An accelerated boundary correspondence (ABC) is solved for the de Sitter moving mirror cosmology. The beta Bogoliubov coefficients reveal the particle spectrum is a Planck distribution with temperature inversely proportional to horizon radius. The quantum stress tensor indicates a constant emission of energy flux consistent with eternal equilibrium, while the total energy carried by the particles remains finite. The curved spacetime transformation to flat spacetime with an accelerated boundary is illustrated, and also shown for anti-de Sitter (AdS) spacetime.

In this paper, we study the four-dimensional Einstein-Maxwell-dilaton theories in the Newman-Penrose (NP) formalism. We adapt the equations of motion into the NP formalism, and obtain the solution space that is asymptotic to the flat space-time. We then investigate the gravitational and electromagnetic memory effects. We find that the dilaton does not contribute to the displacement nor the kick memory effects, but it does contribute to the time-delayed memory effect.

The black hole uniqueness and the no-hair theorems imply that the quasinormal spectrum of any astrophysical black hole is determined solely by its mass and spin. The countably infinite number of quasinormal modes of a Kerr black hole are thus related to each other, and any deviations from these relations provide a strong hint for physics beyond the general theory of relativity. To test the no-hair theorem using ringdown signals, it is necessary to detect at least two quasinormal modes. In particular, one can detect the fundamental mode along with a subdominant overtone or with another angular mode, depending on the mass ratio and the spins of the progenitor binary. Also in the light of the recent discovery of GW190412, studying how the mass ratio affects the prospect of black hole spectroscopy using overtones or angular modes is pertinent, and this is the major focus of our study. First, we provide ready-to-use fits for the amplitudes and phases of both the angular modes and overtones as a function of mass ratio $q\in [0,10]$. Using these fits, we estimate the minimum signal-to-noise ratio for detectability, resolvability, and measurability of subdominant modes/tones. We find that performing black hole spectroscopy with angular modes is preferable when the binary mass ratio is larger than $q\approx 1.2$ (provided that the source is not located at a particularly disfavored inclination angle). For nonspinning, equal-mass binary black holes, the overtones seem to be the only viable option to perform a spectroscopy test of the no-hair theorem. However, this would require a large ringdown signal-to-noise ratio ($\approx 100$ for a 5% accuracy test with two overtones) and the inclusion of more than one overtone to reduce modeling errors, making black hole spectroscopy with overtones impractical in the near future.

We present several improvements to the Cauchy-characteristic evolution procedure that generates high-fidelity gravitational waveforms at ${\mathcal{I}}^{+}$ from numerical relativity simulations. Cauchy-characteristic evolution combines an interior solution of the Einstein field equations based on Cauchy slices with an exterior solution based on null slices that extend to ${\mathcal{I}}^{+}$. The foundation of our improved algorithm is a comprehensive method of handling the gauge transformations between the arbitrarily specified coordinates of the interior Cauchy evolution and the unique (up to Bondi-Metzner-Sachs group transformations) Bondi-Sachs coordinate system of the exterior characteristic evolution. We present a reformulated set of characteristic evolution equations better adapted to numerical implementation. In addition, we develop a method to ensure that the angular coordinates used in the volume during the characteristic evolution are asymptotically inertial. This provides a direct route to an expanded set of waveform outputs and is guaranteed to avoid pure-gauge logarithmic dependence that has caused trouble for previous spectral implementations of the characteristic evolution equations. We construct a set of Weyl scalars compatible with the Bondi-like coordinate systems used in characteristic evolution and determine simple, easily implemented forms for the asymptotic Weyl scalars in our suggested set of coordinates.

We compute scalar quasinormal mode (QNM) frequencies in rotating black hole solutions of the most general class of higher-derivative gravity theories to quartic order in the curvature that reduce to general relativity for weak fields and are compatible with its symmetries. The wave operator governing the QNMs is not separable, but we show one can extract the QNM frequencies by a projection onto the set of spheroidal harmonics. We have obtained accurate results for the quasinormal frequency corrections relative to Kerr for rotating black holes with dimensionless spins up to $\sim 0.7$. We also discuss to what extent our results carry over to the phenomenologically more relevant case of gravitational QNMs. Finally, we provide an ancillary computational package that allows one to generalize our calculations to any effective energy-momentum tensor arising from higher-derivative terms in the effective action.

