A major result of the effective string theory (EST) description of confinement is the so-called “low-energy universality”, which states that the first few terms of the large distance expansion of any EST are universal and coincide with those of the Nambu-Goto action. Going beyond this approximation is one of the most interesting open problems in the EST. In the higher-order terms beyond Nambu-Goto several important pieces of physical information are encoded, which could improve our understanding of the physical mechanisms behind confinement and of the physical degrees of freedoms which originate the EST. In this paper we evaluate numerically the first two of these corrections in the case of the three-dimensional gauge Ising model. The first of them turns out to be negative; ${\gamma }_3=-0.00048(4)$, similar (but not equal) to the one recently measured in the $SU(2)$ Yang-Mills theory in three dimensions and compatible with the bootstrap bound ${\gamma }_3\ge -\frac{1}{768}$.

We derive the quantum kinetic theory for massive fermions with collision terms and self-energy corrections based on quantum field theory. We adopt an effective power-counting scheme with $\hslash$ expansion to obtain the leading-order perturbative solutions of the vector and axial Wigner functions and the corresponding kinetic equations. We observe that both the on-shell relation and the structure of Wigner functions, along with the kinetic equations, are modified due to the presence of self-energies and their spacetime gradients. We further apply our formalism to investigate the spin polarization phenomena in relativistic heavy ion collisions and derive the modification to the spin polarization spectrum of massive quarks. We find that the gradient of vector self-energy plays a similar role to the background electromagnetic fields, which induces a more dominant contribution than the collisional effects by a naive power counting in the gradient expansion and weak coupling. Our findings could further modify the spin polarization of strange quarks and the spin alignment of $\varphi$ mesons beyond local thermal equilibrium.

Weakly supervised methods have emerged as a powerful tool for model-agnostic anomaly detection at the Large Hadron Collider (LHC). While these methods have shown remarkable performance on specific signatures such as dijet resonances, their application in a more model-agnostic manner requires dealing with a larger number of potentially noisy input features. In this paper, we show that using boosted decision trees as classifiers in weakly supervised anomaly detection gives superior performance compared to deep neural networks. Boosted decision trees are well known for their effectiveness in tabular data analysis. Our results show that they not only offer significantly faster training and evaluation times, but they are also robust to a large number of noisy input features. By using advanced gradient boosted decision trees in combination with ensembling techniques and an extended set of features, we significantly improve the performance of weakly supervised methods for anomaly detection at the LHC. This advance is a crucial step toward a more model-agnostic search for new physics.

We perform an analysis of triangle- and box-loop contributions to the generalized potential in the scattering of Goldstone bosons off the $J^P=0^{-}$ and $1^{-}$ charmed mesons. Particular emphasis is put on the use of on-shell mass parameters in such contributions in terms of a renormalization scheme that ensures the absence of power-counting violating terms. This is achieved with a systematically extended set of Passarino-Veltman basis functions that leads to manifest power-counting conserving one-loop expressions and avoids the occurrence of superficial kinematical singularities. Compact expressions to chiral order three and four are presented that are particularly useful in coding such coupled-channel systems. Our formal results are generic and prepare analogous computations for other systems, like meson-baryon scattering from the chiral Lagrangian.

We investigate the twist-3 generalized parton distributions (GPDs) for the valence quarks of the proton within the basis light-front quantization (BLFQ) framework. We first solve for the mass spectra and light-front waved functions (LFWFs) in the leading Fock sector using an effective Hamiltonian. Using the LFWFs we then calculate the twist-3 GPDs via the overlap representation. By taking the forward limit, we also get the twist-3 parton distribution functions (PDFs), and discuss their properties. Our prediction for the twist-3 scalar PDF agrees well with the CLAS experimental extractions.

