We consider the spatially nonlocal response functions of graphene obtained on the basis of first principles of quantum field theory using the polarization tensor in the areas of both the on- and off-the-mass-shell waves. We show that at zero temperature the longitudinal permittivity of graphene is the regular function, whereas the transverse one possesses a double pole for any nonzero wave vector. According to our results, both the longitudinal and transverse permittivities satisfy the dispersion (Kramers-Kronig) relations connecting their real and imaginary parts, as well as expressing each of these permittivities along the imaginary frequency axis via its imaginary part. For the transverse permittivity, we find the form of an additional term arising in the dispersion relations due to the presence of a double pole. The form of dispersion relations is unaffected by the branch points that arise on the real frequency axis in the presence of spatial nonlocality. We discuss the obtained results in connection with the well-known problem of the Lifshitz theory, which has long been found in conflict with the measurement data when using the much studied response function of metals. A possible way of attack on this problem based on the case of graphene is suggested.

We analyze quantum properties of $\mathcal{N}=2$ and $\mathcal{N}=4$ supersymmetric gauge theories formulated in terms of $\mathcal{N}=1$ superfields and investigate the conditions imposed on a renormalization prescription under which the nonrenormalization theorems are valid. For this purpose in these models we calculate the two-loop contributions to the anomalous dimensions of all chiral matter superfields and the three-loop contributions to the $\beta$-functions for an arbitrary $\mathcal{N}=1$ supersymmetric subtraction scheme supplementing the higher covariant derivative regularization. We demonstrate that, in general, the results do not vanish due to the scheme dependence, which becomes essential in the considered approximations. However, the two-loop anomalous dimensions vanish if a subtraction scheme is compatible with the structure of quantum corrections and does not break the relation between the Yukawa and gauge couplings which follows from $\mathcal{N}=2$ supersymmetry. Nevertheless, even under these conditions the three-loop contribution to the $\beta$-function does not in general vanishes for $\mathcal{N}=2$ supersymmetric theories. To obtain the purely one-loop $\beta$-function, one should also chose an Novikov, Shifman, Vainshtein, and Zakharov (NSVZ) renormalization prescription. The similar statements for the higher loop contributions are proved in all orders.

We investigate particle creation and entanglement structure in a dispersive model with subluminal dispersion relation. Assuming the step function spatial velocity profile of the background flow, mode functions for a massless scalar field are exactly obtained by the matching method. Power spectrums of created particles are calculated for the subsonic and the trans-sonic flow cases. For the trans-sonic case, the sonic horizon exists, and created particles show the Planckian distribution for the low frequency region, but the thermal property disappears for the high frequency region near the cutoff frequency introduced by the nonlinear dispersion. For the subsonic case, although the sonic horizon does not exist, the effective group velocity horizon appears due to the nonlinear dispersion for the high frequency region, and an approximate thermal property of the power spectrum arises. The relation between particle creation and entanglement between each mode is also discussed.

We discuss how a post-inflationary reheating phase characterized by a nonstandard multiple scalar field cosmology can change the thermal history of the Universe, affecting minimal high-scale leptogenesis. In particular, we explore a class of models where a set of scalar fields in a brane-inspired dynamical scenario modifies the Boltzmann equations concerning standard leptogenesis. The produced lepton asymmetry $Y_L$, due to the decays of heavy Majorana right-handed neutrinos responsible for generating Standard Model neutrino masses via the type-I seesaw, is affected as well. In particular, both an enhancement and a reduction of $Y_L$ can be obtained, depending on the values of the (new) involved parameters and on the number of additional scalar fields.

The variational principle is the main approach to obtain complete and self-consistent field equations in gravitational theories. This method works well in pure field cases such as $f(R)$ and Horndeski gravities. However, debates exist in the literature over the modification of a perfect fluid. This paper aims to clarify this issue. For a wide class of modified fluid Lagrangians, we show that the variational principle is unable to give complete field equations. One additional equation is required for completeness. Adopting the local energy conservation equation gives the modified fluid a good thermodynamic interpretation. Our result is the first modified fluid theory that can incorporate energy conservation. As an application of this framework, we propose a specific modified fluid model to realize early dark energy triggered by the cosmic radiation-matter transition. This model naturally explains why early dark energy occurs around matter-radiation equality and is useful in erasing the Hubble tension.

