The baryon mass operator is studied within a combined expansion in $1/N_c$ and perturbative $SU(3)$ flavor symmetry breaking, where $N_c$ denotes the number of color charges. Flavor projection operators are used to classify the baryon operators involved in the expansion, which fall into the flavor representations 1, 8, $10+\overline{10}$, 27, $35+\overline{35}$, and 64. This approach allows one to incorporate up to third-order flavor symmetry breaking in the baryon mass operator in a rigorous and systematic way. Previous work on the subject is considered to validate the approach. A fit to data is performed to evaluate the free parameters in the theory and to produce some numerical values of baryon masses. Results are consistent and reaffirm the striking success of the $1/N_c$ expansion.

We present the first theoretical calculation of nonfactorizable charm-quark loop contributions to the $B_s\to \gamma l^{+}{l}^{-}$ amplitude. We calculate the relevant form factors, $H_{A,V}^{\mathrm{NF}}(k^{\prime 2},k^2)$, and provide convenient parametrizations of our results in the form of fit functions of two variables, $k^{\prime 2}$ and $k^2$, applicable in the region below hadron resonances, $k^{\prime 2}<M_{J/\psi }^2$ and $k^2<M_{\varphi }^2$. We report that factorizable and nonfactorizable charm contributions to the $B_s\to \gamma l^{+}{l}^{-}$ amplitude have opposite signs. To compare the charm and the top contributions, it is convenient to express nonfactorizable charming loop contribution as a nonuniversal (i.e., dependent on the reaction) $q^2$-dependent correction ${\mathrm{\Delta }}^{\mathrm{NF}}{C}_7(q^2)$ to the Wilson coefficient $C_7$. For the $B_s\to \gamma l^{+}{l}^{-}$ amplitude, the correction is found to be positive, ${\mathrm{\Delta }}^{\mathrm{NF}}{C}_7(q^2)/C_7>0$.

Nuclear collisions at sufficiently high energies are expected to produce far-from-equilibrium matter with a high density of gluons at early times. We show gauge condensation, which occurs as a consequence of the large density of gluons. To identify this condensation phenomenon, we construct two local gauge invariant observables that carry the macroscopic zero mode of the gauge condensate. The first order parameter for gauge condensation investigated here is the correlator of the spatial Polyakov loop. We also consider, for the first time, the correlator of the gauge invariant scalar field, associated with the exponent of the Polyakov loop. Using real-time lattice simulations of classical-statistical SU(2) gauge theory, we find gauge condensation on a system-size-dependent timescale $t_{\mathrm{cond}}\sim L^{1/\zeta }$ with a universal scaling exponent $\zeta$. Furthermore, we suggest an effective theory formulation describing the dynamics using one of the order parameters identified. The formation of a condensate at early times may have intriguing implications for the early stages in heavy-ion collisions.

The vectorlike quark model is one of the extensions of the standard model (SM) of particle physics. The simplest version of this model introduces a vectorlike singlet quark which can mix with SM quarks and give rise to new contributions to the flavor-changing decays of the Higgs boson. In this work we first present a systematic analysis of the branching ratios of the decays $H\to b\overline{s},b\overline{d}$ at leading order in the standard model. Our results show that it is challenging to observe these two modes because of their small branching ratios. Then augmenting the SM with a vectorlike singlet top quark, assuming the top partner only mixes with the top quark, complete one-loop contributions are taken into account in the amplitudes. Further results indicate that the branching ratios of the decays $H\to b\overline{s},b\overline{d}$ are sensitive to the mass of the top partner $M_T$ and the mixing effects characterized by $\sin {\theta }_L$. By tuning the values of $M_T$ and $\sin {\theta }_L$, the branching ratios may rise to a level accessible to LHC experiments. Combined with the branching ratios obtained from a probabilistic model, the allowed areas in the $M_T-\sin {\theta }_L$ plane are displayed. Tagging efficiencies and feasibility for detecting $H\to b\overline{s}$ are specifically discussed and we conclude that with large statistics it is promising to discover the $H\to b\overline{s}$ decay at the LHC.