Possibilities of the formation of the pion-sigma meson field vortices in a rotating empty vessel (in vacuum) and in the pion-sigma Bose-Einstein condensates at a dynamically fixed particle number are studied within the linear $\sigma$ model at zero temperature. The charged $\sigma {\pi }^{\pm }$ and neutral $\sigma {\pi }^0$ complex field Ansätze (models 1 and 2) are studied. First it is analyzed which of these configurations is energetically favorable in case of the system at rest. Then conditions are found at which a chiral field storm can arise in a rotating empty vessel. In model 1, an important role played by the electric field is demonstrated. Its appearance may allow for formation of a supervortex (vortex with a large angular momentum) in case of the empty vessel rotating with an overcritical angular velocity. Influence of magnetic field is also studied. Field configurations in presence and absence of the meson self-interaction are found in both models. Then it is shown that the description of the charged (in model 1) and neutral (in model 2) rotating pion-sigma Bose-Einstein condensates is analogous to that for the Bose-Einstein condensates in cold atomic gases. Various field configurations such as vortex lines, rings and spirals are discussed. Conditions for existence of the rigid-body rotation of the vortex lattice are then analyzed. Observational effects for vortex fields in rotating vessels, energetic heavy-ion collisions and in rotating superheavy nuclei and nuclearites are discussed.

The process $e^{+}{e}^{-}\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ is studied from threshold up to $3.04\mathrm{GeV}/c^2$ via the initial-state radiation technique using data with an integrated luminosity of $12.0{\mathrm{fb}}^{-1}$, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of $\mathrm{\Sigma }$ are measured in eleven ${\mathrm{\Sigma }}^{+}$${\overline{\mathrm{\Sigma }}}^{-}$ invariant mass intervals from threshold to $3.04\mathrm{GeV}/c^2$. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays $J/\psi \to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and $\psi (3686)\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ are determined and the obtained results are consistent with the previous results of BESIII.

We study the penguin over tree ratio in $D\to \pi \pi$ decays. This ratio can serve as a probe for rescattering effects. Assuming the Standard Model and in the isospin limit, we derive expressions that relate both the magnitude and the phase of this ratio to direct $CP$ asymmetries and branching fractions. We find that the current data suggest that rescattering is large. A dedicated experimental analysis with current and future data will be able to significantly reduce the errors on these determinations, and enable us to check if indeed there is significant rescattering in $D\to \pi \pi$ decays.

Recent attempts to fully resolve the Hubble tension from early dark energy models seem to favor a primordial Harrison-Zeldovich universe with its scalar spectrum being extremely scale invariant. Restoring the Harrison-Zeldovich spectrum within the single-field inflationary paradigm appears to be infeasible, turning to the multifield approach from either curvaton or waterfall models. In this Letter, we successfully align with the Harrison-Zeldovich spectrum within a single-field chaotic inflation by a nonminimal derivative coupling, and the previously disfavored chaotic potential by $\mathrm{Planck}+\mathrm{BICEP}/\mathrm{Keck}$ data in the standard $\mathrm{\Lambda }$-cold-dark-matter model now returns back to the scope of future polarization observations of the cosmic microwave background.

Ab initio Monte Carlo simulations of strongly interacting fermionic systems are plagued by the fermion sign problem, making the nonperturbative study of many interesting regimes of dense quantum matter, or of theories of odd numbers of fermion flavors, challenging. Moreover, typical fermion algorithms require the computation (or sampling) of the fermion determinant. We focus instead on the meron cluster algorithm, which can solve the fermion sign problem in a class of models without involving the determinant. We develop and benchmark new meron algorithms to simulate fermions coupled to ${\mathbb{Z}}_2$ and $U(1)$ gauge fields in the presence of appropriate four-fermi interactions. Such algorithms can be used to uncover potential exotic properties of matter, particularly relevant for quantum simulator experiments. We demonstrate the emergence of the Gauss’ law at low temperatures for a $U(1)$ model in $(1+1)\mathrm{D}$.

A compact body in orbit about a black hole loses orbital energy and angular momentum through radiation-reaction processes, inspiralling toward the black hole until a final plunge. Here we consider a scenario with a charged compact body in which fluxes of electromagnetic radiation drive this inspiral. We calculate trajectories in the $(p,e)$ plane for inspirals in the equatorial plane of a rotating black hole within the adiabatic (orbital-averaged-dissipative) approximation. We make comparisons with a nonrelativistic Keplerian approximation based on the Abraham-Lorentz force law, and with standard gravitational-wave driven scenarios. We find that EM-driven inspirals are less efficiently circularized (i.e. orbits remain more eccentric at the point of plunge) than their gravitational counterparts, and we quantify the effect of black hole spin.