Superradiant instability of rotating black holes (BHs) leads to the formation of a cloud of ultralight bosons, such as axions. When the BH with the cloud belongs to a binary system and is in an inspiraling orbit, the resonant transition between the axion’s bound states can occur. We study the history of the evolution of the binary system accompanying the cloud composed of the fastest growing mode and its impact on the observational signatures, especially for small mass ratio cases. In this case, the hyperfine resonance, which has a very small resonance frequency, is relevant. Therefore, due to the long timescale, we should take into account the decaying process of axions in the transition destination mode, the backreaction to the orbital motion and the central BH, and gravitational emission from the cloud. We present a formulation to examine the evolution of the system around the resonance and useful expressions for the analysis. As a result, we found the mass of the cloud that can remain after the resonance is, at most, about ${10}^{-5}$ of the central BH. The maximum remaining cloud mass is achieved when the mass ratio of the binary is $q\sim {10}^{-3}$. In addition, we show that the resonant transition hardly changes the BH mass and spin distribution, while the associated modification of the gravitational wave frequency evolution when the binary passes through the resonance can be a signature of the presence of the cloud.

The proton synchrotron radiation is considered as the origin of high-energy emission of blazars at times. However, extreme physical parameters are often required. In this work, we propose an analytical method to study the parameter space when applying the proton synchrotron radiation to fit the keV, GeV, and very-high-energy emission of blazar jets. We find that proton synchrotron radiation can fit the high-energy hump when it peaks beyond tens GeV without violating basic observations and theories. For the high-energy hump peaked around GeV band, extreme parameters, such as a super-Eddington jet power and a very strong magnetic field, are required. For the high-energy hump peaked around keV band, if an acceptable parameter space can be found depends on the object’s keV luminosity.

The high-density behavior of nuclear matter is analyzed within a relativistic mean field description with nonlinear meson interactions. To assess the model parameters and their output, a Bayesian inference technique is used. The Bayesian setup is limited only by a few nuclear saturation properties, the neutron star maximum mass larger than $2M_{\odot }$, and the low-density pure neutron matter equation of state (EOS) produced by an accurate ${\mathrm{N}}^3\mathrm{LO}$ calculation in chiral effective field theory. Depending on the strength of the nonlinear scalar vector field contribution, we have found three distinct classes of EOSs, each one correlated to different star properties distributions. If the nonlinear vector field contribution is absent, the gravitational maximum mass and the sound velocity at high densities are the greatest. However, it also gives the smallest speed of sound at densities below three times saturation density. On the other hand, models with the strongest nonlinear vector field contribution predict the largest radii and tidal deformabilities for $1.4M_{\odot }$ stars, together with the smallest mass for the onset of the nucleonic direct Urca processes and the smallest central baryonic densities for the maximum mass configuration. These models have the largest speed of sound below three times saturation density, but the smallest at high densities, in particular, above four times saturation density the speed of sound decreases approaching approximately $\sqrt{0.4}c$ at the center of the maximum mass star. On the contrary, a weak nonlinear vector contribution gives a monotonically increasing speed of sound. A $2.75M_{\odot }$ neutron star (NS) maximum mass was obtained in the tail of the posterior with a weak nonlinear vector field interaction. This indicates that the secondary object in GW190814 could also be an NS. The possible onset of hyperons and the compatibility of the different sets of models with perturbative QCD (pQCD) are discussed. It is shown that pQCD favors models with a large contribution from the nonlinear vector field term or which include hyperons.

Since it has been pointed out that physics beyond the Standard Model may be constrained by gravitational waves from cosmic strings, it has been more important to clarify in what cases cosmic strings are formed. We study the stability of the embedded string which is formed when $SU(N)\times U(1{)}_X$ gauge symmetries are broken to $SU(N-1)\times U(1{)}_Q$, and find that the stability condition can be determined by two mass ratios of the Higgs and massive gauge bosons, and does not explicitly depend on $N$. We also show that the result can be extended in supersymmetric models. In addition, we apply these results to several models and discuss the important feature of the Higgs to produce the embedded string. Although we find it difficult to be satisfied in normal realistic grand unified theory models, it is possible if $SU(N)$ and $U(1{)}_X$ have different origins.

