Various properties of acoustic black holes constructed in Minkowski spacetime have been widely studied in the past decades. Recently the acoustic black holes in general spacetime were proposed. In this paper, we first investigate the basic characteristics of “curved” acoustic black holes in Schwarzschild spacetime, including the quasinormal modes, grey-body factor, and analogous Hawking radiation. We find that the signal of the quasinormal mode is weaker than that of the Schwarzschild black hole. Moreover, as the tuning parameter increases, both the positive real part and negative imaginal part of the quasinormal frequency approach to the horizonal axis, but they will not change sign. This means that all the perturbations could die off and the system is stable under those perturbations. Since the larger tuning parameter suppresses the effective potential barrier, so it enhances the grey-body factor. The energy emission rate of Hawking radiation does not monotonically increase the tuning parameter because of the nonmonotonicity of the Hawking temperature. Finally, as a first attempt, we study the acoustic black hole shadow. The radius of the acoustic shadow becomes larger as the tuning parameter increases because both the related acoustic horizon and the acoustic sphere become larger. Our studies could help us to further understand the near horizon geometrical features of the black hole. We also expect that our observations could be detected experimentally in the near future.

We pioneer the black hole mass gap as a powerful new tool for constraining modified gravity theories. These theories predict fifth forces that alter the structure and evolution of population-III stars, exacerbating the pair-instability. This results in the formation of lighter astrophysical black holes and lowers both the upper and lower edges of the mass gap. These effects are explored using detailed numerical simulations to derive quantitative predictions that can be used as theoretical inputs for Bayesian data analysis. We discuss detection strategies in light of current and upcoming data as well as complications that may arise due to environmental screening. To demonstrate the constraining power of the mass gap, we present a novel test of the strong equivalence principle where we apply our results to an analysis of the first ten LIGO/Virgo binary black hole merger events to obtain a 7% bound on the relative difference between the gravitational constant experienced by baryonic matter, and that experienced by black holes, $\mathrm{\Delta }G/G$. The recent GW190521 event resulting from two black holes with masses in the canonical mass gap can be explained by modified gravity if the event originated from an unscreened galaxy where the strength of gravity is either enhanced or reduced by $\sim 30\%$ relative to its strength in the Solar System.

We show that a specific gauge choice comes extremely close to defining a frame whose preferred observers see a dipole-free cosmic microwave background (CMB). In this gauge the metric is the product of a scale factor depending on all spacetime coordinates, and a metric featuring an expansion-free geodesic timelike vector field. This setup facilitates the computation of redshift and other distance measures and may help to explain why we can have a highly isotropic CMB despite large inhomogeneities.

We present a phase-space analysis of the qualitative dynamics cosmologies where dark matter exchanges energy with the vacuum component. We find fixed points corresponding to power-law solutions where the different components remain a constant fraction of the total energy density and given an existence condition for any fixed points with nonvanishing energy transfer. For some interaction models we find novel fixed points in the presence of a third noninteracting fluid with constant equation of state, such as radiation, where the interacting $\mathrm{vacuum}+\mathrm{matter}$ tracks the evolution of the third fluid, analogous to tracker solutions previously found for self-interacting scalar fields. We illustrate the phase-plane behavior, determining the equation of state and stability of the fixed points in the case of a simple linear interaction model, for interacting vacuum and dark matter, including the presence of noninteracting radiation. We give approximate solutions for the equation of state in matter- or vacuum-dominated solutions in the case of small interaction parameters.

Higgs inflation is known to be a minimal extension of the Standard Model allowing for the description of the early Universe inflation. This model is considered an effective field theory since it has a relatively low cutoff scale, thus requiring further extensions to be a valid description of the reheating phase. We present a novel unified approach to the problem of unitarization and UV completion of the Higgs inflation model without introducing new massive degrees of freedom. This approach is based on an Analytic Infinite Derivative modification of the Higgs field kinetic term. We construct a unitary nonlocal UV completion of the original Higgs inflation model, while the inflationary stage is kept stable with respect to quantum corrections.

