertz stochastic gravitational wave (GW) background is reported by multiple pulsar timing array collaborations. While a prominent candidate of the origin is astrophysical from supermassive black hole binaries, alternative models involving GWs induced by primordial curvature perturbations can explain the inferred GW spectrum. Serendipitously, the nano-Hertz range coincides with the Hubble scale during the cosmological quantum chromodynamics (QCD) phase transition. The influence of the QCD phase transition can modify the spectrum of induced GWs within the nano-Hertz frequency range, necessitating careful analysis. We estimate GWs induced by power-law power spectra of primordial curvature perturbations taking account of the QCD phase transition. Then we translate the implication of the NANOGrav data into the constraint on the power spectrum of the primordial curvature perturbation, which suggests one would underestimate the amplitude by about 25% and the spectral index by up to 10% if neglecting the QCD effect.

We show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent nonstandard postinflationary cosmology make blue-tilted inflationary gravitational waves (GWs) compatible with the recent findings of nanohertz stochastic GW background by the pulsar-timing arrays (PTAs) for high reheating temperatures. The right-handed neutrino (RHN) mass scale has to be $\mathcal{O}(\mathrm{GeV})$. Remarkably, such a scenario produces a correlated signature testable by the future LIGO run. In addition to contributing to the active neutrino masses, $\mathcal{O}(\mathrm{GeV})$ RHNs generate baryon asymmetry of the Universe via low scale leptogenesis. They can be searched for in collider experiments. Therefore, the recent detection by PTAs is not only exciting for GWs in the nanohertz range, it paves the way to test and constrain well-studied mechanisms, such as seesaws, with a low frequency and a correlated measurement of high-frequency GW spectral features, complementary to particle physics searches.

We show that an infinitesimal step of gradient flow can be used for defining a novel approach for computing gradients of physical observables with respect to action parameters. Compared to the commonly used perturbative expansion, this approach does not require calculating any disconnected contribution or vacuum expectation value and can provide results up to 3 orders of magnitudes more precise. On the other hand, it requires a nontrivial condition to be satisfied by the flow action, the calculation of its force and its Laplacian, and the force of the observable, whose gradient needs to be measured. As a proof of concept, we measure gradients in $\beta$ of Wilson loops in a four-dimensional SU(3) Yang-Mills theory simulated on a ${16}^4$ lattice using the Wilson action.

We obtain a quiver representation for a family of knots called double twist knots $K(p,-m)$. Mainly, we exploit the reverse engineering of Melvin-Morton-Rozansky formalism to deduce the pattern of the matrix for these quivers.

We study the conformal bootstrap of 1D CFTs on the straight Maldacena–Wilson line in 4D $\mathcal{N}=4$ super-Yang–Mills theory. We introduce an improved truncation scheme with an “OPE tail” approximation and use it to reproduce the “bootstrability” results of Cavaglià et al. for the OPE-coefficients squared of the first three unprotected operators. For example, for the first OPE-coefficient squared at ’t Hooft coupling $(4\pi {)}^2$, linear-functional methods with two sum rules from integrated correlators give the rigorous result $0.294014873\pm 4.88\times {10}^{-8}$, whereas our methods give with machine-precision computations $0.294014228\pm 6.77\times {10}^{-7}$. For our numerical searches, we benchmark the reinforcement learning soft actor-critic algorithm against an interior point method algorithm (IPOPT) and comment on the merits of each algorithm.

We study the nonconservation of the chiral charge of Dirac fields between past and future null infinity due to the Adler-Bell-Jackiw chiral anomaly. In previous investigations [A. del Rio, Phys. Rev. D 104, 065012 (2021)], we found that this charge fails to be conserved if electromagnetic sources in the bulk emit circularly polarized radiation. In this article, we unravel yet another contribution coming from the nonzero, infrared “soft” charges of the external, electromagnetic field. This new contribution can be interpreted as another manifestation of the ordinary memory effect produced by transitions between different infrared sectors of Maxwell theory, but now on test quantum fields rather than on test classical particles. In other words, a flux of electromagnetic waves can leave a memory on quantum fermion states in the form of a permanent, net helicity. We elaborate this idea in both $1+1$ and $3+1$ dimensions. We also show that, in sharp contrast, gravitational infrared charges do not contribute to the fermion chiral anomaly.

