We investigate the $K\mathrm{\Lambda }$ strong interaction dynamics around the energy region of $N^{*}(1535)$ resonance through femtoscopic correlation functions within the Koonin-Pratt formalism, where coupled-channel effects of $\pi N$, $K\mathrm{\Lambda }$, $K\mathrm{\Sigma }$ and $\eta N$ channels are taken into account, by means of which the $N^{*}(1535)$ resonance can be dynamically generated in the chiral unitary approach. Two-body scattering amplitudes are calculated using the chiral unitary approach, and the corresponding wave functions and correlation functions are obtained. Our analysis shows that the $\pi N$ channel becomes important to the $K^{+}\mathrm{\Lambda }$ correlation function through coupled channel effects, even if its mass threshold is far from the energy region of the $N^{*}(1535)$. Furthermore, with the picture that the $N^{*}(1535)$ is a dynamically generated state, we can get a good reproduction of the experimental data on the $K^{+}\mathrm{\Lambda }$ correlation function. This work establishes femtoscopic correlation functions as a sensitive probe for coupled-channel dynamics and validates the Koonin-Pratt framework in multichannel hadronic systems, offering critical insights into some exotic hadron states and strong interaction mechanisms.

A new first-order theory of relativistic dissipation has been recently proposed, where viscous effects are incorporated using the traditional Navier-Stokes framework. Its main novelty is the avoidance of dynamical instabilities by allowing different observers to use equations that are not related by exact Lorentz transformations. In this work, we explore the implications of this noncovariance in depth. In particular, we discuss how predictions differ between observers moving at nearly luminal speeds relative to each other. We find that all disagreements stem from the relativity of simultaneity, which introduces frame-dependent anisotropic delays in the diffusive process. These anisotropies significantly limit the applicability of the equation used by observers who move very fast relative to the medium. However, the magnitude of the related error remains finite at infinite Lorentz factors, meaning that it is possible to find a regime where all observers agree on the outcome of experiments.

A novel contribution to off forward, exclusive vector quarkonium production, ${\gamma }^{(*)}+p\to V+p$, at high energy is derived which corresponds to a $t$-channel exchange of a Balitsky-Fadin-Kuraev-Lipatov (BFKL) hard Pomeron, with a helicity flip of the proton. This “spin-dependent BFKL Pomeron” is required in a consistent expansion in powers of the momentum transfer $t\approx -{\mathbf{\Delta }}_{\perp }^2$ beyond first order. The spin-dependent Pomeron violates $s$-channel helicity conservation at $\mathcal{O}({\mathrm{\Delta }}_{\perp }^2)$, and beyond. Expanding to leading twist only, it corresponds to generalized parton distributions $E_g(x,t)$ for vanishing skewness. We derive explicit expressions for the eikonal BFKL amplitudes, to all orders in dipole size times momentum transfer, for all helicity configurations of the particles in the initial and final states. We also provide numerical estimates of the helicity flip two gluon exchange amplitude at moderate $x$ from a light cone quark model of the proton. The spin dependent BFKL Pomeron could, in principle, be discovered via double spin asymmetries in $e+p\to e+p+J/\psi$ with a transversely polarized proton and longitudinally polarized electron in the initial state.

In this study, we calculate the screening masses of 40 spin-zero meson and diquark states composed of light, heavy, and heavy-light quarks, within a symmetry-preserving framework based on Dyson-Schwinger equations and a vector $\times$ vector contact interaction. This effective interaction reproduces hadron static properties at $T=0\mathrm{MeV}$ that are in close agreement with experimental data and results from more sophisticated interaction kernels. Our analysis reveals that, at temperatures above the critical temperature, the dressed quark masses of the lightest mesons converge toward their respective current quark masses. Our work extends this study up to $T=500\mathrm{MeV}$. Furthermore, we demonstrate that the screening masses of meson parity partners become degenerate above a characteristic temperature, a phenomenon that is likewise reflected in the thermal evolution of their associated Bethe-Salpeter amplitudes, providing robust evidence for chiral symmetry restoration. A similar trend is observed for scalar and pseudoscalar diquarks, whose screening masses also converge at high temperatures. As a consequence, these diquarks shall contribute equally to the baryon screening masses in the high-temperature regime. Wherever results from other approaches are available, we perform direct comparisons and observe consistency with our findings.