With the accumulation of experimental data, more and more exotic hadrons are observed. Among the interpretations of these exotic hadrons, molecular state and compact multiquark are two of the most popular pictures. However, it is still difficult to determine the structure of an exotic hadron. In this work, we propose a possible way to detect the internal structure of an exotic state. When a molecular state composed of two consistent hadrons is attacked by another particle, one of the constituents should be kicked out while another quasifree constituent stays almost unaffected. It is different from a compact multiquark which has no obvious subcluster. In this work, taking the $X(3872)$ as an example, we perform a Dalitz plot analysis of such reaction to find the effect of the different internal structures. Under the assumption of the $X(3872)$ as a molecular state or a compact tetraquark state, with the help of the effective Lagrangians, the Dalitz plot and the invariant mass spectrum are estimated with different total invariant mass of three final particles, and the effect of different binding energies is also discussed. Obvious event concentration can be observed as strips in the Dalitz plot and sharp peaks in the invariant mass spectrum for the $X(3872)$ with a small binding energy under the molecular state picture, while such concentration cannot be observed under the compact tetraquark picture. Such phenomenon can be applied to identify the internal structure of a new hadron state.

The conventional misalignment mechanism for scalar dark matter depends on the initial field value, which governs the oscillation amplitude and present-day abundance. We discuss a mechanism by which a feeble coupling of dark matter to a fermion in thermal equilibrium drives the scalar toward its high-temperature potential minimum at large field values, dynamically generating misalignment before oscillations begin. Unlike conventional misalignment production, the dark matter abundance is dictated by microphysics and not by initial conditions. As an application of the generic mechanism, we discuss a realistic scenario in which dark matter couples to the muon.

We introduce a strategy to compute EPRL spin foam amplitudes with many internal faces numerically. We work with sl2cfoam-next, the state-of-the-art framework to numerically evaluate spin foam transition amplitudes. We find that uniform sampling Monte Carlo is exceptionally effective in approximating the sum over internal quantum numbers of a spin foam amplitude, considerably reducing the computational resources necessary. We apply it to compute large volume divergences of the theory and find surprising numerical evidence that the EPRL vertex renormalization amplitude is instead finite.

Horndeski gravity is the most general scalar-tensor theory with one scalar field leading to second-order Euler-Lagrange field equations for the metric and scalar field, and it is based on Riemannian geometry. In this paper, we formulate an analog version of Horndeski gravity in a symmetric teleparallel geometry which assumes that both the curvature (general) and torsion are vanishing and gravity is only related to nonmetricity. Our setup requires that the Euler-Lagrange equations for not only metric and scalar field but also connection should be at most second order. We find that the theory can be always recast as a sum of the Riemannian-Horndeski theory and new terms that are purely teleparallel. Due to the nature of nonmetricity, there are many more possible ways of constructing second-order theories of gravity. In this regard, up to some assumptions, we find the most general $k$-essence extension of symmetric teleparallel Horndeski gravity. We also formulate a novel theory containing higher-order derivatives acting on nonmetricity while still respecting the second-order conditions, which can be recast as an extension of kinetic gravity braiding. We finish our study by presenting the FLRW cosmological equations for our model.

A confident discovery of physics beyond what has been consistently modeled from gravitational wave (GW) data requires a technique that can distinguish between noise artifacts and unmodeled signatures while also shedding light on the underlying physics. We propose a new data analysis method, SCoRe (Structured Correlated Residual), to search for unmodeled physics in GW data, which addresses both of these aspects. The method searches for structure in the cross-correlation power spectrum of residual strains of pairs of GW detectors by projecting this power spectrum onto a frequency-dependent template. The template may be model independent or model dependent and is constructed based on the properties of the GW source parameters. The projection of the residual strain enables distinction between noise artifacts and any true signal while capturing possible dependence on the GW source parameters. Our method is constructed within a Bayesian framework, and we demonstrate its application on a model-independent toy example and for a model motivated by an effective field theory of gravity. The method developed here will be useful for searching for a wide variety of new physics and yet-to-be-modeled known physics in GW data accessible from the current network of LIGO-Virgo-KAGRA detectors, as well as from future earth- and space-based GW detectors such as $\mathrm{A}+$, LISA, Cosmic Explorer, and the Einstein Telescope.