A search for high-mass resonances decaying into a $\tau$-lepton and a neutrino using proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ is presented. The full run 2 data sample corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$ recorded by the ATLAS experiment in the years 2015–2018 is analyzed. The $\tau$-lepton is reconstructed in its hadronic decay modes and the total transverse momentum carried out by neutrinos is inferred from the reconstructed missing transverse momentum. The search for new physics is performed on the transverse mass between the $\tau$-lepton and the missing transverse momentum. No excess of events above the Standard Model expectation is observed and upper exclusion limits are set on the $W^{\prime }\to \tau \nu$ production cross section. Heavy $W^{\prime }$ vector bosons with masses up to 5.0 TeV are excluded at 95% confidence level, assuming that they have the same couplings as the Standard Model $W$ boson. For nonuniversal couplings, $W^{\prime }$ bosons are excluded for masses less than 3.5–5.0 TeV, depending on the model parameters. In addition, model-independent limits on the visible cross section times branching ratio are determined as a function of the lower threshold on the transverse mass of the $\tau$-lepton and missing transverse momentum.

We demonstrate that in a chiral plasma subject to an external magnetic field, the chiral vortical effect can induce a new type of magnetohydrodynamic instability, which we refer to as the chiral magnetovortical instability. This instability arises from the mutual evolution of the magnetic and vortical fields. It can cause a rapid amplification of the magnetic fields by transferring the chirality of the constituent particles to the cross helicity of the plasma.

In the two-dimensional Liouville conformal field theory, correlation functions involving a degenerate field satisfy partial differential equations due to the decoupling of the null descendant field. On the other hand, the instanton partition function of a four-dimensional $\mathcal{N}=2$ supersymmetric theory in the $\mathrm{\Omega }$-background at a special point of the parameter space also satisfies a partial differential equation resulting from the constraints of the gauge field configurations. This partial differential equation can be proved using the nonperturbative Dyson-Schwinger equations. We show for the next-to-simplest case that the partial differential equations obtained from two different perspectives can be identified, thereby confirming an assertion of the Bogomol’nyi-Prasad-Sommerfield/conformal field theory correspondence.

It has been proven that nonlinear electromagnetic fields can result in regular black holes without singularities in the origin. Consequently, even if the event horizon disappears, this spacetime will not lead to the problem of naked singularities but, instead, becomes a regular spacetime. Thus, it is interesting to study the scalar field evolution in nonlinear electromagnetic regular anti–de Sitter spacetimes in order to analyze its stability. In these regular anti–de Sitter spacetimes, the tortoise coordinate transformation $r_{*}$ has an upper and lower limit, respectively, and the effective potential of scalar perturbation diverges at maximum $r_{*}$, so that the wave cannot penetrate this boundary. On the other hand, at the center of the regular spacetime, the value of the effective potential even with $L=0$ does not diverge, so the reflection at the center of the wave is equivalent to the reflection on one side of the wave-spreading medium, resulting in a phenomenon of half-wave loss. It means that the process of scalar perturbations in this spacetime is similar to the standing wave vibrations with fixed boundaries in wave mechanics. We will calculate the scalar field normal modes of oscillation and demonstrate the phenomena of standing waves and half-wave loss of nonlinear electromagnetic regular anti–de Sitter spacetimes.

We compute the vacuum metric generated by a generic rotating object in arbitrary dimensions up to third post-Minkowskian order by computing the classical contribution of scattering amplitudes describing the graviton emission by massive spin-1 particles up to two loops. The solution depends on the mass, angular momenta, and on up to two parameters related to generic quadrupole moments. In $D=4$ spacetime dimensions, we recover the vacuum Hartle-Thorne solution describing a generic spinning object to second order in the angular momentum, of which the Kerr metric is a particular case obtained for a specific mass quadrupole moment dictated by the uniqueness theorem. At the level of the effective action, the case of minimal couplings corresponds to the Kerr black hole, while any other mass quadrupole moment requires nonminimal couplings. In $D>4$, the absence of black-hole uniqueness theorems implies that there are multiple spinning black hole solutions with different topology. Using scattering amplitudes, we find a generic solution depending on the mass, angular momenta, the mass quadrupole moment, and a new stress quadrupole moment which does not exist in $D=4$. As special cases, we recover the Myers-Perry and the single-angular-momentum black ring solutions, to third and first post-Minkowksian order, respectively. Interestingly, at variance with the four-dimensional case, none of these solutions corresponds to the minimal coupling in the effective action. This shows that, from the point of view of scattering amplitudes, black holes are the “simplest” general relativity vacuum solutions only in $D=4$.