Motivated by the recent $CP$ violation observation, we investigate the $CP$ violation of $b$-baryon charmless four-body decays under the U-spin symmetry. However, we find that only U-spin symmetry cannot provide effective predictions, particularly for ${\mathrm{\Lambda }}_b$ decays. For giving more useful predictions, we also give a simple dynamic analysis. By counting the power ($\lambda =\sqrt{\frac{{\mathrm{\Lambda }}_{\mathrm{QCD}}}{m_b}}$) of each topological diagram, we find that for the specific decay $B_b^2\to R(B_1^2{M}^2{M}^{\overline{2}})M^2$, only one U-spin amplitude can contribute in the leading power, while for $B_b^2\to R(B_1^2{M}^2)R(M^{\overline{2}}{M}^2)$, only two U-spin amplitudes can contribute in this leading power. Then the most effective prediction can be given as $$A_{CP}^{\mathrm{dir}}({\mathrm{\Lambda }}_b^0\to R(p{\pi }^{-}{\pi }^{+}){\pi }^{-})=(-12.99\pm 2.83\pm 2.59\pm 0.65)\%.$$Considering the ${\mathrm{\Lambda }}_b$ can effectively be produced in LHCb, we strongly encourage a more precise experimental investigation of it.

We continue the study of 2D gravity—“matrix model” duality on the example of a $(2,2p+1)$ minimal string. We propose a reformulation of the duality, related to a more conventional one by “$x\text{−}y$ swap” in the language of topological recursion. This formulation elucidates some conceptual and technical difficulties in the dictionary of the duality and relation to other examples. In particular, it allows to circumvent the necessity to use “resonance transformations,” which were previously introduced to match the world sheet and “matrix model” correlators, and the expressions for minimal string amplitudes in this approach are reminiscent of the ones obtained recently for “complex Liouville string” theory. Using this new approach, we also formulate a conjecture on how one can compute amplitudes with operators other than tachyons in the dual theory.

We investigate the upper bound of the Lyapunov exponent for a charged particle in the Gibbons-Maeda-Garfinkle-Horowitz-Strominger-AdS (GMGHS-AdS) and Kerr-Sen-AdS black hole backgrounds, which originate from the low-energy effective actions of heterotic string theory and gauged supergravity. We analyze the Lyapunov exponent near the unstable orbit to examine possible violations of the bound. Our results indicate that the bound is sensitive to the signs and magnitudes of the charges, angular momentum of the particle, black hole spin, and negative cosmological constant. The violations are pronounced in the extremal or near-extremal regime. Numerical analysis supports the analytical predictions and highlights the interplay between the string-inspired black hole and the charged particle.

In the framework of general relativity, dark energy was proposed to explain the cosmic acceleration. A pivotal inquiry in cosmology is to determine whether dark energy is the cosmological constant and, if not, the challenge lies in constraining how it evolves with time. In this paper, we utilize the latest observational data to constrain some typical dark energy models and make a comparison for them according to their capabilities of fitting the current data. Our study is confined to late-Universe observations, including the baryon acoustic oscillation, type Ia supernova, cosmic chronometer, and strong gravitational lensing time delay data. We employ the Akaike information criterion (AIC), deviance information criterion (DIC), and Bayesian information criterion (BIC) to assess the worth of models. The AIC and DIC analyses indicate that all dark energy models outperform the $\mathrm{\Lambda }\mathrm{CDM}$ model. However, the BIC analysis leaves room for $\mathrm{\Lambda }\mathrm{CDM}$ due to its heavier penalty on the model complexity. Compared to $\mathrm{\Lambda }\mathrm{CDM}$, most dark energy models are robustly supported by AIC and DIC while being explicitly disfavored by BIC. The models that are robustly favored by AIC and DIC and not explicitly disfavored by BIC include the $w\mathrm{CDM}$, interacting dark energy, and Ricci dark energy models. Furthermore, we observe that an alternative modified gravity model exhibits superior performance when compared with $\mathrm{\Lambda }\mathrm{CDM}$ across all information criteria.

