We investigate $\pi \rho$ scattering based on the coupled-channel formalism with the $\pi \rho$ and $K{\overline{K}}^{*}$ ($\overline{K}{K}^{*}$) channels included. We construct the kernel amplitudes by using the meson-exchange model and compute the coupled integral equation for $\pi \rho$ scattering. By performing the partial-wave expansion, we show explicitly that the $a_1(1260)$ meson is dynamically generated by the coupled-channel formalism. The $a_1$ meson only appears by including the $K{\overline{K}}^{*}$ ($\overline{K}{K}^{*}$) channel. We obtain the pole position of the $a_1$ meson as $\sqrt{s_R}=(1170.7-i173.0)\mathrm{MeV}$. We conclude that the $a_1$ meson can be interpreted as a kaon and vector kaon molecular state.

The light front densities of momentum, angular momentum, and intrinsic pressure are calculated for the photon, both in the free case and at leading order in quantum electrodynamics. In the latter case, we moreover decompose the form factors into photon and electron contributions. Circularly and linearly polarized photons are both considered, with the latter containing significant azimuthal modulations in both the momentum density and in intrinsic stresses. We find that the $D$-term of the photon is positive instead of negative, and accordingly the intrinsic radial pressure of the photon is negative. Despite this, the radiation pressure exerted by the photon is positive. We illustrate through explicit calculation how the intrinsic pressure associated with the $D$-term and the radiation pressure exerted by the photon are different quantities.

Densities associated with the energy-momentum tensor are calculated for spin-one targets. These calculations are done in a light front formalism, which accounts for relativistic effects due to boosts and allows for arbitrary spatial localization of the target. These densities include the distribution of momentum, angular momentum, and pressures over a two-dimensional plane transverse to the light front. Results are obtained for both longitudinally and transversely polarized targets, and the formalism is tailored to allow the possibility of massless targets. The momentum density and pressure distributions are calculated for a deuteron target in a light cone convolution model, with which the properties of this model (such as helicity dependence of the densities) is illustrated.

The decays $J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and $\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ are observed for the first time, using $(10087\pm 44)\times {10}^{6}J/\psi$ and $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII collider. We determine the branching fractions of these two decays to be $\mathcal{B}(J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})=(6.34\pm 0.21\pm 0.37)\times {10}^{-5}$ and $\mathcal{B}(\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})=(9.59\pm 2.37\pm 0.61)\times {10}^{-6}$, where the first uncertainties are statistical and the second are systematic. The ratio of these two branching fractions is determined to be $\frac{\mathcal{B}(\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})}{\mathcal{B}(J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})}=(15.1\pm 3.8)\%$, which is in agreement with the “12% rule.”

A big open problem in ${\mathrm{AdS}}_3\times S^3\times T^4$ holographic duality is to compute the conformal field theory (CFT) data of the dual theory. In this direction in [B. Eden, D. l. Plat, and A. Sfondrini, J. High Energy Phys. 08 (2021) 049] it was introduced the hexagonalization framework in the ${\mathrm{AdS}}_3$ context. It allows the computation of the structure constants of the ${\mathrm{CFT}}_2$ dual in the planar limit nonperturbatively, however in [B. Eden, D. l. Plat, and A. Sfondrini, J. High Energy Phys. 08 (2021) 049] it was introduced only the asymptotic part of the hexagon valid for correlators with asymptotically large bridge lengths. In this work we complete this picture by computing the so called mirror corrections that allow to describe structure constants for finite bridge lengths and as a by-product we also prove that the half-BPS operators in the theory do not receive these corrections. We end up by giving the first steps on using hexagonalization to compute $n$-point functions in the ${\mathrm{AdS}}_3\times S^3\times T^4$ holographic duality.

We use a cosmological counterpart of the cylindrical Halilsoy solution to illustrate properties of cross-polarized standing gravitational waves.