We investigate the capability of the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) in performing target-of-opportunity (ToO) neutrino observations. POEMMA is a proposed space-based probe-class mission for ultrahigh-energy cosmic ray and very-high-energy neutrino detection using two spacecraft, each equipped with a large Schmidt telescope to detect optical and near-ultraviolet signals generated by extensive air showers (EASs). POEMMA will be sensitive to Cherenkov radiation from upward-moving EASs initiated by tau neutrinos interacting in the Earth. POEMMA will be able to quickly repoint (90° in 500 s) each of the two spacecrafts to the direction of an astrophysical source, which in combination with its orbital speed will provide it with unparalleled capability to follow-up transient alerts. We calculate POEMMA’s transient sensitivity for two observational configurations for the satellites (ToO-stereo and ToO-dual for smaller and larger satellite separations, respectively) and investigate the impact of variations arising due to POEMMA’s orbital characteristics on its sensitivity to tau neutrinos in various regions of the sky. We explore separate scenarios for long ($\sim 10^{5-6}\mathrm{s}$) and short ($\sim {10}^3\mathrm{s}$) duration events, accounting for intrusion from the Sun and the Moon in the long-duration scenario. We compare the sensitivity and sky coverage of POEMMA for ToO observations with those for existing experiments (e.g., IceCube, ANTARES, and the Pierre Auger Observatory) and other proposed future experiments (e.g., GRAND200k). For long bursts, we find that POEMMA will provide a factor of $\gtrsim 7$ improvement in average neutrino sensitivity above 300 PeV with respect to existing experiments, reaching the level of model predictions for neutrino fluences at these energies and above from several types of long-duration astrophysical transients (e.g., binary neutron star mergers and tidal disruption events). For short bursts, POEMMA will improve the sensitivity over existing experiments by at least an order of magnitude for $E_{\nu }\gtrsim 100\mathrm{PeV}$ in the “best-case” scenario. POEMMA’s orbital characteristics and rapid repointing capability will provide it access to the full celestial sky, including regions that will not be accessible to ground-based neutrino experiments. Finally, we discuss the prospects for POEMMA to detect neutrinos from candidate astrophysical neutrino sources in the nearby Universe. Our results demonstrate that with its improved neutrino sensitivity at ultrahigh energies and unique full-sky coverage, POEMMA will be an essential, complementary component in a rapidly expanding multimessenger network.

The Universe is awash with tens-of-MeV neutrinos of all species coming from all past core-collapse supernovae. These have never been observed, but this state of affairs will change in the near future. In less than ten years, the Super-Kamiokande experiment, loaded with gadolinium, is expected to collect dozens of events induced by the scattering of neutrinos from the diffuse supernova neutrino background (DSNB). Next-generation projects, including Hyper-Kamiokande and Theia, are expected to collect data samples with hundreds of DSNB events after a decade of running. Here, we study quantitatively how well the DSNB, including its energy spectrum, will be measured by different current or upcoming large neutrino detectors. We analyze the simulated data in order to estimate how well measurements of the DSNB can be used to inform research topics in cosmology—including measurements of the Hubble parameter—astrophysics—including the star-formation rate—and particle physics—including the neutrino lifetime and the possibility that neutrinos are pseudo-Dirac fermions.

Electromagnetic waves in a dynamical axion background exhibit superluminal group velocities at high frequencies and instabilities at low frequencies, altering how photons propagate through space. Local disturbances propagate causally, but unlike in ordinary Maxwell theory, propagation occurs inside as well as on the light cone. For the unstable modes, the energy density in the electromagnetic field grows exponentially along timelike displacements. In this paper we derive retarded Green functions in axion electrodynamics in various limits and study the time-domain properties of propagating signals.

LIGO and Virgo have recently observed a number of gravitational wave (GW) signals that are fully consistent with being emitted by binary black holes described by general relativity. However, there are theoretical proposals of exotic objects that can be massive and compact enough to be easily confused with black holes. Nevertheless, these objects differ from black holes in having nonzero tidal deformabilities, which can allow one to distinguish binaries containing such objects from binary black holes using GW observations. Using full Bayesian parameter estimation, we investigate the possibility of constraining the parameter space of such “black hole mimickers” with upcoming GW observations. Employing perfect fluid stars with a polytropic equation of state as a simple model that can encompass a variety of possible black hole mimickers, we show how the observed masses and tidal deformabilities of a binary constrain the equation of state. We also show how such constraints can be used to rule out binaries of some simple models of boson stars as possible sources of the simulated events we consider.

We study the spin and eccentricity evolution of black-hole (BH) binaries that are perturbed by tertiary masses and experience the Lidov-Kozai (LK) excitation. We focus on three aspects. First, we study the spin-orbit alignment of the inner binary following the approach outlined by Antonini et al. [Mon. Not. R. Astron. Soc. 480, L58 (2018)] and Liu and Lai [Astrophys. J. 863, 68 (2018)], yet allowing the spins to have random initial orientations. We confirm the existence of a dynamical attractor that drives the spin-orbit angle at the end of the LK evolution to a value given by the initial angle between the spin and the outer orbital angular momentum (instead of to a specific value of the effective spin). Second, we follow the (inner) binary’s evolution further to the merger to study the final spin-spin alignment. We generalize the effective potential theory to include orbital eccentricity, which allows us to efficiently evolve the system in the early inspiral stages. We further find that the spin-spin and spin-orbit alignments are correlated and the correlation is determined by the initial spin-orbit angle. For systems with the spin vectors initially in the orbital plane, the final spins strongly disfavor an aligned configuration and could thus lead to a greater value of the GW recoil than a uniform spin-spin alignment would predict. Lastly, we study the maximum eccentricity excitation that can be achieved during the LK process, including the effects of gravitational-wave radiation. We find that when the tertiary mass is a supermassive BH and the inner binary is massive, then even with the maximum LK excitation, the residual eccentricity is typically less than 0.1 when the binary’s orbital frequency reaches 10 Hz, and a decihertz detector would be necessary to follow such a system’s orbital evolution.