We examined the output of a quantum Michelson interferometer incorporating the combined effects of nonlinear optomechanical interaction and time-varying gravitational fields. Our findings indicate a deviation from the standard relationship between the phase shift of the interferometer’s output and the amplitude of gravitational waves. This deviation, a slight offset in direct proportionality, is associated with the gravitational wave memory effect under the conventional settings of interferometer parameters. Furthermore, the results suggest that consecutive gravitational wave memory, or the stochastic gravitational wave memory background (SGWMB), contributes not only to the classical red noise spectrum but also to a quantum red noise spectrum through this new mechanism. This leads to a novel quantum noise limit for interferometers, which may be crucial for higher precision detection system. Our analysis potentially offers a more accurate description of quantum interferometers responding to gravitational waves and applies to other scenarios involving time-varying gravitational fields. It also provides insights and experimental approaches for exploring how to unify the quantum effects of macroscopic objects and gravitation.

The search for subsolar mass primordial black holes (PBHs) poses a challenging problem due to the low signal-to-noise ratio, extended signal duration, and computational cost demands, compared to solar mass binary black hole events. In this paper, we explore the possibility of investigating the mass range between subsolar and planetary masses, which is not accessible using standard matched filtering and continuous wave searches. We propose a systematic approach employing the Viterbi algorithm, a dynamic programming algorithm that identifies the most likely sequence of hidden Markov states given a sequence of observations, to detect signals from small mass PBH binaries. We formulate the methodology, provide the optimal length for short-time Fourier transforms, and estimate sensitivity. Subsequently, we demonstrate the effectiveness of the Viterbi algorithm in identifying signals within mock data containing Gaussian noise. Our approach offers the primary advantage of being agnostic and computationally efficient.

We propose a method to constrain the chameleon dark energy using atom interference in an optical lattice by measuring the acceleration near a glass disk. Since the lattice fixes the positions of the atoms, our method is effective in suppressing the decay of the chameleon field with distance compared to the reported works with free-falling atoms. In addition, we choose a circular glass disk as the source mass, which makes the gravitational effect at close range almost invariant. The fixed atomic position and the symmetry of the source mass reduce the difficulty of studying the systematic errors. At the same acceleration measurement precision, our method is expected to have a larger chameleon parameter exclusion region than the atomic test for usual distances.

In the last few years, there has been significant progress in the development of machine learning methods tailored to astrophysics and cosmology. We have recently applied one of these, namely, the neural network bundle method, to the cosmological scenario. Moreover, we showed that in some cases the computational times of the Bayesian inference process can be reduced. In this paper, we present an improvement to the neural network bundle method that results in a significant reduction of the computational times of the statistical analysis. The novel aspect consists of the use of the neural network bundle method to calculate the luminosity distance of type Ia supernovae, which is usually computed through an integral with numerical methods. In this work, we have applied this improvement to the Hu-Sawicki and Starobinsky $f(R)$ models. We also performed a statistical analysis with data from type Ia supernovae of the $\mathrm{Pantheon}+$ compilation and cosmic chronometers. Another original aspect of this work is the different treatment we provide for the absolute magnitude of type Ia supernovae during the inference process, which results in different estimates of the distortion parameter than the ones obtained in the literature. We show that the statistical analyses carried out with our new method require lower computational times than the ones performed with both the numerical and the neural network method from our previous work. This reduction in time is more significant in the case of a difficult computational problem such as the ones addressed in this work.