We investigate the impact of radiation from primordial black holes (PBHs), in the mass range of ${10}^{15}\lesssim M_{\mathrm{PBH}}\lesssim {10}^{17}\mathrm{g}$ and ${10}^2\lesssim M_{\mathrm{PBH}}\lesssim {10}^4{M}_{\odot }$, on the 21-cm angular-power spectrum in the dark ages. PBHs in the former mass range affect the 21-cm angular-power spectrum through the evaporation known as Hawking radiation, while the radiation from the accretion process in the latter mass range. In the dark ages, radiation from PBHs can increase the ionization fraction and temperature of the intergalactic medium, change the global 21-cm differential brightness temperature and then affect the 21-cm angular-power spectrum. Taking into account the effects of PBHs, we find that in the dark ages, $30\lesssim z\lesssim 100$, the amplitude of the 21-cm angular-power spectrum is decreased depending on the mass and mass fraction of PBHs. We also investigate the potential constraints on the mass fraction of PBHs in the form of dark matter for the future radio telescope in lunar orbit or on the far side surface of the Moon.

Our observed Universe has a very strong arrow of time rooted in its low entropy starting point. This low entropy start can be related to various “tuning puzzles” about the early state of the Universe. Here we explore the relationship between the arrow of time and the emergence of classical from quantum in the hopes of ultimately gaining insights into cosmological initial conditions. Our focus is on einselection, the process whereby interactions with an environment select preferred states for a quantum system. This process plays an essential role in the emergence of classical from quantum. Studies of einselection have so far been limited to cases that exhibit an arrow of time. Here we study the ability of equilibrium systems to exhibit einselection—and investigate whether detailed balance prevents this—motivated by the question of whether classicality requires an arrow of time. We present calculations in the adapted Caldeira-Leggett model which demonstrate that einselection can indeed take place in equilibrium systems, and show how this phenomenon is tied to histories which express an arrow of time, despite the global equilibrium. We discuss some interesting implications of our results for cosmology and cosmological initial conditions. We are intrigued and a bit surprised by the role the consistent histories formalism has ended up playing in our analysis.

Quasicircular binary black hole mergers are described by 15 parameters, of which gravitational wave observations can typically constrain only $\sim 10$ independent combinations to varying degree. In this work, we devise coordinates that remove correlations, and disentangle well- and poorly-measured quantities. Additionally, we identify approximate discrete symmetries in the posterior as the primary cause of multimodality, and design a method to tackle this type of multimodality. The resulting posteriors have little structure and can be sampled efficiently and robustly. We provide a python package for parameter estimation, cogwheel, that implements these methods together with other algorithms for accelerating the inference process. One of the coordinates we introduce is a spin azimuth that is measured remarkably well in several events. We suggest this might be a sensitive indicator of orbital precession, and we anticipate that it will shed light on the occurrence of spin-orbit misalignment in nature.

The Einstein Telescope (ET), a future third-generation gravitational wave detector, will have detection sensitivity for gravitational wave signals down to 1 Hz. This improved low-frequency sensitivity of the ET will allow the observation of low mass binaries for a longer period of time in the detection band before their merger. Because of an improved sensitivity as compared to current and advanced 2G detectors, the detection rate will also be greatly improved. Given the high detection rate of merging compact binaries with the ET, it will be a useful instrument to conduct population studies. In this paper, we present an algorithm to estimate the parameters of the low mass merging compact binary systems such as localization, chirp mass, redshift, mass ratios, and total mass of the source, which are crucial in order to estimate the capability of the ET to study various compact binary populations. For the compact binary population distributed uniformly in comoving volume, we find that with single ET, $\approx 1\%$ of binaries can be localized within 800 square degrees. The values of chirp mass and total mass can be constrained within $\lesssim 5\%$ error, while $z$ and $D_L$ can be estimated with an error of $\lesssim 15\%$ for effective $\mathrm{SNR}\gtrsim 50$ using single ET.

Inspired by the very recently discovered tetraquark states $T_{c\overline{s}0}^a(2900{)}^{0,++}$ from the LHCb Collaboration, we predict the existence of a new charmed-strange pentaquark system, $c\overline{s}nnn$, which is closely connected to $c\overline{s}n\overline{n}$ by exchanging $\overline{n}$ into $nn$ with $n=u$, $d$. Especially, it is suggested to experimentally search for the predicted new pentaquark system via the weak decays of $B$ mesons or $b$ baryons, with the support from the study of the mass spectrum and the decay properties. The predicted new pentaquark system must attract extensive attention from experimentalists and theorists when it constructs the “particle zoo 2.0” in the near future.