Holographic dark energy (HDE) describes the vacuum energy in a cosmic IR region whose total energy saturates the limit of avoiding the collapse into a black hole. HDE predicts that the dark energy equation of the state transiting from greater than the $-1$ regime to less than $-1$, accelerating the Universe slower at the early stage and faster at the late stage. We propose the HDE as a new physical resolution to the Hubble constant discrepancy between the cosmic microwave background (CMB) and local measurements. With Planck CMB and galaxy baryon acoustic oscillation (BAO) data, we fit the HDE prediction of the Hubble constant as $H_0=71.54\pm 1.78\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, consistent with local $H_0$ measurements by LMC Cepheid Standards (R19) at $1.4\sigma$ level. Combining $Planck+\mathrm{BAO}+\mathrm{R}19$, we find the HDE parameter $c=0.51\pm 0.02$ and $H_0=73.12\pm 1.14\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, which fits cosmological data at all redshifts. Future CMB and large-scale structure surveys will further test the holographic scenario.

In this work, we reappraise the collider constraints from leptonic final states on the vectorlike colored top partners taking into account the impact of exotic colored vector resonances. These colored states are intrinsic to a broad class of models that employ a strongly interacting sector to drive electroweak symmetry breaking. We translate the recent results in the $monolepton+jets$ channel as reported by CMS with an integrated luminosity of $35.8{\mathrm{fb}}^{-1}$, and $dilepton+jets$ and $trilepton+jets$ channels as reported by ATLAS with an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$ to constrain the parameter space of these class of models. We also comment on the impact and modification of the derived constraints due to the expected fatness of the colored vector resonance, when accounted for beyond the narrow-width approximation by simulating the full one-particle irreducible resummed propagator.

We examine the recently reported low-energy electron recoil spectrum observed at the XENON1T underground dark matter direct detection experiment, in the context of new interactions with solar neutrinos. In particular we show that scalar and vector mediators with masses $\lesssim 50\mathrm{keV}$ coupled to leptons could already leave a visible signature in the XENON1T experiment, similar to the observed peak below 7 keV. This signals that dark matter detectors are already competing with neutrino scattering experiments such as GEMMA, CHARM-II and Borexino. If these results from XENON1T are interpreted as a new signal of such physics, the parameters which fit the excess face challenges from astrophysics which seem very difficult to overcome. If they are rather viewed as a constraint on new couplings, they herald the start of an era of novel precise probes of physics beyond the Standard Model with dark matter detectors.

The interactions of dark matter (DM) with the visible sector are often phenomenologically described in the framework of simplified models, where the couplings of quarks to the new particles are generally assumed to be universal or have a simple structure motivated by observational benchmarks. They should, however, a priori be treated as free parameters. In this work, we discuss one particular realization of the structure of DM couplings based on an $S_4\times Z_5$ flavor symmetry, which has been shown to account reasonably well for fermion masses and mixing, and compare their effect on observational signals to universal as well as Yukawa-like couplings, which are motivated by a minimal flavor violation. We will also comment on how these structures could be constrained in UV complete theories of DM and how DM observables, such as, e.g., relic density and direct detection, can potentially be used as a smoking gun for the underlying flavor symmetries.

We study the minimal extension of the Standard Model by a scalar with quartic interaction serving as an inflaton. For the model where scale symmetry is broken only in the inflaton sector, the mass of the inflaton is constrained to be relatively low. Here, we analyze the previously omitted situation of the inflaton masses $m_{\chi }\gtrsim 250\mathrm{GeV}$. Then, we provide a window of inflaton masses with viable inflationary properties that evade direct observational constraints due to the small inflaton mixing with the Higgs sector. The addition of heavy neutral leptons with Majorana masses induced by the interaction with the inflaton allow for cold dark matter in the model with masses $O(1–10)\mathrm{MeV}$.