We perform ($3+1$)-dimensional simulations of primordial black hole (PBH) formation starting from the spheroidal superhorizon perturbations. We investigate how the ellipticity (prolateness or oblateness) affects the threshold of PBH formation in terms of the peak amplitude of curvature perturbation. We find that, in the case of the radiation-dominated universe, the effect of ellipticity on the threshold is negligibly small for large amplitude of perturbations expected for PBH formation.

We investigate inflationary dynamics in the framework of the Einstein-Gauss-Bonnet gravity. In the model under consideration, the inflaton field is nonminimally coupled to the Gauss-Bonnet curvature invariant, so that the latter appears to be dynamically important. We consider a quartic potential for the inflaton field, in particular, the one asymptotically connected to the Higgs inflation, and a wider class of coupling functions not considered in the earlier work. Keeping in mind the observational bounds on the parameters—the amplitude of scalar perturbations $A_s$, spectral index $n_s$ and tensor-to-scalar ratio $r$, we demonstrate that the model a quartic potential and the proposed coupling function is in agreement with observations.

We study a dark matter production mechanism based on decays of a messenger WIMP-like state into a pair of dark matter particles that are self-interacting via exchange of a light mediator. Its distinctive thermal history allows the mediator to be stable and therefore avoid strong limits from the cosmic microwave background and indirect detection. A natural by-product of this mechanism is a possibility of a late time, i.e., after recombination, transition to subdominant dark radiation component through three-body and one-loop decays to states containing the light mediator. We examine to what extent such a process can help to alleviate the $H_0$ tension. Additionally, the mechanism can provide a natural way of constructing dark matter models with ultrastrong self-interactions that may positively affect the supermassive black hole formation rate. We provide a simple realization of the mechanism in a Higgs portal dark matter model and find a significant region of the parameter space that leads to a mild relaxation of the Hubble tension while simultaneously having the potential of addressing small-scale structure problems of $\mathrm{\Lambda }\mathrm{CDM}$.

We analyze the lepton flavor violating process $\mu \text{−}e$ conversion in the framework of the minimal R-symmetric supersymmetric standard model. The theoretical predictions are determined by considering the experimental constraint on parameter ${\delta }^{12}$ from the lepton flavor violating decay $\mu \to e\gamma$. The predictions for $\mathrm{CR}(\mu -e,\text{nucleus})$ in nuclei are not sensitive to $\tan \beta$ or $m_A$ and take values in a narrow region. The numerical results show that $\gamma$ penguins dominate the predictions on $\mathrm{CR}(\mu -e,\text{nucleus})$, and the contribution from Higgs penguins is insignificant. The $Z$ penguins and box diagrams are less dominant in the predictions on $\mathrm{CR}(\mu -e,\text{nucleus})$ in a large parameter region. For small squark mass parameter, the contribution from box diagrams is comparable with dipole contribution from $\gamma$ penguins. The theoretical predictions on conversion rate $\mathrm{CR}(\mu -e,\text{nucleus})$ in an Al or Ti target can be enhanced close to the future experimental sensitivities and are very promising to be observed in near future experiments.

The ratio of the strange quark momentum fraction $⟨x{⟩}_{s+\overline{s}}$ to that of light quark $u$ or $d$ in disconnected insertions (DI) is calculated on the lattice with overlap fermions on four domain wall fermion ensembles. These ensembles cover three lattice spacings, three volumes and several pion masses including the physical one, from which a global fitting is carried out. A complete nonperturbative renormalization and the mixing between the quark and glue operators are taken into account. We find the ratio to be $⟨x{⟩}_{s+\overline{s}}/⟨x{⟩}_{u+\overline{u}}(\mathrm{DI})=0.795(79)(77)$ at $\mu =2\mathrm{GeV}$ in the $\overline{\mathrm{MS}}$ scheme. This ratio can be used as a constraint to better determine the strange parton distribution especially in the small $x$ region in the global fittings of PDFs when the connected and disconnected sea are fitted and evolved separately, demonstrating a new way that connects lattice calculations with global analyses.