The statistical mechanical calculation of the thermodynamical properties of nonrotating isolated horizons are studied in the loop quantum gravity framework. By employing the Hawking temperature and horizon mass of isolated horizons as physical inputs, the microcanonical ensemble associated with the system are well established. As a result, the black hole entropy and other thermodynamical quantities can be computed and are consistent with well-known Hawking’s semiclassical analysis. Moreover, the value of the Immirzi parameter of loop quantum gravity for the higher-dimensional case and four-dimensional U(1) case are also obtained.

We study the holographic quantum error correcting code properties of a Sierpinski triangle-shaped boundary subregion in ${\mathrm{AdS}}_4/{\mathrm{CFT}}_3$. Due to existing no-go theorems in topological quantum error correction regarding fractal noise, this gives holographic codes a specific advantage over topological codes. We then further argue that a boundary subregion in the shape of the Sierpinski gasket in ${\mathrm{AdS}}_5/{\mathrm{CFT}}_4$ does not possess these holographic quantum error correction properties.

This study investigates the quantumness of gravity under the setup of the atomic interferometry from the viewpoint of mass-energy equivalence. We evaluated interference visibility considering a particle with internal energy levels in a harmonic trapping potential. As per the result, for a spatially superposed gravitational source mass, interference visibility exhibits collapse and revival behavior, which implies that an initial separable internal state evolves to the entangled state with respect to the degrees of freedom of the center of mass, the internal energy levels, and the external source state. In particular, it does not exhibit revival behavior when gravity is treated as a quantum interaction, while it revives with a finite period for a semiclassical treatment of gravity. We also examined the temporal behavior of entanglement negativity and found that the nonrevival behavior of visibility reflects the creation of the entanglement between the internal energy state and the external source state which is uniquely induced by the quantum interaction of gravity in accordance with the weak equivalence principle.

Unruh DeWitt (UDW) detectors are important constructs in studying the dynamics of quantum fields in any geometric background. Curvature also plays an important role in setting up the correlations of a quantum field in a given spacetime. For instance, massless fields are known to have large correlations in de Sitter space as well as in certain class of Friedmann-Robertson-Walker (FRW) universes. However, some of the correlations are secular in nature while some are dynamic and spacetime dependent. An Unruh DeWitt detector responds to such divergences differently in different spacetimes. In this work, we study the response rate of Unruh DeWitt detectors which interact with quantum fields in FRW spacetimes. We consider both conventionally as well as derivatively coupled Unruh DeWitt detectors. Particularly, we consider their interaction with massless scalar fields in FRW spacetimes and nearly massless scalar fields in de Sitter spacetime. We discuss how the term which gives rise to the infrared divergence in the massless limit in de Sitter spacetime manifests itself at the level of the response rate of these Unruh DeWitt detectors in a wide class of Friedmann spacetimes. In order to carry out this study, we make use of an equivalence that exists between massless scalar fields in FRW spacetimes with massive scalar fields in de Sitter spacetime. Further, we show that while the derivative coupling regulates the divergence appearing in de Sitter spacetime, it does not completely remove them in matter dominated universe. This gives rise to large transitions in the detector which can be used as a probe of setting up of large correlations in late time era of the universe as well. We also apply the results of these otherwise formal analyses to the coupling of hydrogen atoms with gravitational waves. We show that the coupling of hydrogen atoms with gravitational waves takes a form that is similar to derivatively coupled UDW detectors and hence has significant observational implications as a probe of late time revival of quantum correlators.

A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents femtoscope—a python numerical tool based on the finite element method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, femtoscope is showcased with a study of the chameleon fifth force in Earth orbit.

