We use the quasilocal formalism of Brown and York, supplemented with counterterms, to investigate the thermodynamics of asymptotically flat black holes. We consider two families of exact regular black hole solutions, which are thermodynamically stable. The first one consists of four-dimensional static charged hairy black holes in extended supergravity. The second family consists of five-dimensional static charged black holes in Gauss-Bonnet (GB) gravity. Despite the fact that their characteristics are completely different, we found a striking similarity between their thermodynamic behavior.

In this work, we delve into the model of the shift symmetric and parity-preserving beyond Horndeski theory in all its generality. We present an explicit algorithm to extract static and spherically symmetric black holes with primary scalar charge adhering to the conservation of the Noether current emanating from the shift symmetry. We show that when the functionals $G_2$ and $G_4$ of the theory are linearly dependent, analytic homogeneous black-hole solutions exist, which can become regular by virtue of the scalar charge contribution. Such geometries can easily enjoy the preservation of the weak energy conditions, elevating them into healthier compact objects than most hairy black holes in modified theories of gravity. Finally, we revisit the concept of disformal transformations as a solution-generating mechanism and discuss the case of generic $G_2$ and $G_4$ functionals.

This paper aims to investigate charged spherically symmetric static black holes in the Lyra geometry, in which a scale function naturally arises in the metric and affine structure of these types of manifolds. In particular, it utilizes the appropriate generalization of general relativity, the recently proposed Lyra scalar-tensor theory (LyST). The simplest generalization of Maxwell electrodynamics for Lyra manifolds is considered. An analytic solution for the line element of a Reissner-Nordström LyST generalization is presented. It is shown that, due to the natural presence of a scale radius, it is possible to have three different extremal charges for positive or negative charge intervals. As a consequence, in natural units, the equality of the mass and charge defined on Lyra manifolds does not give rise to an extremal black hole, which allows the existence of solutions in which the charge is greater than the mass. An analysis with charged test particles indicates that a finite positive Lyra parameter, referred as the Lyra scale radius in this case, possibly allows for a violation of the weak cosmic censorship on Lyra manifolds. It is shown that an extremal black hole can be overcharged to the point that the emergence of a naked singularity becomes possible. The same behavior is observed for negative values of this parameter if its absolute value is greater than 4 times the black hole mass. Notably, this investigation also shows that an eternal black hole can exist for any charge increase if the Lyra parameter is sufficiently close to some critical values.

The response of black holes to small perturbations is known to be partially described by a superposition of quasinormal modes. Despite their importance to enable strong-field tests of gravity, little to nothing is known about what overtones and quasinormal-mode amplitudes are like for black holes in extensions to general relativity. We take a first step in this direction and study what is arguably the simplest model that allows first-principle calculations to be made: a nonrotating black hole in an effective-field-theory extension of general relativity with cubic-in-curvature terms. Using a phase-amplitude scheme that uses analytical continuation and the Prüfer transformation, we numerically compute, for the first time, the quasinormal overtone frequencies (in this theory) and quasinormal-mode excitation factors (in any theory beyond general relativity). We find that the overtone quasinormal frequencies and their excitation factors are more sensitive than the fundamental mode to the length scale $l$ introduced by the higher-derivative terms in the effective field theory. We argue that a description of all overtones cannot be made within the regime of validity of the effective field theory, and we conjecture that this is a general feature of any extension to general relativity that introduces a new length scale. We also find that a parametrization of the modifications to the general-relativistic quasinormal frequencies in terms of the ratio between $l$ and the black hole’s mass is somewhat inadequate, and we propose a better alternative. As an application, we perform a preliminary study of the implications of the breakdown, in the effective field theory, of the equivalence between the quasinormal mode spectra associated to metric perturbations of polar and axial parity of the Schwarzschild black hole in general relativity. We also present a simple justification for the loss of isospectrality.