Violation of non-Abelian Bianchi identity can be regarded as $N^2-1$ Abelian-like monopole currents in the continuum SU(N) QCD. Three Abelian-like monopoles, when defined in SU(2) gluodynamics on the lattice à la DeGrand–Toussaint, are shown to have the continuum limit with respect to the color-invariant monopole density and the effective monopole action. Since each Abelian-like monopole is not gauge invariant, we have introduced various partial gauge fixing for the purpose of reducing lattice artifact monopoles in the thermalized vacuum. Here we investigate Abelian and monopole dominances and the Abelian dual Meissner effects adopting the same gauges like the maximal center gauge (MCG) in comparison with the maximal Abelian gauge (MAG). Abelian and monopole contributions to the string tension in these gauges are observed to be a little smaller than the non-Abelian string tension. However, we find that the monopole dominance is improved well when use is made of the block-spin transformations with respect to Abelian-like monopoles. We find each electric field is squeezed by the corresponding colored Abelian-like monopole in such gauges and the Abelian dual Meissner effect is observed independently for each color. Moreover, we confirm the dual Ampère’s law in these new gauges as well as in MAG. The SU(2) vacuum is shown to be near the border between the type 1 and type 2 dual superconductors. The penetration length is almost equal for the four gauge fixings, and the vacuum type in MCG is almost the same value as the previous results. These results are consistent with the previous results suggesting the continuum limit and the gauge-independence of Abelian monopoles.

We investigate the shear viscosity $\eta$ of the classical Yang-Mills (CYM) field on a lattice by using the Green-Kubo formula, where the shear viscosity is calculated from the time-correlation function of the energy-momentum tensor in equilibrium. Dependence of the shear viscosity $\eta (g,T)$ on the coupling $g$ and temperature $T$ is represented by a scaling function $f_{\eta }(g^{2}T)$ as $\eta (g,T)=T{f}_{\eta }(g^{2}T)$ due to the scaling-invariant property of the CYM. The explicit functional form of $f_{\eta }(g^{2}T)$ is successfully determined from the calculated shear viscosity: It turns out that $\eta (g,T)$ of the CYM field is proportional to $1/g^{1.10–1.88}$ at weak coupling, which is a weaker dependence on $g$ than that in the leading-order perturbation theory but consistent with that of the “anomalous viscosity” $\eta \propto 1/g^{1.5}$ under the strong disordered field. The obtained shear viscosity is also found to be roughly consistent with that estimated through the analysis of the anisotropy of the pressure of the CYM dynamics in the expanding geometry with recourse to a hydrodynamic equation.

We evaluate the phenomenological applicability of the dynamical grooming technique, introduced by Y. Mehtar-Tani, A. Soto-Ontoso, and K. Tywoniuk [Phys. Rev. D 101, 034004 (2020)], to boosted $W$ and top tagging at LHC conditions. An extension of our method intended for multiprong decays with an internal mass scale, such as the top quark decay, is presented. First, we tackle the reconstruction of the mass distribution of $W$ and top jets quantifying the smearing due to pileup. When compared to state-of-the-art grooming algorithms like SoftDropand its recursive version, dynamical grooming shows an enhanced resilience to background fluctuations. In addition, we assess the discriminating power of dynamical grooming to distinguish $W$ (top) jets from QCD ones by performing a two-step analysis: introduce a cut on the groomed mass around the $W$ (top) mass peak followed by a restriction on the N-subjettinnes ratio ${\tau }_{21}$ (${\tau }_{32}$). For $W$ jets, the out-of-the-box version of dynamical grooming results in a comparable performance to SoftDrop. Regarding the top tagger efficiency, 3-prong dynamical grooming, in spite of its simplicity, presents better performance than SoftDrop and similar results to recursive SoftDrop.

We study factorization in single transverse spin asymmetries for dijet production in proton-proton collisions, by considering soft gluon radiation at one-loop order. We show that the associated transverse momentum dependent (TMD) factorization is valid at the leading logarithmic level. At next-to-leading-logarithmic (NLL) accuracy, however, we find that soft gluon radiation generates terms in the single transverse spin-dependent cross section that differ from those known for the unpolarized case. As a consequence, these terms cannot be organized in terms of a spin independent soft factor in the factorization formula. We present leading logarithmic predictions for the single transverse spin dijet asymmetry for $pp$ collisions at RHIC, based on quark Sivers functions constrained by semi-inclusive deep inelastic scattering data. We hope that our results will contribute to a better understanding of TMD factorization breaking effects at NLL accuracy and beyond.

Within the framework of Dyson-Schwinger equations of QCD, we study the effect of finite volume on the chiral phase transition in a sphere with the MIT boundary condition. We find that the chiral quark condensate $⟨\overline{\psi }\psi ⟩$ and pseudotransition temperature $T_{pc}$ of the crossover decreases as the volume decreases, until there is no chiral crossover transition at last. We find that the system for $R=\infty \mathrm{fm}$ is indistinguishable from $R=10\mathrm{fm}$ and there is a significant decrease in $T_{pc}$ with $R$ as $R<4\mathrm{fm}$. When $R<1.5\mathrm{fm}$, there is no chiral transition in the system.