A set of tidal Love numbers quantifies tidal deformation of compact objects and is a detectable imprint in gravitational waves from inspiraling binary systems. The measurement of black hole Love numbers allows us to test strong-field gravity. In this paper, we present a parametrized formalism to compute the Love numbers of static and spherically symmetric black hole backgrounds, connecting the underlying equations of a given theory with detectable quantities in gravitational-wave observations in a theory-agnostic way. With this formalism, we compute the Love numbers in several systems. We further classify black hole Love numbers according to whether they vanish, are nonzero, or are “running” (scale- dependent), in theories or backgrounds that deviate perturbatively from the general relativity values. The construction relies on static linear perturbations and scattering theory. Our analytic and numerical results are in excellent agreement. As a side result, we show how to use Chandrasekhar’s relations to relate basis of even parity to odd parity.

We study covariant models for vacuum spherical gravity within a canonical setting. Starting from a general ansatz, we derive the most general family of Hamiltonian constraints that are quadratic in first-order and linear in second-order spatial derivatives of the triad variables, and obey certain specific covariance conditions. These conditions ensure that the dynamics generated by such family univocally defines a spacetime geometry, independently of gauge or coordinates choices. This analysis generalizes the Hamiltonian constraint of general relativity, though keeping intact the covariance of the theory, and leads to a rich variety of new geometries. We find that the resulting geometries depend on seven free functions of one scalar variable, and we study their generic features. By construction, there are no propagating degrees of freedom in the theory. However, we also show that it is possible to add matter to the system by simply following the usual minimal-coupling prescription, which leads to novel models to describe dynamical scenarios.

A remarkable double-copy relation of Einstein gravity to QCD in Regge asymptotics is ${\mathrm{\Gamma }}^{\mu \nu }=\frac{1}{2}{C}^{\mu }{C}^{\nu }-\frac{1}{2}{N}^{\mu }{N}^{\nu }$, where ${\mathrm{\Gamma }}^{\mu \nu }$ is the gravitational Lipatov vertex in the $2\to 3$ graviton scattering amplitude, $C^{\mu }$ its Yang-Mills counterpart, and $N^{\mu }$ the QED bremsstrahlung vertex. In QCD, the Lipatov vertex is a fundamental building block of the BFKL equation describing the $2\to N$ scattering of gluons at high energies. Likewise, the gravitational Lipatov vertex is a key ingredient in a 2D effective field theory framework describing trans-Planckian $2\to N$ graviton scattering. We construct a quantitative correspondence between a semiclassical Yang-Mills framework for radiation in gluon shockwave collisions and its counterpart in general relativity. In particular, we demonstrate the Lipatov double copy in a dilute-dilute approximation corresponding to $R_{S,L}$, $R_{S,H}\ll b$, where $R_{S,L}$, $R_{S,H}$ are the respective emergent Schwarzchild radii generated in shockwave collisions and $b$ is the impact parameter. We outline extensions of the correspondence developed here to the dilute-dense computation of gravitational wave radiation in the close vicinity of one of the black holes, the construction of graviton propagators in the shockwave background, and a renormalization group approach to compute $2\to N$ amplitudes that incorporates graviton Reggeization and coherent graviton multiple scattering.

In the primordial plasma, at temperatures above the scale of electroweak symmetry breaking, the presence of chiral asymmetries is expected to induce the development of helical hypermagnetic fields through the phenomenon of chiral plasma instability. It results in magnetohydrodynamic turbulence due to the high conductivity and low viscosity and sources gravitational waves that survive in the universe today as a stochastic polarized gravitational wave background. In this article, we show that this scenario only relies on Standard Model physics, and therefore the observable signatures, namely the relic magnetic field and gravitational background, are linked to a single parameter controlling the initial chiral asymmetry. We estimate the magnetic field and gravitational wave spectra, and validate these estimates with 3D numerical simulations.