Understanding the postmerger evolution of a binary neutron star merger (BNSM) requires accurate modeling of neutrino transport and microphysics including neutrino flavor conversions. Many previous studies have suggested that fast flavor instability (FFI) and collisional flavor instability (CFI) pervade inner regions of the BNSM remnant, and they could impact on fluid dynamics and r-process nucleosynthesis. In this work, we reexamine prospects of the occurrences of FFI and CFI using Boltzmann neutrino transport, assuming a frozen fluid background obtained from a numerical relativity simulation of BNSM. We pay special attention to a case involving a long-lived ($>1\mathrm{s}$) hypermassive neutron star (HMNS). Apart from confirming the claim that these flavor instabilities can occur in BNSM remnants, some new insights are revealed. We identify multiple mechanisms responsible for generating electron-neutrino lepton number (ELN) angular crossings corresponding to a key indicator of FFI onset, which differ notably from those in black hole (BH) accretion disk systems. We argue that the appearance of positive chemical potential of electron-type neutrinos plays important roles in generating ELN angular crossings. For CFI, their growth rates are generally lower than FFI, but they can persistently occur in most of the accretion disk up to $\sim 1\mathrm{s}$. We also find that neglecting contributions of heavy-leptonic neutrinos results in overestimating the growth rate and area of unstable regions of CFI. Our result suggests that FFI (CFI) tends to occur transiently (persistently) and locally (widespread in the disk), and FFI is more sensitive to the central compact object (HMNS or BH) than CFI, though more self-consistent simulations that incorporate the effects of flavor conversions are needed to confirm these claims.

Using the Zubarev’s nonequilibrium statistical operator formalism, we derive the second-order expression for the dissipative tensors in relativistic spin hydrodynamics, viz. rotational stress tensor (${\tau }_{\mu \nu }$), boost heat vector ($q_{\mu }$), shear stress tensor (${\pi }_{\mu \nu }$), and bulk viscous pressure ($\mathrm{\Pi }$). The first two (${\tau }_{\mu \nu }$ and $q_{\mu }$) emerge due to the inclusion of the antisymmetric part in the energy-momentum tensor, which, in turn, governs the conservation of spin angular momentum (${\mathrm{\Sigma }}^{\alpha \mu \nu }$). As a result, new thermodynamic forces, generated due to the antisymmetric part of $T_{\mu \nu }$, contain the spin chemical potential. In this work, we have also taken the spin density ($S^{\mu \nu }$) as an independent thermodynamic variable, in addition to the energy density and particle density, thereby resulting in two novel transport coefficients given by the correlation between spin density tensor and rotational stress tensor and vice versa. Additionally, the newly found terms in ${\pi }_{\mu \nu }$ and $\mathrm{\Pi }$ are the artifacts of the new thermodynamic forces that arise due to the antisymmetric part of $T^{\mu \nu }$. Finally, we have derived the evolution equations for the aforesaid tensors: ${\tau }_{\mu \nu }$, $q_{\mu }$, ${\pi }_{\mu \nu }$, and $\mathrm{\Pi }$.

We perform a numerical analysis of the massive Schwinger model in the presence of a background electric field. Using the Density Matrix Renormalization Group approach, we efficiently compute the spectrum of the Schwinger model on a staggered lattice with up to 3000 qubits. As a result, we achieve a precise computation of the critical mass of the massive Schwinger model to five digits using four different “criticality criteria,” observing perfect agreement among them Additionally, we discuss the effect of a four-fermion operator deformation of the Schwinger model and compute the critical mass for various values of the deformation parameter.

We complete the construction of canonical differential equations (DEs) for all families of Feynman integrals appearing in the two-loop leading-color QCD amplitude for top-pair production in association with a jet at hadron colliders. This allows us to obtain analytic results for all required Feynman integrals in terms of iterated integrals with closed-form kernels. To achieve this, we study the two-loop five-point integral family for which canonical DEs were previously unavailable due to the appearance of elliptic functions and nested square roots. In addition to marking a significant step toward next-to-next-to-leading-order QCD predictions for a high-priority LHC process, this is the first time that canonical DEs are obtained for Feynman integrals where elliptic functions appear in conjunction with the high algebraic complexity of a process with more than four particles. Our results also reveal a number of new interesting analytic features, such as a “duplet” structure that generalizes the even/odd parity of square roots to nested square roots.

