We propose a more general version of the trans-Planckian censorship conjecture (TCC) which can apply to models of inflation with a varying speed of sound. We find that inflation models with $c_S<1$ are, in general, more strongly constrained by censorship of trans-Planckian modes than canonical inflation models, with the upper bound on the tensor-to-scalar ratio reduced by as much as 3 orders of magnitude for sound speeds consistent with bounds from data. In particular, models which satisfy the TCC, and, therefore, the de Sitter swampland conjecture, can still violate the more general condition for nonclassicality of trans-Planckian modes. As a concrete example, we apply the constraint to Dirac-Born-Infeld inflation models motivated by string theory.

We study in detail the Earth matter effects on the boron neutrinos from the Sun using recently developed 3D models of the Earth. The models have a number of new features of the density profiles, in particular, a substantial deviation from spherical symmetry. In this connection, we further elaborate on relevant aspects of oscillations (${\epsilon }^2$ corrections, adiabaticity violation, entanglement, etc.) and the attenuation effect. The night excesses of the $\nu e-$ and $\nu N-$ events and the day-night asymmetries, $A_{ND}$, are presented in terms of the matter potential and the generalized energy resolution functions. The energy dependences of the cross section and the flux improve the resolution, and consequently, sensitivity to remote structures of the profiles. The nadir angle ($\eta$) dependences of $A_{ND}$ are computed for future detectors DUNE, THEIA, Hyper-Kamiokande, and MICA at the South pole. Perspectives of the oscillation tomography of the Earth with the boron neutrinos are discussed. Next-generation detectors will establish the integrated day-night asymmetry with high confidence level. They can give some indications of the $\eta -$ dependence of the effect, but will discriminate among different models at most at the $(1-2)\sigma$ level. For high-level discrimination, the MICA-scale experiments are needed. MICA can detect the ice-soil borders and perform unique tomography of Antarctica.

We describe charge-neutral neutron star matter in $\beta$-equilibrium using hybrid equations of state (EOSs), where a first-order phase transition from hadronic to quark matter is realized. The hadronic matter is described in a model-independent way by a Taylor expansion around saturation density $n_0$, while the three-flavor Nambu–Jona-Lasinio (NJL) model is used for the quark matter. Exploring the present uncertainty on the empirical parameters of nuclear matter and the parameter space of the NJL model, we construct two data sets of thermodynamically consistent and causal hybrid EOSs, compatible with astrophysical observations. We conclude that, to sustain a considerable quark core size, the intensity of the phase transition from hadron to quark matter cannot be strong, having an energy density gap below $200\mathrm{MeV}/{\mathrm{fm}}^3$, and must occur at baryon densities not above 4 times the saturation density. A nonzero but not too strong quark vector-isoscalar term and a weak vector isovector quark term are required. Large quark cores carrying almost half of the star mass are possible inside neutron stars with a maximum mass $\approx 2.2M_{\odot }$. To get a considerable number of hybrid EOSs predicting quark matter already inside neutron stars with a mass $\sim 1.4M_{\odot }$, we require that the onset of quarks occurs in the range $1.3n_0$ and $2.5n_0$. Neutron stars with large quark cores corresponding to more than one fourth of the total star mass are possible if the energy density gap and the pressure at transition are below $100\mathrm{MeV}/{\mathrm{fm}}^3$. However, under these constraints, the maximum neutron star mass is limited to $\lesssim 2.06M_{\odot }$. No strong signatures from quark matter were found on the radius and the tidal deformability for neutron star masses below $1.8M_{\odot }$.

Discontinuity gravity modes may arise in perturbed quark-hadron hybrid stars when a sharp density jump exists in the stellar interior, and they are a potential fingerprint to infer the existence of quark matter cores in compact objects. When a hybrid star is perturbed, conversion reactions may occur at the quark-hadron interface and may have a key role in global stellar properties such as the dynamic stability and the quasinormal mode spectrum. In this work we study the role of the conversion rate at the interface. To this end, we first derive the junction conditions that hold at the sharp interface of a nonradially perturbed hybrid star in the case of slow and rapid conversions. Then, we analyze the discontinuity $g$-mode in both cases. For rapid conversions, the discontinuity $g$-mode has zero frequency because a displaced fluid element near the phase splitting surface almost immediately adjusts its composition to its surroundings, and gravity cannot provide a buoyancy force. For slow conversions, a $g$-mode exists, and its properties are analyzed here using modern hadronic and quark equations of state. Moreover, it has been shown recently that in the case of slow conversions an extended branch of stable hybrid configurations arises for which $\partial M/\partial {\epsilon }_c<0$. We show that $g$-modes of the standard branch (that is, the one with $\partial M/\partial {\epsilon }_c>0$) have frequencies and damping times in agreement with previous results in the literature. However, $g$-modes of the extended branch have significantly larger frequencies (in the range 1–2 kHz) and much shorter damping times (a few seconds in some cases). We discuss the detectability of $g$-mode GWs with present and planned GW observatories.