In the curved spacetime background, the trajectory of a spinning test particle will deviate from the geodesic. Using the effective potential method, we study the motion of a spinning test particle on the equatorial plane of a polymer black hole in loop quantum gravity described by the Mathisson-Papapetrou-Dixon equations with minimal spin-gravity interaction. We find that for the bounded orbits in the radial direction, the particle’s motion is timelike when its spin is small. The radial range of the orbit and its eccentricity decrease with the loop quantum gravity parameter. However, when the particle takes a large enough spin, we observe an interesting phenomenon that the timelike and spacelike motions alternately appear while are separated by a critical radius. Outside the critical radius, the motion is timelike; however inside it is spacelike, and on the radius $r_c$ it is null. This property shares similarities with the event horizon radius. However, unlike the event horizon radius, the value of $r_c$ is related to both the particle’s motion and the black hole parameters. To explore more observable effects of the loop quantum gravity parameter on the motion of the spinning particle, we focus our attention on the circular orbits, particularly the innermost stable circular orbits, near the black hole. The result shows that for the same spin, there are two different innermost stable circular orbits, one with a larger radius and the other with a smaller radius. Both the radii decrease as the loop quantum gravity parameter increases. More significantly, with the increase of the spin of the particle, the small innermost stable circular orbit transition from timelike to spacelike, while the one with large radius does not. Instead, it terminates at a certain value of spin. Furthermore, we identify the existence of a minimal spin value, below which the innermost stable circular orbits maintain a timelike motion irrespective of the loop quantum gravity parameter. All the results present the significant influences of the loop quantum gravity parameter on the motion of the spinning particles.

Cosmological models featuring an elastic interaction in the dark sector have been shown to provide a promising scenario for alleviating the ${\sigma }_8$ tension. A natural question for these scenarios is whether there could be a degeneracy between the interaction and massive neutrinos since they suppress structures in a similar manner. In this work we investigate the presence of such a degeneracy and show that the two effects do not exhibit strong correlations.

We apply the convolutional neural networks (CNNs) to the mock 21 cm maps from the post-reionization epoch to show that the $\mathrm{\Lambda }$ cold dark matter and warm dark matter (WDM) model can be distinguished for WDM particle masses $m_{\mathrm{FD}}<3\mathrm{keV}$, under the assumption of thermal production of WDM following the Fermi-Dirac (FD) distribution. We demonstrate that the CNN is a potent tool in distinguishing the dark matter masses, highlighting its sensitivity to the subtle differences in the 21 cm maps produced by varying dark matter masses. Furthermore, we extend our analysis to encompass different WDM production mechanisms, recognizing that the dark matter production mechanism in the early Universe is among the sources of the most significant uncertainty for the dark matter model building. In this work, given the mass of the dark matter, we discuss the feasibility of discriminating four different WDM models: Fermi-Dirac (FD) distribution model, neutrino Minimal Standard Model ($\nu \mathrm{MSM}$), Dodelson-Widrow (DW), and Shi-Fuller (SF) model. For instance, when the WDM mass is 2 keV, we show that one can differentiate between CDM, FD, $\nu \mathrm{MSM}$, and DW models while discerning between the DW and SF models turns out to be challenging. Our results reinforce the viability of the CNN as a robust analysis for 21 cm maps and shed light on its potential to unravel the features associated with different dark matter production mechanisms.

The growth-rate $f{\sigma }_8(z)$ of the large-scale structure of the Universe is an important dynamic probe of gravity that can be used to test for deviations from general relativity. However, for galaxy surveys to extract this key quantity from cosmological observations, two important assumptions have to be made: (i) a fiducial cosmological model, typically taken to be the cosmological constant and cold dark matter model and (ii) the modeling of the observed power spectrum, especially at nonlinear scales, which is particularly dangerous as most models used in the literature are phenomenological at best. In this work, we propose a novel approach involving convolutional neural networks (CNNs), trained on the Quijote $N$-body simulations, to predict $f{\sigma }_8(z)$ directly and without assuming a model for the nonlinear part of the power spectrum, thus avoiding the second of the assumptions above. This could serve as an initial step towards the future development of a method for parameter inference in stage IV surveys. We find that the predictions for the value of $f{\sigma }_8$ from the CNN are in excellent agreement with the fiducial values since they outperform a maximum likelihood analysis and the CNN trained on the power spectrum. Therefore, we find that the CNN reconstructions provide a viable alternative to avoid the theoretical modeling of the nonlinearities at small scales when extracting the growth rate.

We present a full model of surface-detector responses to extensive air showers. The model is motivated by the principles of air-shower universality and can be applied to different types of surface detectors. Here we describe a parametrization for both water-Cerenkov detectors and scintillator surface detectors, as for instance employed by the upgraded detector array of the Pierre Auger Observatory. Using surface detector data, the model can be used to reconstruct with reasonable precision shower observables such as the depth of the shower maximum $X_{\max }$ and the number of muons $R_{\mu }$.