We investigate the accretion disk for a sort of regular black holes which are characterized by sub-Planckian curvature and Minkowskian core. We derive null geodesics outside the horizon of such regular black holes and analyze the feature of the light rays from the accretion disk which can be classified into direct emission, lensed rings, and photon rings. We find that the observed brightness under different emission models is mainly determined by direct emission, while the contribution from the flux of the lensed and photon rings is limited. By comparing with Bardeen black hole with a dS core, it is found that the black hole with a Minkowskian core exhibits distinct astronomical optical features when surrounded by accretion disk, which potentially provides a way to distinguish these two sorts of black holes by astronomical observation.

We compute the scattering angle $\chi$ for hyperboliclike encounters in massless scalar-tensor theories up to third post-Newtonian order for the conservative part of the dynamics. To calculate the gauge-invariant scattering angle as a function of energy and orbital angular momentum, we use the approach of effective-one-body formalism as introduced in Bini and Damour [Phys. Rev. D 96, 064021 (2017)]. We then compute the nonlocal-in-time contribution to the scattering angle by using the strategy of order reduction of nonlocal dynamics introduced for small-eccentricity orbits.

We determine hidden conformal symmetries behind the evolution equations of black hole perturbations in a vector-tensor theory of gravity. Such hidden symmetries are valid everywhere in the exterior region of a spherically symmetric, asymptotically flat black hole geometry. They allow us to factorize second order operators controlling the black hole perturbations into a product of two commuting first order operators. As a consequence, we are able to analytically determine the most general time-dependent solutions for the black hole perturbation equations. We focus on solutions belonging to a highest weight representation of a conformal symmetry, showing that they correspond to quasibound states with an ingoing behavior into the black hole horizon, and exponential decay at spatial infinity. Their time dependence is characterized by purely imaginary frequencies, with imaginary parts separated by integer numbers, as the overtones of quasinormal modes in general relativity.

Strong evidence of the existence of the stochastic gravitational wave background (SGWB) has been reported recently by the North American Nanohertz Observatory for Gravitational Waves, the Parkes Pulsar Timing Array, the European Pulsar Timing Array, and the Chinese Pulsar Timing Array Collaborations. The Bayesian posteriors of the SGWB amplitude and spectrum are compatible with astrophysical predictions for the SGWB from a population of supermassive black hole binaries (SMBHBs). We discuss the modifications arising from the extra scalar or vector radiation to the characteristic dimensionless strain of gravitational waves from SMBHBs and explore the possibility of detecting charges carried by supermassive black holes in modified gravity. The Bayesian posteriors on the tensor amplitude and the spectral exponent of SGWB are ${\log }_{10}{A}_T=-14.64_{-0.27}^{+0.19}$ and $\alpha =-0.35_{-0.25}^{+0.23}$, and a rough upper limit ${\log }_{10}{A}_{V,S}\le -15.2$ is obtained for the SGWB scalar or vector amplitude. The Bayesian factor between the models with and without charge is only 0.6, so the current PTA data do not favor charged SMBHBs over neutral SMBHBs.

We present the exact time-dependent solutions on inhomogeneous spherically symmetric space-time in the conformal invariant Weyl gravity. For this purpose, the subclass of the Lemaître-Tolman metric which is supported by an anisotropic fluid is used. For the first time, the exact solutions of the dynamical equations are obtained for two special cases. One of the exact solutions is a de Sitter space-time and other solution is a class of time-dependent wormhole geometries which can be supported by exotic matter similar to the general relativistic solutions.

We investigate reheating in the string-theory-motivated Kähler moduli inflation I potential, coupled to a light scalar field $\chi$ and produce constraints and forecasts based on cosmic microwave background and gravitational wave observables. We implement a Markov chain Monte Carlo sampling method to compute the adopted model’s parameter ranges allowed by the current cosmic microwave background observations. Floquet analysis and numerical lattice simulations are performed to analyze the nonlinear effects of the model’s (p)reheating phase. We derive bounds on the $\mathrm{\Lambda }$-cold dark matter parameters $A_s$, $n_s$, $n_{\mathrm{run}}$, and $r$ based on Planck results, finding that correlations between model parameters severely constrain the range of these parameters allowed within this model. While the Kähler moduli inflation I potential’s nonvanishing minimum may provide a possible source for the observed dark energy density ${\rho }_{\mathrm{DE}}$ this cannot be tested with current observations. We estimate the 95% CI bounds on the inflaton mass $m_{\varphi }$ and reheating temperature $T_{\mathrm{reh}}$ to be $2.1\times {10}^{13}\mathrm{GeV}\lesssim m_{\varphi }\lesssim 3.2\times {10}^{13}\mathrm{GeV}$ and $T_{\mathrm{reh}}\gtrsim 1.8\times {10}^3\mathrm{GeV}$, respectively. We observe both self-resonance and parametric resonance instability band structures in our Floquet analysis results. Finally, we do not observe any formation of oscillon configurations in our lattice simulations; however, our results predict a stochastic gravitational wave background generated during preheating that would be observable today in the ${10}^9–{10}^{11}\mathrm{Hz}$ frequency range.