We investigate the low-temperature behavior of two-dimensional (2D) ${\mathrm{RP}}^{N-1}$ models, characterized by a global $\mathrm{O}(N)$ symmetry and a local ${\mathbb{Z}}_2$ symmetry. For $N=3$ we perform large-scale simulations of four different 2D lattice models: two standard lattice models and two different constrained models. We also consider a constrained mixed $\mathrm{O}(3)\text{−}{\mathrm{RP}}^2$ model for values of the parameters such that vector correlations are always disordered. We find that all these models show the same finite-size scaling (FSS) behavior, and therefore belong to the same universality class. However, these FSS curves differ from those computed in the 2D O(3) $\sigma$ model, suggesting the existence of a distinct 2D ${\mathrm{RP}}^2$ universality class. We also performed simulations for $N=4$, and the corresponding FSS results also support the existence of an ${\mathrm{RP}}^3$ universality class, different from the O(4) one.

We address the interplay between global and local gauge non-Abelian symmetries in lattice gauge theories with multicomponent scalar fields. We consider two-dimensional lattice scalar non-Abelian gauge theories with a local $\mathrm{SO}(N_c)$ ($N_c\ge 3$) and a global $\mathrm{O}(N_f)$ invariance, obtained by partially gauging a maximally $\mathrm{O}(N_f{N}_c)$-symmetric multicomponent scalar model. Correspondingly, the scalar fields belong to the coset $S^{N_f{N}_c-1}/\mathrm{SO}(N_c)$, where $S^N$ is the $N$-dimensional sphere. In agreement with the Mermin-Wagner theorem, these lattice $\mathrm{SO}(N_c)$ gauge models with $N_f\ge 3$ do not have finite-temperature transitions related to the breaking of the global non-Abelian $\mathrm{O}(N_f)$ symmetry. However, in the zero-temperature limit they show a critical behavior characterized by a correlation length that increases exponentially with the inverse temperature, similarly to nonlinear $\mathrm{O}(N)$ $\sigma$ models. Their universal features are investigated by numerical finite-size scaling methods. The results show that the asymptotic low-temperature behavior belongs to the universality class of the two-dimensional ${\mathrm{RP}}^{N_f-1}$ model.

We discuss the canonical approach for the study of QCD phase at finite densities and temperatures in the confinement phase. The canonical approach, which is a method to extrapolate observables calculated at pure imaginary chemical potentials to those at real chemical potentials, is useful to overcome the sign problem in lattice QCD simulations at finite density. To validate the applicability of the approach, we employ the Nambu-Jona-Lasinio (NJL) and Polyakov-NJL (PNJL) models where exact solutions for the number density are available, which is the basic input of the fugacity expansion and can be compared with those of the canonical approach. We find that the number densities computed from the canonical approach are consistent with the exact solutions in most of the confinement phase. The results in the present study are applicable to the study of lattice QCD.

We derive the chiral effective Lagrangian for heavy-light mesons in the heavy quark limit from QCD under proper approximations. The low energy constants in the effective Lagrangian are expressed in terms of the light quark self-energy. With typical forms of the running coupling constant of QCD and the quark self-energy obtained from Dyson-Schwinger equations as well as lattice QCD, we estimate the low energy constants in the model and the strong decay widths. A comparison with data and some discussions of the numerical results are presented.

We study the nonleptonic two-body weak decays of ${\mathrm{\Lambda }}_b$ by modifying the MIT bag model without introducing new parameters to construct the momentum eigenstates of the baryons. We find that the branching ratios of ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{\pi }^{-}$, ${\mathrm{\Lambda }}_c^{+}{K}^{-}$, $p{\pi }^{-}$, and $p{K}^{-}$ are $(4.5\pm 0.2)\times {10}^{-3}$, $(3.4\pm 0.1)\times {10}^{-4}$, $(5.0\pm 0.5)\times {10}^{-6}$, and $(6.0\pm 0.7)\times {10}^{-6}$, which are all consistent with the current experimental data, respectively. We also explore $P$ and $CP$ asymmetries for the decays of ${\mathrm{\Lambda }}_b^0\to p({\pi }^{-},K^{-})$. In particular, we obtain that the direct $CP$-violating rate asymmetries in ${\mathrm{\Lambda }}_b^0\to p{\pi }^{-}$ and ${\mathrm{\Lambda }}_b^0\to p{K}^{-}$ are around $-4.4\%$ and 6.7%, in comparison with $(-2.5\pm 2.9)\%$ and $(-2.5\pm 2.2)\%$ from the Particle Data Group in 2020, respectively.