We study the Krylov state complexity of the Sachdev-Ye-Kitaev (SYK) model for $N\le 28$ Majorana fermions with $q$-body fermion interaction with $q=4$, 6, 8 for a range of sparse parameter $k$ that controls the number of remaining terms in the original SYK model after sparsification. The critical value of $k$ below which the model ceases to be holographic, denoted $k_c$, has been subject of several recent investigations. Using Krylov complexity as a probe, we find that the peak value of complexity does not change as we increase $k$ beyond $k\ge k_{\min }$ at large temperatures. We argue that this behavior is related to the change in the holographic nature of the Hamiltonian in the sparse SYK-type models such that the model is holographic for all $k\ge k_{\min }\approx k_c$. Our results provide a novel way to determine $k_c$ in SYK-type models.

We compute the four-photon ($F^4$) operators generated by loops of charged particles of spin 0, $\frac{1}{2}$, 1 in the presence of gravity and in any spacetime dimension $d$. To this end, we expand the one-loop effective action via the heat kernel coefficients, which capture both the gravity-induced renormalization of the $F^4$ operators and the low-energy Einstein-Maxwell effective field theory (EFT) produced by massive charged particles. We set positivity bounds on the $F^4$ operators using standard arguments from extremal black holes (for $d\ge 4$) and from infrared (IR) consistency of four-photon scattering (for $d\ge 3$). We find that both approaches yield nearly equivalent results, even though in the amplitudes we discard the graviton $t$-channel pole and use the vanishing of the Gauss-Bonnet term at quadratic order for any $d$. The positivity bounds constrain the charge-to-mass ratio of the heavy particles. If the Planckian $F^4$ operators are sufficiently small or negative, such bounds produce a version of the $d$-dimensional weak gravity conjecture (WGC) in most, but not all, dimensions. In the special case of $d=6$, the gravity-induced beta functions of $F^4$ operators from charged particles of any spin are positive, leading to WGC-like bounds with a logarithmic enhancement. In $d=9$, 10, the WGC fails to guarantee extremal black hole decay in the infrared EFT, thereby requiring the existence of sufficiently large Planckian $F^4$ operators.

We elaborate on the resurgence analysis on the $T\overline{T}$-deformed 2D conformal field theory (CFT). Writing the deformed partition function as an infinite series in the deformation parameter $\lambda$, we develop efficient analytical methods to compute high-order terms of the $\lambda$-series. Based on the asymptotic behavior of the large-order perturbative series, we show that the $\lambda$-series is asymptotic and extract nonperturbative contributions by resurgence. This paper extends a previous Letter of the same authors to interacting rational CFTs, with Lee-Yang CFT as a concrete example. We also discuss possible implications of the resurgence results on holography.

We present a nonperturbative quantization of gravitational null initial data. Our starting point is the characteristic null initial problem for tetradic gravity with a parity-odd Holst term in the bulk. After a basic review about the resulting Carrollian boundary field theory, we introduce a specific class of impulsive radiative data. This class is defined for a certain choice of relational clock. With respect to this clock, the shear of the null congruence that generates the boundary follows the profile of a step function. The angular dependence is arbitrary. Next, we solve the residual constraints, which are the Raychaudhuri equation and a Carrollian transport equation for an $SL(2,\mathbb{R})$ holonomy. We show that the resulting submanifold in phase space is symplectic. Along each null generator, we end up with a simple mechanical system. The quantization of this system is straightforward. Our basic strategy is to start from an auxiliary Hilbert space with constraints. The physical Hilbert space is the kernel of a constraint, which is a combination of ladder operators. The constraint and its Hermitian conjugate are second-class. Solving the constraint amounts to imposing a simple recurrence relation for physical states. On the resulting physical Hilbert space, the $SL(2,\mathbb{R})$ Casimir is a Dirac observable. This observable determines the spectrum of the two radiative modes. Another class of Dirac observables is given by the cross-sectional area densities at the initial and final cuts of the null surface. The resulting area spectrum is discrete, which agrees with earlier results on this topic.

Many searches for continuous gravitational waves face significant computational challenges due to the need to explore large parameter spaces characterized by unknown parameters. Parameter-space metrics are used to predict the relative loss of signal power when the searched parameters differ from the true signal parameters. In this paper, we present generalized parameter-space metrics for the $\mathcal{F}$-statistic (a detection statistic used in many searches) that improve upon previous idealized metrics by incorporating realistic effects such as data gaps and varying noise floors. We derive a new marginalized $\mathcal{F}$-statistic metric that is more accurate than the previous averaged $\mathcal{F}$-statistic metric, especially for short coherent segments. We also derive a more accurate semicoherent metric that properly accounts for the signal-power variability over segments. We provide numerical tests illustrating that the new generalized metrics provide more accurate mismatch predictions than previous expressions. More accurate metrics can result in a reduced number of templates needed for a given search, a feature that could improve the sensitivity of future searches.