Stochastic gravitational-wave (GW) background (SGWB) contains information about the early Universe and astrophysical processes. The recent evidence of SGWB by pulsar timing arrays in the nanohertz band is a breakthrough in the GW astronomy. For ground-based GW detectors, while in data analysis, the SGWB can be masked by loud GW events from compact binary coalescences (CBCs). Assuming a next-generation ground-based GW detector network, we investigate the potential for detecting the astrophysical and cosmological SGWB with non-CBC origins by subtracting recovered foreground signals of loud CBC events. The Fisher Information Matrix (FIM) method is adopted for quick calculation. As an extension of the previous studies, two more essential features are considered. Firstly, we incorporate nonzero aligned or antialigned spin parameters in our waveform model. Because of the inclusion of spins, we obtain significantly more pessimistic results than the previous work, where the residual energy density of foreground is even larger than the original CBC foreground. For the most extreme case, we observe that the subtraction results are approximately 10 times worse for binary black hole events and 20 times worse for binary neutron star events than the scenarios without accounting for spins. The degeneracy between the spin parameters and the symmetric mass ratio is strong in the parameter estimation process, and it contributes most to the imperfect foreground subtraction. Secondly, in this work, extreme CBC events with condition numbers of FIMs $c_{\mathrm{\Gamma }}>{10}^{15}$ are preserved. The impacts of these extreme events on foreground subtraction are discussed. Our results have important implications for assessing the detectability of SGWB from non-CBC origins for ground-based GW detectors.

In this paper, we focus on the effect of mass-transfer between compact binaries like neutron star–neutron star systems and neutron star–white dwarf systems on gravitational waves (GWs). We adopt the mass quadrupole formula with 2.5 order post-Newtonian approximation to calculate the GW radiation and the orbital evolution. After a reasonable discussion of astrophysical processes concerning our scenario, two kinds of mass-transfer models are applied here. One is the mass overflow of the atmosphere, where the companion star orbits into the primary’s Roche limit and its atmosphere overflows into the common envelope. The other one is the tidal disruption of the core, which is viewed as incompressible fluid towards the primary star, and in the near region branches into an accretion disk and direct accretion flow. Viewing this envelope and as a background, the GW of its spin can be calculated as a rotating nonspherically symmetric star. We eventually obtain the corrected gravitational waveform templates for different initial states in the inspiral phase.

Primordial black holes (PBHs), if they exist, may collide with and be captured by neutron stars. We adopt a relativistic point-mass approximation to study this capture, the subsequent confinement of the PBH of mass $m$ inside the neutron star of mass $M_{*}\gg m$, and the PBH’s growth by accretion of stellar material. Building on earlier treatments we systematically study the capture, confinement, and accretion process, characterize the emitted quasiperiodic continuous gravitational-wave signal, track the evolution of the PBH’s orbital parameters, and compare the effects of different choices for the prescription of the dissipative forces. Our point-mass treatment here is applicable in the limit of small PBH masses, for which its effects on the neutron star can be ignored.

There is a significant interest in testing quantum entanglement and Bell inequality violation in high-energy experiments. Since the analyses in high-energy experiments are performed with events statistically averaged over phase space, the states used to determine observables depend on the choice of coordinates through an event-dependent basis and are thus not genuine quantum states, but rather “fictitious states.” We find that the basis which diagonalizes the spin-spin correlations is optimal for constructing fictitious states to test the violation of Bell’s inequality. This result is applied directly to the bipartite qubit system of a top and antitop produced at a hadron collider. We show that the beam axis is the optimal basis choice near the $t\overline{t}$ threshold production for measuring Bell inequality violation, while at high transverse momentum the basis that aligns along the momentum direction of the top is optimal.

In this article, we analyze the role of an external electric field, in the weak field approximation, on $\pi \text{−}\pi$ scattering lengths. The discussion is presented in the frame of the linear sigma model. To achieve this, we take into account all one-loop corrections in the $s$, $t$, and $u$ channels associated with the insertion of a Schwinger propagator for charged pions, focusing on the region characterized by small values of the electric field. Furthermore, one of the novelties of our work is the explicit calculation of box diagrams, which were previously overlooked in discussions regarding magnetic corrections. It turns out that the electric field corrections have an opposite effect with respect to magnetic corrections calculated previously in the literature.