The Hamiltonian approach to black hole entropy, recently proposed in the framework of Poincaré gauge theory, is extended by including the scalar matter. The improved approach is used to analyze asymptotic charges and entropy of a typical black hole with scalar hair in two complementary dynamical settings, in GR and in the teleparallel gravity. In both cases, the results confirm the validity of the first law.

Gravitons radiated from light, evaporating black holes contribute to the stochastic background of gravitational waves. The spectrum of such emission depends on both the mass and the spin of the black holes, as well as on the redshifting that occurs between the black hole formation and today. This, in turn, depends on the expansion history of the Universe, which is largely unknown and unconstrained at times prior to the synthesis of light elements. Here, we explore the features of the stochastic background of gravitational waves from black hole evaporation under a broad range of possible early cosmological histories. The resulting gravitational wave signals typically peak at very high frequencies, and offer opportunities for proposed ultrahigh-frequency gravitational wave detectors. Lower-frequency peaks are also possible, albeit with a suppressed intensity that is likely well below the threshold of detectability. We find that the largest intensity peaks correspond to cosmologies dominated by fluids with equations of state that have large pressure-to-density ratios. Such scenarios can be constrained on the basis of violation of $\mathrm{\Delta }{N}_{\mathrm{eff}}$ bounds.

The tomography of the polarized Sunyaev-Zeldvich effect due to free electrons of galaxy clusters can be used to constrain the nature of dark energy because Cosmic Microwave Background quadrupoles at different redshifts as the polarization source are sensitive to the Integrated Sachs-Wolfe effect. Here we show that the low multipoles of the temperature and E-mode polarization anisotropies from the all-sky CMB can improve the constraint further through the correlation between them and the CMB quadrupoles viewed from the galaxy clusters. Using a Monte Carlo simulation, we find that low multipoles of the temperature and E-mode polarization anisotropies potentially improve the constraint on the equation of state of dark energy parameter by about $17$ percent.

The parameter space of massive axionlike particles (ALPs) with $m_a\sim \mathcal{O}(100)\mathrm{MeV}$ and coupled with nucleons is largely unexplored. Here, we present new constraints in this parameter region. In doing so, we characterize the supernova emissivity of heavy ALPs from a protoneutron star, including for the first time mass effects in both nucleon-nucleon Bremsstrahlung and pionic Compton processes. In addition, we highlight novel possibilities to probe the couplings with photons and leptons from supernova ALP decays.

We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is assumed to satisfy ideal magnetohydrodynamic (MHD) conditions, while in the region of negligible mass density the force-free conditions or electromagnetic vacuum are assumed. Solving all components of Einstein’s equations, Maxwell’s equations, ideal MHD equations, and force-free conditions, equilibriums of rotating compact stars associated with mixed poloidal and toroidal magnetic fields are obtained. It is found that in the extreme cases the strong mixed magnetic fields concentrating in a toroidal region near the equatorial surface expel the matter and form a force-free toroidal magnetotunnel. We also introduce a new differential rotation law for computing solutions associated with force-free magnetosphere, and present other extreme models without the magnetotunnel.

We calculate the gravitational-wave (GW) signatures of detailed three-dimensional (3D) core-collapse supernova simulations spanning a range of massive stars. Most of the simulations are carried out to times late enough to capture more than 95% of the total GW emission. We find that the $f/g$-mode and $f$-mode of protoneutron star oscillations carry away most of the GW power. The $f$-mode frequency inexorably rises as the protoneutron star (PNS) core shrinks. We demonstrate that the GW emission is excited mostly by accretion plumes onto the PNS that energize modal oscillations and also high-frequency (“haze”) emission correlated with the phase of violent accretion. The duration of the major phase of emission varies with exploding progenitor, and there is a strong correlation between the total GW energy radiated and the compactness of the progenitor. Moreover, the total GW emissions vary by as much as 3 orders of magnitude from star to star. For black hole formation, the GW signal tapers off slowly and does not manifest the haze seen for the exploding models. For such failed models, we also witness the emergence of a spiral shock motion that modulates the GW emission at a frequency near $\sim 100\mathrm{Hz}$ that slowly increases as the stalled shock sinks. We find significant angular anisotropy of both the high- and low-frequency (memory) GW emissions, though the latter have very little power.