PandaX-4T experiment is a deep-underground dark matter direct search experiment that employs a dual-phase time projection chamber with a sensitive volume containing 3.7 tonne of liquid xenon. The detector of PandaX-4T is capable of simultaneously collecting the primary scintillation and ionization signals, utilizing their ratio to discriminate dark matter signals from background sources such as gamma rays and beta particles. The signal response model plays a crucial role in interpreting the data obtained by PandaX-4T. It describes the conversion from the deposited energy by dark matter interactions to the detectable signals within the detector. The signal response model is utilized in various PandaX-4T results. This work provides a comprehensive description of the procedures involved in constructing and parameter-fitting the signal response model for the energy range of approximately 1 keV to 25 keV for electronic recoils and 6 keV to 90 keV for nuclear recoils. It also covers the signal reconstruction, selection, and correction methods, which are crucial components integrated into the signal response model.

The recent measurements of the spectral intensities of cosmic-ray nuclei have suggested that the ratio of boron to carbon nuclei, $R(E)$, comprises two components, $R_1(E)$ which carries all of the energy dependence and the other $R_A$, a constant independent of energy per nucleon. This finding supports the earlier theoretical expectations and results of gamma-ray astronomy that one of these components is attributable to spallation in a cocoon like region surrounding the sources and the other in the general interstellar medium before cosmic rays leak away from the Galaxy. A new model-independent way of analyzing cosmic-ray spectra is presented here to shed light on the recent findings: Imposing the single constraint that the source function of B nuclei is minimal we use a cascade of rate equations to map point by point the observed cosmic-ray spectra of p, B, C, O, and Fe onto their source spectra and the two lifetimes of cosmic rays ${\tau }_G$ in the Galaxy and ${\tau }_S$ in the cocoons surrounding the sources. The model-independent results show that the appropriate choice ${\tau }_S(E)$ is responsible for $R_1(E)$ and the source spectra are power laws with indices of $\sim -2.7$.

In a few recent papers we introduced the chirality-flow formalism, which builds on the spinor-helicity formalism, but incorporates the Fierz identity into the Feynman rules. Calculations at tree level are thereby trivial, often to the extent that it is possible to immediately write down a tree-level Feynman diagram in terms of spinor inner products. This simplification persists in tree-level computer implementations, giving very sizable speedups. In the present paper, we argue that there is also a significant simplification of the Lorentz structure at the one-loop level when using the four-dimensional formulation of the four-dimensional helicity scheme. As at tree level, the gauge reference vector for external gauge bosons, and the simplified Lorentz structure lead to significant shortening of the calculations. Additionally, we find that the possible terms in a tensor decomposition of loop integrals are highly constrained, and therefore the tensor reduction procedure is simplified.

A set of new methods are proposed here to directly detect light mass dark matter through its scattering with abundant atmospheric muons or accelerator beams. A first plan is to use the free cosmic-ray muons interacting with dark matter in a volume surrounded by tracking detectors, to trace the possible interaction between dark matter and muons. Secondly, the same device can be interfaced with domestic or international muon beams. Due to the much larger muon intensity and focused beam, it is anticipated that the detector can be made further compact, and the resulting sensitivity on dark matter searches will be improved. Furthermore, it may also be possible to measure precisely directional distributions of cosmic-ray muons, either at mountain or sea level, and the differences may reveal possible information about dark matter distributed near the Earth. Specifically, methods described here can have advantages over “exotic” dark matters that are either muonphilic or slowed down due to some mechanism, and the sensitivity on dark matter and muon scattering cross section can reach as low as microbarn level.

Light feebly interacting dark matter is widely predicted in a plethora of new physics models. However, due to very feeble couplings with the standard-model particles, its relic density produced via the relativistic thermal freeze-out process easily exceeds the observed value. The entropy dilution in an early matter-dominated era provides an attractive mechanism for solving such an overabundance problem. In this work, we note that this dark matter dilution mechanism will lead to two distinctive kinks in the primordial GW spectrum, whose frequencies strongly correlate with the DM mass. We show that the GW detectors, such as Cosmic Explorer (CE) and Big Bang Observer (BBO), can measure the kinks in the primordial GW spectrum and will offer a new avenue to probe light feebly interacting dark matter.

This paper investigates the impact of strangeness chemical potential and anisotropic momentum distribution on finite-size isospin asymmetric quark matter by employing a three-flavored Polyakov quark meson model. The model incorporates scalar and vector interactions to investigate the critical endpoint (CEP) and the susceptibilities of conserved charges in isotropic and anisotropic medium. The chiral critical point in the QCD phase diagram is found to be shifted toward higher values of the quark chemical potential (${\mu }_q$) and lower temperature (T) for decreasing system size. On the other hand, there is an opposite change to lower quark chemical potential and higher temperature for decreasing strangeness chemical potential. The impact of anisotropic momentum distribution is discussed in terms of anisotropy parameter, $\xi$. It is found that as the value of $\xi$ increases toward a positive value, the chiral phase boundary becomes a crossover. The Polyakov loop potential is introduced in the model to analyze the change in the deconfinement transition line.