We show that the present-day dark matter abundance can be produced through a novel mechanism that involves a very rapid thermal freeze-out caused by inhomogeneous heating and successive fast cooling of small fireballs in the early Universe. The fireballs can be produced from energy deposited in small scale structure growth induced by Yukawa interactions in certain particle species. Yukawa interactions are known to cause growth of halos even during a radiation dominated era, and the same interactions facilitate cooling and collapse of the halos by the emission of scalars. Energy deposited in the Standard Model plasma at the locations of the halo collapse can heat the plasma, re-establishing thermal equilibrium. The subsequent expansion and cooling of plasma fireballs leads to freeze-out of dark matter on timescales much shorter than the Hubble time. This mechanism can produce the right abundance of dark matter for masses and annihilation cross sections previously thought to be ruled out.

We construct a single-field model of inflation that achieves remarkable agreement with Planck and BICEP/Keck cosmological observations. The model, via the presence of an ultraslow-roll phase, generates a sizable scalar-induced gravitational wave (GW) signal at nHz frequencies. We elucidate the distinctive features of this signal concerning its connection to the recent measurement of the low-frequency GW background reported by the NANOGrav collaboration.

We develop semiclassical methods for studying bubble nucleation in models with parameters that vary slowly in time. Introducing a more general rotation of the time contour allows access to a larger set of final states, and typically a non-Euclidean rotation is necessary in order to find the most relevant tunneling solution. We work primarily with effective quantum mechanical models parametrizing tunneling along restricted trajectories in field theories, which are sufficient, for example, to study thin wall bubble nucleation. We also give one example of an exact instanton solution in a particular Kaluza-Klein cosmology where the circumference of the internal circle is changing in time.

The interaction between the quantum vacuum and time-dependent boundaries can produce particles via the dynamical Casimir effect. It is known that, for asymmetric Casimir systems, there is an imbalance in the particle production on either side of the boundary. Here, we consider a real massless scalar field in ($1+1$) dimensions interacting with a moving $\delta -{\delta }^{\prime }$ mirror with time-dependent properties. The spectral distribution and particle creation rate are computed, which now include an additional interference term that can affect different parts of the spectrum in a constructive or destructive manner. The asymmetry of the system is investigated by analyzing the difference in particle spectra produced on the two sides of the mirror. Additionally, we also explore enhancement of the spectrum and its asymmetry within the context of a stationary $\delta -{\delta }^{\prime }$ mirror subject to multiple fluctuation sources.

We carry out a detailed study of the three-point fermion-photon interaction vertex at one-loop order for massive fermions in reduced quantum electrodynamics. This calculation is carried out in arbitrary covariant gauges and space-time dimensions within a recently proposed innovative approach based upon an efficient combination of the first- and second-order formalisms of quantum electrodynamics. This procedure provides a natural decomposition of the vertex into its components which are longitudinal and transverse to the photon momentum. It also separates the spin and scalar degrees of freedom of a fermion interacting electromagnetically, allowing us to readily establish the gauge independence of the Pauli form factor and compute it in an expeditious manner. All incoming and outgoing momenta are taken off shell at the outset. However, we present results for cases of particular kinematic interest whenever required. For the sake of completeness, we also provide expressions for the massive fermion self-energy and photon vacuum polarization, verifying known expressions for massless reduced quantum electrodynamics and computing the renormalization constants ${\mathcal{Z}}_1$, ${\mathcal{Z}}_2$ and ${\mathcal{Z}}_3$. As we provide general expressions for the computed Green functions, we readily reproduce and confirm the results for standard quantum electrodynamics. Comparing the two cases, we infer that the Pauli form factor for reduced quantum electrodynamics is $8/3$ times that for the standard QED in four dimensions, implying a higher Landé $g$-factor. We expect our perturbative calculation of the fermion-photon vertex to serve as a guide for any nonperturbative construction of this Green function, invariably required in the Schwinger-Dyson equation studies of the subject. We also comment on the Landau-Khalatnikov-Fradkin transformations of the massive fermion propagator and provide a comparison with its one-loop calculation.