The behavior of ${\pi }^0$ meson properties in the presence of a uniform external magnetic field is studied in the context of a nonlocal extension of the Polyakov-Nambu-Jona-Lasinio model. The analysis includes the ${\pi }^0$ mass, the effective ${\pi }^0$-quark coupling and the pion-to-vacuum hadronic form factors, both at zero and finite temperature. Numerical results are compared with previous calculations carried out within the local NJL model, when available. The validity of chiral relations and the features of deconfinement and chiral symmetry restoration transitions are discussed.

A violation of mirror symmetry in the $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$ Dalitz plot has long been recognized as a signal of $C$ and $CP$ violation. Here we show how the isospin of the underlying $C$- and $CP$-violating structures can be reconstructed from their kinematic representation in the Dalitz plot. Our analysis of the most recent experimental data reveals, for the first time, that the $C$- and $CP$-violating amplitude with total isospin $I=2$ is much more severely suppressed than that with total isospin $I=0$.

Recent precise measurement of the electron anomalous magnetic moment (AMM) adds to the longstanding tension of the muon AMM and together strongly point toward physics beyond the Standard Model (BSM). In this work, we propose a solution to both anomalies in an economical fashion via a light scalar that emerges from a second Higgs doublet and resides in the $\mathcal{O}(10)\text{−}\mathrm{MeV}$ to $\mathcal{O}(1)\text{−}\mathrm{GeV}$ mass range yielding the right sizes and signs for these deviations due to one-loop and two-loop dominance for the muon and the electron, respectively. A scalar of this type is subject to a number of various experimental constraints, however, as we show, it can remain sufficiently light by evading all experimental bounds and has the great potential to be discovered in the near-future low-energy experiments. The analysis provided here is equally applicable to any BSM scenario for which a light scalar is allowed to have sizable flavor-diagonal couplings to the charged leptons. In addition to the light scalar, our theory predicts the existence of a nearly degenerate charged scalar and a pseudoscalar, which have masses of the order of the electroweak scale. We analyze possible ways to probe new-physics signals at colliders and find that this scenario can be tested at the LHC by looking at the novel process $pp\to H^{\pm }{H}^{\pm }jj\to l^{\pm }{l}^{\pm }jj+{\cancel{E}}_T$ via same-sign pair production of charged Higgs bosons.

Freeze-in mechanism provides robust dark matter production in the early Universe. Because of its feeble interactions, freeze-in dark matter leaves signals at colliders which are often involved with long-lived particle decays and consequent displaced vertices (DV). In this paper, we develop a method to read off mass spectrum of particles being involved in the DV events at the LHC. We demonstrate that our method neatly works under limited statistics, detector resolution, and smearing effects. The signature of DV at the LHC can come from either highly suppressed phase space or a feeble coupling of particle decay processes. By measuring invisible particle mass spectrum, one can discriminate these two cases and thus extract information of dominant freeze-in processes in the early Universe at the LHC.

While the partition function for QCD in a magnetic field $H$ has been calculated before within chiral perturbation theory up to two-loop order, our investigation relies on an alternative representation for the Bose functions which allows for a clear-cut expansion of thermodynamic quantities in the chiral limit. We first focus on the pion-pion interaction in the pressure and show that—depending on magnetic field strength, temperature, and pion mass—it may be attractive or repulsive. We then analyze the thermodynamic properties in the chiral limit and provide explicit two-loop representations for the pressure in the weak magnetic field limit $|qH|\ll T^2$.