The measurement of orbital eccentricity in gravitational-wave (GW) signals will provide unique insights into the astrophysical origin of binary systems, while ignoring eccentricity in waveform models could introduce significant biases in parameter estimation and tests of general relativity. Upcoming LIGO-Virgo-KAGRA observing runs are expected to detect a subpopulation of eccentric signals, making it vital to develop accurate waveform models for eccentric orbits. Here, employing recent analytical results through the third post-Newtonian order, we develop seobnrv5ehm: a new time-domain, effective-one-body, multipolar waveform model for eccentric binary black holes with spins aligned (or antialigned) with the orbital angular momentum. Besides the dominant (2, 2) mode, the model includes the (2, 1), (3, 3), (3, 2), (4, 4), and (4, 3) modes. We validate the model’s accuracy by computing its unfaithfulness against 99 (28 public and 71 private) eccentric numerical-relativity (NR) simulations, produced by the Simulating eXtreme Spacetimes Collaboration. Importantly, for NR waveforms with initial GW eccentricities below 0.5, the maximum (2, 2)-mode unfaithfulness across the total mass range $20–200M_{\odot }$ is consistently below or close to 1%, with a median value of $\sim 0.02\%$, reflecting an accuracy improvement of approximately an order of magnitude compared to the previous-generation seobnrv4ehm and the state-of-the-art teobresums-dalí eccentric model. In the quasi-circular-orbit limit, seobnrv5ehm is in excellent agreement with the highly accurate seobnrv5hm model. The accuracy, robustness, and speed of seobnrv5ehm make it suitable for data analysis and astrophysical studies. We demonstrate this by performing a set of recovery studies of synthetic NR-signal injections, and parameter-estimation analyses of the events GW150914 and GW190521, which we find to have no eccentricity signatures.

Accurate waveform models for coalescing binaries on eccentric orbits are crucial for avoiding biases in the analysis of eccentric gravitational-wave signals. The effective-one-body (EOB) formalism combines various analytical approximation methods with information derived from numerical-relativity simulations, and it has proven reliable in modeling the inspiral-merger-ringdown waveform of binaries on generic orbits. In this work, we derive new analytical results within the EOB formalism, specifically addressing eccentric, aligned-spin binaries. For the first time, we obtain EOB results for eccentric orbits that are accurate up to the third post-Newtonian (PN) order for the complete far-zone energy and angular-momentum fluxes, the radiation-reaction (RR) force, and waveform modes (including memory contributions). We obtain these results by deriving transformations from the harmonic to EOB coordinates and from the quasi-Keplerian to the Keplerian parametrization, that properly account for the spin-supplementary condition, postadiabatic contributions, and the gauge freedom in the RR force. We employ these findings to build the inspiral part of the seobnrv5ehm waveform model, which includes the 3PN eccentricity contributions in the RR force and waveform modes using the Keplerian parametrization, and augments the EOB equations of motion with PN evolution equations for the Keplerian parameters. The new seobnr model achieves much better accuracy than its predecessor seobnrv4ehm and other eccentric models, even for eccentricities as high as $\lesssim 0.5$.

The conservation of the long wavelength fluctuations of the metric plays a vital role in cosmology as the link between quantum fluctuations during inflation and late time observations. This is a well-known property of the classical evolution equations, but demonstrating that it is robust to quantum correction involves a number of technical arguments. In this paper, we will use effective field theory (EFT) techniques to demonstrate the all orders conservation of the superhorizon scalar and tensor fluctuations of the metric during inflation. We show how to construct an EFT for these soft modes, in analogy with soft de Sitter effective theory. We pay particular attention to how the breaking of time diffeomorphisms by the inflationary background introduces new timescales that alter the structure of the EFT. In this description, the all orders conservation of the metric fluctuations is a direct consequence of symmetries and power counting that cannot be altered by loop corrections. We further show that this holds when the inflaton (or metric fluctuations) is coupled to additional heavy fields, as in quasi-single-field inflation. We match this behavior to several calculations in the ultraviolet (UV) theory and show how the Mellin representation enables a more transparent connection between the UV and the EFT descriptions.