This paper focuses on tetraquarks containing one heavy quark and one heavy antiquark in the formal limit where the heavy quark masses go to infinity. It extends the theoretical framework developed for a tetraquark containing two heavy quarks based on semiclassical analysis and the Born-Oppenheimer approximation. It is shown that, for sufficiently small light quark masses, parametrically narrow $q{\overline{q}}^{\prime }Q\overline{Q}$ tetraquarks must exist in the formal limit of arbitrarily large heavy quark masses. The analysis is model independent; it requires no assumptions about the structure of the state or the mechanism of its decay beyond what can be deduced directly from QCD. The formal analysis here is only directly applicable to tetraquarks with large angular momentum and hence does not directly apply to experimentally observed tetraquark candidates. We also discuss the condition needed for a version of the analysis to apply for low angular momenta states. Whether this condition holds can be explored via lattice calculations. Current lattice calculations suggest that the condition is not met. If these preliminary calculations are confirmed, there are strong implications for the nature of the observed tetraquark resonances containing $\overline{c}c$ or $\overline{b}b$ pairs. It raises the possibility that the observed tetraquarks exist and are narrow not because the charm and bottom quarks are extremely heavy, but because they are sufficiently light.

Nontrivial Bianchi identities with local magnetic sources are solved by recognizing that gauge potentials are sections rather than globally defined functions, but properly accounting for the source degrees of freedom requires a modification of the field strength. Following work by Teitelboim and by Cariglia and Lechner, we extend Dirac’s string formalism for monopoles to D-branes in type IIA and IIB string theory. We give novel derivations of brane-induced Chern-Simons terms in the supergravity actions, including a prescription for integrating over potentials in the presence of magnetic sources. We give a noncovariant formulation of the IIB theory, keeping only the independent degrees of freedom of the self-dual 4-form potential. Finally, it is well known that D8-branes source the mass parameter of IIA supergravity; we show that the additional couplings of the massive IIA supergravity, including on other D-brane worldvolumes, are a consequence of the corresponding Dirac branes.

The weak gravity conjecture implies the necessary existence of particles with charge-to-mass ratio $q/m\ge 1$ so that the extremal charged black hole can completely evaporate without leaving a dangerous stable extremal remnant while simultaneously not revealing a naked singularity along the way. In other words, this inequality ensures that the charge is emitted faster than the mass of a black hole, which is in turn coincidentally consistent with the fact that gravitational interaction for such parties is weaker than electromagnetic. To extend this argument to nonextremal black holes, we solve the problem of a charged shell of mass and charge ($m$, $q$) from a black hole with mass ($M$, $Q$). We find a more general condition $q/m\ge Q/M$, which obviously reduces to the weak gravity conjecture in the extremal limit; however, it relaxes the condition for complete evaporation of nonextremal black holes. This condition also allows us to directly relate the particle content of the theory with the spectrum of black hole states.

We discuss an isomorphism between the possible anomalies of ($d+1$)-dimensional quantum field theories with ${\mathbb{Z}}_2$ unitary global symmetry, and those of $d$-dimensional quantum field theories with time-reversal symmetry $\mathsf{T}$. This correspondence is an instance of symmetry defect decoration. The worldvolume of a ${\mathbb{Z}}_2$ symmetry defect is naturally invariant under $\mathsf{T}$, and bulk ${\mathbb{Z}}_2$ anomalies descend to $\mathsf{T}$ anomalies on these defects. We illustrate this correspondence in detail for $(1+1)d$ bosonic systems where the bulk ${\mathbb{Z}}_2$ anomaly leads to a Kramers degeneracy in the symmetry defect Hilbert space and exhibits examples. We also discuss $(1+1)d$ fermion systems protected by ${\mathbb{Z}}_2$ global symmetry where interactions lead to a ${\mathbb{Z}}_8$ classification of anomalies. Under the correspondence, this is directly related to the ${\mathbb{Z}}_8$ classification of $(0+1)d$ fermions protected by $\mathsf{T}$. Finally, we consider $(3+1)d$ bosonic systems with ${\mathbb{Z}}_2$ symmetry where the possible anomalies are classified by ${\mathbb{Z}}_2\times {\mathbb{Z}}_2$. We construct topological field theories realizing these anomalies and show that their associated symmetry defects support anyons that can be either fermions or Kramers doublets.