We place observational constraints on a dark energy (DE) model in which a quintessence scalar field $\varphi$ is coupled to dark matter (DM) through momentum and energy exchanges. The momentum transfer is weighed by an interaction between the field derivative and DM four velocity with a coupling constant $\beta$, whereas the energy exchange is characterized by an exponential scalar-field coupling to the DM density with a coupling constant $Q$. A positive coupling $\beta$ leads to the suppression for the growth of DM density perturbations at low redshifts, whose property offers a possibility for resolving the ${\sigma }_8$ tension problem. A negative coupling $Q$ gives rise to a $\varphi$-matter-dominated epoch, whose presence can reduce the sound horizon around the cosmic microwave background (CMB) decoupling epoch. Using the data of the Planck 2018, 12th Sloan Digital Sky Survey, Phantheon supernovae samples, and 1-year dark energy survey, we find that the two couplings are constrained to be $\beta =0.332_{-0.237}^{+1.246}$ and $Q=-0.0312_{-0.0085}^{+0.0312}$ at a 68% confidence level (CL). Thus, there is an interesting observational signature of the momentum exchange ($\beta \ne 0$) between DE and DM, with a peak of the probability distribution of the energy transfer coupling at $Q<0$.

The question that continues to hinge the interrelation between cosmology and thermodynamics is broadly described as—What is the form of horizon entropy that links the Friedmann equations for a “general” gravity theory with the underlying thermodynamics of the apparent horizon? The answer to this question was known only for Einstein’s gravity and for ($n+1$) dimensional Gauss-Bonnet gravity theory, but not for a general modified theory of gravity [for instance, the $F(R)$ gravity]. In the present work, we take this issue and determine a general form of entropy that connects the Friedmann equations for any gravity theory with the apparent horizon thermodynamics given by $TdS=-dE+WdV$ [the symbols have their usual meaning in the context of entropic cosmology and $W=(\rho -p)/2$ is the work density of the matter fields represented by $\rho$ and $p$ as the energy density and the pressure, respectively]. Using such generalized entropy, we find the respective entropies for several modified theories of gravity [including the $F(R)$ gravity]. Further, it turns out that besides the above-mentioned question, the thermodynamic law $TdS=-dE+WdV$ itself has some serious difficulties for certain values of $\omega$ [the equations of state (EOSs) of the matter field]. Thus we propose a modified thermodynamic law of apparent horizon, given by $TdS=-dE+\rho dV$, that is interestingly free from such difficulties. The modified law proves to be valid for all EOSs of the matter field and thus is considered to be more general compared to the previous one which, however, is a limiting case of the modified law for $p=-\rho$. Based on such modified thermodynamics, we further determine a generalized entropy that can provide the Friedmann equations of any general gravity theory for all values of EOSs of the matter field. The further implications are discussed.

We report results from an all-sky search of the LIGO data from the third LIGO-Virgo-KAGRA run (O3) for continuous gravitational waves from isolated neutron stars in the frequency band [30, 150] Hz and spindown range of $[-1\times {10}^{-8},+1\times {10}^{-9}]\mathrm{Hz}/\mathrm{s}$. This search builds upon a previous analysis of the first half of the O3 data using the same powerflux pipeline. We search more deeply here by using the full O3 data and by using loose coherence in the initial stage with fully coherent combination of LIGO Hanford (H1) and LIGO Livingston (L1) data, while limiting the frequency band searched and excluding narrow, highly disturbed spectral bands. We detect no signal and set strict frequentist upper limits on circularly polarized and on linearly polarized wave amplitudes, in addition to estimating population-averaged upper limits. The lowest upper limit obtained for circular polarization is $\sim 4.5\times {10}^{-26}$, and the lowest linear polarization limit is $\sim 1.3\times {10}^{-25}$ (both near 144 Hz). The lowest estimated population-averaged upper limit is $\sim 1.0\times {10}^{-25}$. In the frequency band and spindown range searched here, these limits improve upon the O3a powerflux search by a median factor of $\sim 1.4$ and upon the best previous limits obtained for the full O3 data by a median factor of $\sim 1.1$.

We consider collective Thomson scattering of an incident X-mode wave (with the electric vector perpendicular to the background magnetic field) in magnetized electron and positron pair plasma. The collective effects do not exactly cancel out in contrast to the nonmagnetized case. Still, the cross section is comparable to the noncollective one, with the same suppression by the square of the cyclotron frequency in a strong magnetic field. The comparable cross section holds even though the net current is nearly zero from the drift motion of electrons and positrons. The plasma response does not also affect the cross section so much. The spectrum of the scattered wave in finite temperature plasma peaks at cyclotron overtones. Assuming that these results are applicable, we also estimate induced Compton scattering in strongly magnetized pair plasma. Implications for pulsars and fast radio bursts are discussed.