We revisit the box Minkowski model [M. Maliborski, Instability of Flat Space Enclosed in a Cavity, Phys. Rev. Lett. 109, 221101 (2012).] and provide a strong argument that, subject to the Dirichlet boundary condition, it is unstable toward black hole formation for arbitrarily small generic perturbations. Using weakly nonlinear perturbation theory, we derive the resonant system, which compared to systems with the anti–de Sitter asymptotics has extra resonant terms, and study its properties, including conserved quantities. We find that the generic solution of the resonant system becomes singular in finite time. Surprisingly, the additional resonant interactions do not significantly affect the singular evolution. Furthermore, we find that the interaction coefficients take a relatively simple form, making this a particularly attractive toy model of turbulent gravitational instability.

Neutrino self-interactions in a dense neutrino gas can induce collective neutrino flavor conversions. Fast neutrino flavor conversions (FFCs), one of the collective neutrino conversion modes, potentially change the dynamics and observables in core-collapse supernovae and binary neutron star mergers. In cases without neutrino-matter interactions (or collisions), FFCs are essentially energy independent, and, therefore, the single-energy treatment has been used in previous studies. However, neutrino-matter collisions, in general, depend on neutrino energy, suggesting that energy-dependent features may emerge in FFCs with collisions. In this paper, we perform dynamical simulations of FFCs with isoenergetic scatterings (emulating nucleon scatterings) under multienergy treatment. We find that cancellation between in- and outscatterings happens in the high-energy region, which effectively reduces the number of collisions and then affects the FFC dynamics. In fact, the lifetime of FFCs is extended compared to the single-energy case, leading to large flavor conversions. Our result suggests that the multienergy treatment is mandatory to gauge the sensitivity of FFCs to collisions. We also provide a useful quantity to measure the importance of multienergy effects of collisions on FFCs.

The diffuse supernova neutrino background (DSNB) is a powerful future tool to constrain core-collapse explosion mechanisms without observation of a nearby event, and the corresponding signal has been calculated for a variety of collapse models. For Supernova (SN) 1987A, a peculiar double neutrino burst was detected, but models for the double collapse have never been studied in the DSNB context. Here, we fill this gap and compare the DSNB signal expected in the standard collapse (SC) and the double collapse (DC) models in various future detectors, including Hyper-Kamiokande, JUNO, DUNE, and the Large Baksan Neutrino Telescope (LBNT). We calculate the spectra of diffuse neutrinos and antineutrinos in the DC model and determine the rate of registered events as a function of energy of the detected particle, taking into account detector parameters. For each detector, we estimate the corresponding uncertainties and the background and compare the signals expected for the SC and DC models. We conclude that the combination of DUNE and LBNT data will have the highest sensitivity to restrict the DC model in the DSNB.

The bubble nucleation efficiency of low-energy nuclear recoils in superheated liquids plays a crucial role in interpreting results from direct searches for weakly interacting massive particle (WIMP) dark matter. The PICO collaboration presents the results of the efficiencies for bubble nucleation from carbon and fluorine recoils in superheated ${\mathrm{C}}_3{\mathrm{F}}_8$ from calibration data taken with five distinct neutron spectra at various thermodynamic thresholds ranging from 2.1 to 3.9 keV. Instead of assuming any particular functional forms for the nuclear recoil efficiency, a generalized piecewise linear model is proposed with systematic errors included as nuisance parameters to minimize model-introduced uncertainties. A Markov chain Monte Carlo routine is applied to sample the nuclear recoil efficiency for fluorine and carbon at 2.45 and 3.29 keV thermodynamic thresholds simultaneously. The nucleation efficiency for fluorine was found to be $\ge 50\%$ for nuclear recoils of 3.3 keV (3.7 keV) at a thermodynamic Seitz threshold of 2.45 keV (3.29 keV), and for carbon the efficiency was found to be $\ge 50\%$ for recoils of 10.6 keV (11.1 keV) at a threshold of 2.45 keV (3.29 keV). Simulated datasets are used to calculate a p value for the fit, confirming that the model used is compatible with the data. The fit paradigm is also assessed for potential systematic biases, which although small, are corrected for. Additional steps are performed to calculate the expected interaction rates of WIMPs in the PICO-60 detector, a requirement for calculating WIMP exclusion limits.