We introduce and investigate the color chiral Cherenkov effect which consists in radiation of the circularly polarized gluons by a fast color charge moving with constant velocity in the presence of the chiral magnetic current. We derive the transition rates for all gluon polarizations. We compute the contribution of the color chiral Cherenkov effect to the parton energy loss in the quark-gluon plasma.

In this work, the production of the hidden-strange pentaquarklike state, $N^{*}(2080)$, via the ${\pi }^{-}p$ scattering process is studied by the effective Lagrangian approach. Concretely, we consider the $\rho$ meson exchange of $t$-channel and the nucleon exchange of $u$-channel, which are treated as the background terms, and take into account the contribution of the $N^{*}(2080)$ via the $s$-channel as a signal term. By global fitting of the total and differential cross sections of the ${\pi }^{-}p\to \varphi n$ process, it is shown that the $N^{*}(2080)$ contributes an obvious peak at the threshold energy point of the differential cross section at the forward angle ($\cos \theta =1$), which provides clues to the detection of the $N^{*}(2080)$ by the ${\pi }^{-}p$ scattering process. However, due to the limited accuracy of the experimental data, it is an objective limitation for us to determine the properties of the $N^{*}(2080)$ by the ${\pi }^{-}p$ scattering process. Therefore, more accurate experimental measurements of the ${\pi }^{-}p\to \varphi n$ reaction are highly desirable, and we have also proposed that correlation measurements can be performed on J-PARC, AMBER, and future HIKE and HIAF meson beam experiments.

Exclusive $C=+1$ scalar, axial-vector, and tensor quarkonium production in high-energy electron-proton scattering requires a $C$-odd $t$-channel exchange of a photon or a three-gluon ladder. We derive the expressions for the corresponding amplitudes. The relative phase of the photon vs three-gluon exchange amplitudes is determined by the sign of the light-front matrix element of the eikonal color current operator $d^{abc}{J}^{+a}{J}^{+b}{J}^{+c}$ at moderate $x$, and is not affected by small-$x$ QCD evolution. Model calculations predict constructive interference, which is particularly strong for momentum transfer $|t|\sim 1{\mathrm{GeV}}^2$ where the cross section for ${\chi }_{cJ}$ production exceeds that for pure photon exchange by up to a factor of 4. Exclusive ${\chi }_{cJ}$ electroproduction at the high luminosity Electron-Ion Collider occurs with well measurable rates and measurements of these processes should find evidence for the perturbative odderon exchange. We also compute the total electroproduction cross section as a function of energy and provide first estimates of the number of ${\chi }_{cJ}$ events per month at the Electron-Ion Collider design luminosity.

We studied the Hayden-Preskill thought experiment with the local projective measurement. Compared to the original model, the measurement is applied to the Hawking radiation that was emitted after throwing the quantum diary into the black hole. Within this setup, we explored the information recovery from the black hole utilizing the Yoshida-Kitaev probabilistic strategy and demonstrated a perfect decoding in the ideal case. Additionally, we analyzed the decoherence effects from the environment on the decoding protocol. It shows that errors represented by the depolarizing channel can reduce the decoding probability and fidelity, while errors represented by the dephasing channel do not affect the decoding protocol. Furthermore, we discussed various aspects of the current model, including its relation to the black hole final state proposal and the quantum simulations of the decoding protocols. Especially, employing the graphical representations, we provide an intuitive derivation of the equivalence between the Yoshida-Kitaev protocol and Petz recovery map.

Using spacetime Gaussian test functions, we find closed-form expressions for the smeared Wightman function, Feynman propagator, retarded and advanced Green’s functions, causal propagator, and symmetric propagator of a massless scalar field in the vacuum of Minkowski spacetime. We apply our results to localized quantum systems that interact with a quantum field in Gaussian spacetime regions and study different relativistic quantum information protocols. In the protocol of entanglement harvesting, we find a closed-form expression for the entanglement that can be acquired by probes that interact in Gaussian spacetime regions and obtain asymptotic results for the protocol. We also revisit the case of two gapless detectors and show that the detectors can become entangled if there is two-way signalling between their interaction regions, providing closed-form expressions for the detectors’ final state.