We extend our general framework for semileptonic decay, originally introduced in N. Penalva et al. [Phys. Rev. D 100, 113007 (2019)], with the addition of new physics (NP) tensor terms. In this way, all the NP effective Hamiltonians that are considered in lepton flavor universality violation (LFUV) studies have now been included. Those are left and right vector and scalar NP Hamiltonians and the NP tensor one. Besides, we now also give general expressions that allow for complex Wilson coefficients. The scheme developed is totally general and it can be applied to any charged current semileptonic decay, involving any quark flavors or initial and final hadron states. We show that all the hadronic input, including NP effects, can be parametrized in terms of 16 Lorentz scalar structure functions, constructed out of the NP complex Wilson coefficients and the genuine hadronic responses, with the latter determined by the matrix elements of the involved hadron operators. In the second part of this work, we use this formalism to obtain the complete NP effects in the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau {\overline{\nu }}_{\tau }$ semileptonic decay, where LFUV, if finally confirmed, is also expected to be seen. We stress the relevance of the center of mass (CM) $d^2\mathrm{\Gamma }/(d\omega d\cos {\theta }_{\ell })$ and laboratory (LAB) $d^2\mathrm{\Gamma }/(d\omega d{E}_{\ell })$ differential decay widths, with $\omega$ the product of the hadron four-velocities, ${\theta }_{\ell }$ the angle made by the three-momenta of the charged lepton and the final hadron in the $W^{-}$ CM frame and $E_{\ell }$ the charged lepton energy in the decaying hadron rest frame. While models with very different strengths in the NP terms give the same differential $d\mathrm{\Gamma }/d\omega$ and total decay widths for this decay, they predict very different numerical results for some of the $\cos {\theta }_{\ell }$ and $E_{\ell }$ coefficient-functions that determine the above two distributions. Thus, the combined analysis of the CM $d^2\mathrm{\Gamma }/(d\omega d\cos {\theta }_{\ell })$ and LAB $d^2\mathrm{\Gamma }/(d\omega d{E}_{\ell })$ differential decay widths will help clarifying what kind of NP is a better candidate in order to explain LFUV.

Explicit boundary conditions are given at spatial infinity for four-dimensional supergravity, which provide a realization of the super-Bondi-Metzner-Sachs (BMS) algebra of Awada, Gibbons and Shaw. The results are then generalized to the $N$-extended super-BMS algebras.

We analyze some features of the entanglement entropy for an integer quantum Hall state ($\nu =1$) in comparison with ideas from relativistic field theory and noncommutative geometry. The spectrum of the modular operator, for a restricted class of states, is shown to be similar to the case of field theory or a type ${\mathrm{III}}_1$ von Neumann algebra. We present arguments that the main part of the dependence of the entanglement entropy on background fields and geometric data such as the spin connection is given by a generalized Chern-Simons form. Implications of this result for bringing together ideas of noncommutative geometry, entropy and gravity are briefly commented upon.

We investigate vacuum entanglement harvesting in the presence of a zero mode. We show that, for a variety of detector models and couplings (namely, Unruh-DeWitt qubit and harmonic oscillator detectors, amplitude and derivative coupling), the results are strongly dependent on the state of the zero mode, revealing an ambiguity in studies of entanglement harvesting with Neumann or periodic boundary conditions, or in general in spacetimes with toroidal topologies.

Accurate gravitational-wave (GW) signal models exist for black hole binary (BBH) and neutron-star binary (BNS) systems, which are consistent with all of the published GW observations to date. Detections of a third class of compact-binary systems, neutron-star black hole (NSBH) binaries, have not yet been confirmed, but are eagerly awaited in the near future. For NSBH systems, GW models do not exist across the viable parameter space of signals. In this work we present the frequency-domain phenomenological model, phenomnsbh, for GWs produced by NSBH systems with mass ratios from equal-mass up to 15, spin on the black hole (BH) up to a dimensionless spin of $|\chi |=0.5$, and tidal deformabilities ranging from 0 (the BBH limit) to 5000. We extend previous work on a phenomenological amplitude model for NSBH systems to produce an amplitude model that is parametrized by a single tidal deformability parameter. This amplitude model is combined with an analytic phase model describing tidal corrections. The resulting approximant is compared to publicly available NSBH numerical-relativity simulations and hybrid waveforms constructed from numerical-relativity simulations and tidal inspiral approximants. For most signals observed by second-generation ground-based detectors, it will be difficult to use the GW signal alone to distinguish single NSBH systems from either BNSs or BBHs, and therefore to unambiguously identify an NSBH system.

The purpose of this paper is twofold. First, we introduce a geometric approach to study the circular orbit of a particle in static and spherically symmetric spacetime based on Jacobi metric. Second, we apply the circular orbit to study the weak gravitational deflection of null and timelike particles based on Gauss-Bonnet theorem. By this way, we obtain an expression of deflection angle and extend the study of deflection angle to asymptotically nonflat black hole spacetimes. Some black holes as lens are considered such as a static and spherically symmetric black hole in the conformal Weyl gravity and a Schwarzschild-like black hole in bumblebee gravity. Our results are consistent with the previous literature. In particular, we find that the connection between Gaussian curvature and the radius of a circular orbit greatly simplifies the calculation.

In this work, we consider the full Horndeski Lagrangian applied to wormhole geometries and present the full gravitational field equations. We analyze the general constraints imposed by the flaring-out conditions at the wormhole throat and consider a plethora of specific subclasses of the Horndeski Lagrangian, namely, quintessence and phantom fields, $k$-essence, scalar-tensor theories, covariant Galileons, nonminimal kinetic coupling, kinetic gravity braiding, and the scalar-tensor representation of Gauss-Bonnet couplings, among others. The generic constraints analyzed in this work serve as a consistency check of the main solutions obtained in the literature and draw out new avenues of research in considering applications of specific subclasses of the Horndeski theory to wormhole physics.

We discuss the footprint of evaporation of primordial black holes (PBHs) on stochastic gravitational waves (GWs) induced by scalar perturbations. We consider the case where PBHs once dominated the Universe but eventually evaporated before the big bang nucleosynthesis. The reheating through the PBH evaporation could end with a sudden change in the equation of state of the Universe compared to the conventional reheating caused by particle decay. We show that this “sudden reheating” by the PBH evaporation enhances the induced GWs, whose amount depends on the length of the PBH-dominated era and the width of the PBH mass function. We explore the possibility to constrain the primordial abundance of the evaporating PBHs by observing the induced GWs. We find that the abundance parameter $\beta \gtrsim {10}^{-5}-{10}^{-8}$ for $𝒪({10}^3-10^5)\mathrm{g}$ PBHs can be constrained by future GW observations if the width of the mass function is smaller than about a hundredth of the mass.

Big-bang nucleosynthesis (BBN) is valuable as a means to constrain the physics of the early universe and it is the only probe of the radiation-dominated epoch. A fundamental assumption in BBN is that the nuclear velocity distributions obey Maxwell-Boltzmann (MB) statistics as they do in stars. Specifically, the BBN epoch is characterized by a dilute baryon plasma for which the velocity distribution of nuclei is mainly determined by the dominant Coulomb elastic scattering with mildly relativistic electrons. One must therefore deduce the momentum distribution for reacting nuclei from the multicomponent relativistic Boltzmann equation. However, the full multicomponent relativistic Boltzmann equation has only recently been analyzed and its solution has only been worked out in special cases. Moreover, a variety of schemes have been proposed that introduce nonthermal components into the BBN environment which can alter the thermal distribution of reacting nuclei. Here, we construct the relativistic Boltzmann equation in the context of BBN. We also derive a Langevin model and perform relativistic Monte-Carlo simulations which clarify the baryon distribution during BBN and can be used to analyze any relaxation from a nonthermal injection. We show by these analyses that the thermalization process leads to a nuclear distribution function that remains very close to MB statistics even during the most relativistic environment relevant to BBN. Hence, the predictions of standard BBN remain unchanged.

We introduce a novel methodology for establishing the presence of standing accretion shock instabilities (SASI) in the dynamics of a core collapse supernova from the observed neutrino event rate at water- or ice-based neutrino detectors. The methodology uses a likelihood ratio in the frequency domain as a test-statistics; it is also employed to assess the potential to estimate the frequency and the amplitude of the SASI modulations of the neutrino signal. The parameter estimation errors are consistent with the minimum possible errors as evaluated from the inverse of the Fisher information matrix, and close to the theoretical minimum for the SASI amplitude. Using results from a core-collapse simulation of a 15 solar-mass star by Kuroda et al. [Astrophys. J. 851, 62 (2017).] as a test bed for the method, we find that SASI can be identified with high confidence for a distance to the supernova of up to $\sim 6\mathrm{kpc}$ for IceCube and up to $\sim 3\mathrm{kpc}$ for a 0.4 Mt mass water Cherenkov detector. This methodology will aid the investigation of a future galactic supernova.

In this work, we make a theoretical study on the $p\overline{p}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}\eta$ reaction for antiproton beam energy from threshold to 4 GeV within an effective Lagrangian approach and isobar model. By assuming this reaction is dominated by the excitation of $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ resonances in intermediate states, we calculate the total cross sections and give the predictions of the angular distribution and invariant mass spectrum of final particles. In particular, we discuss the possibility to verify the existence of a narrow $\mathrm{\Lambda }$ resonance found in the process of $K^{-}p\to \eta \mathrm{\Lambda }$ in the present reaction. It shows that the $p\overline{p}\to \overline{\mathrm{\Lambda }}\mathrm{\Lambda }\eta$ reaction can provide us with valuable information about the $\mathrm{\Lambda }$ resonances having significant couplings to $\overline{K}N$ and $\mathrm{\Lambda }\eta$ channels. Thus the experimental data of this reaction will be a good supplement to the $\overline{K}N\to \eta \mathrm{\Lambda }$ scattering data for studying $\mathrm{\Lambda }$ resonances.