We reexamine the mode structure of first-order relativistic hydrodynamics in flat spacetime with a global $U(1)$ symmetry from the perspective of low energy effective field theory. Using the Schwinger-Keldysh formalism, we show that boost invariance is realized nonlinearly and that the associated Nambu-Goldstone modes resolve the apparent instabilities encountered in conventional treatments. In a consistent derivative expansion, our formulation yields a frame invariant, gapless infrared spectrum of hydrodynamic modes that is stable if the enthalpy density is positive. The issue of well-posedness of partial differential equations is ultraviolet and must be kept distinct from the question of first order hydrodynamics as an effective theory. Our results indicate that, first order hydrodynamics has no internal inconsistency on its domain of applicability, and with an appropriate cutoff one can carry out analytic applications such as loop and fluctuation analyses without the frame dependence.

We demonstrate that the complete and nonredundant set of Landau singularities of Feynman integrals may be explicitly obtained from the Whitney stratification of a certain map. As a proof of concept, we leverage recent theoretical and algorithmic advances in their computation in order to determine this set for nontrivial examples of two-loop integrals. Interestingly, different strata of the Whitney stratification describe not only the singularities of a given integral, but also those of integrals obtained from kinematic limits, e.g., by setting some of its masses or momenta to zero.

We develop a QCD-assisted relaxation dynamic model for the critical mode of the critical end point (CEP) in the QCD phase diagram, which allows us to investigate the critical slowing-down effect quantitatively in the QCD phase diagram, especially in the proximity of the CEP, without any phenomenological parameters. The relaxation time from nonequilibrium to equilibrium in the QCD phase diagram is extracted from the Langevin simulations of the QCD-assisted relaxation dynamic model. It is found that in a narrow region along the phase boundary radiated from the CEP, the relaxation time is enhanced significantly. Outside this narrow region, the relaxation time drops drastically, which implies that the dynamic critical region is small in the QCD phase diagram. Within the present setup in this work, we further find that the relaxation time is not strongly enhanced along the considered chemical freeze-out curves, suggesting that the effects of critical slowing down may be limited there.

Exchange of two neutrinos (as well as other fermions) generates a long-range parity-violating potential of the form $\sim G^2/r^5$, with characteristic range $\hslash /(2m_{\nu }c)$. In atomic systems the corresponding matrix elements converge at distances $r<10/M_Z$, so that the interaction between electron and quarks effectively reduces to a contact term $\sim G^2{M}_Z^2{\delta }^3(\overrightarrow{r})\sim G\alpha {\delta }^3(\overrightarrow{r})$. This interaction produces a $-0.8\%$ correction to the effective weak charge of cesium, resolving the $2\sigma$ discrepancy between the Standard Model prediction and the measured Cs parity-violation amplitude. The corresponding value of the weak mixing angle is ${\sin }^2{\theta }_W=0.2375(19)$ at $q^2\approx 0$, in agreement with the Standard Model prediction ${\sin }^2{\theta }_W=0.23873$. The relative correction to the proton weak charge is about 3%. Using these results, we revisit the limits on an additional $Z^{\prime }$ boson and obtain a constraint on isospin-conserving oblique radiative corrections characterized by the Peskin–Takeuchi parameter $S=-0.32(53)$ at $q^2\approx 0$.

Recent measurements of charmed-baryon semileptonic decays signal large tensions between experiment and theory, including $SU(3{)}_F$ analyses and lattice-quantum chromodynamics simulations. Possible sources of the discrepancy include the experimental normalization mode ${\mathrm{\Xi }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$. Using lattice-quantum chromodynamics inputs in an $SU(3{)}_F$ analysis including first-order symmetry breaking, we predict $\mathcal{B}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^0{\ell }^{+}{\nu }_{\ell })/\mathcal{B}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Xi }}^0{\ell }^{+}{\nu }_{\ell })=(2.6\pm 0.3)\%$, and $\mathcal{B}({\mathrm{\Xi }}_c^{+}\to \mathrm{\Lambda }{\ell }^{+}{\nu }_{\ell })/\mathcal{B}({\mathrm{\Xi }}_c^{+}\to {\mathrm{\Xi }}^0{\ell }^{+}{\nu }_{\ell })=(1.1\pm 0.1)\%$, with ${\ell }^{+}=(e^{+},{\mu }^{+})$. These ratios provide normalization-independent tests and may help clarify the origin of the present tension.

Understanding the internal structure of the proton—including the distributions of quarks and gluons and their contributions to proton properties such as mass—remains a central challenge in quantum chromodynamics (QCD). While quark generalized parton distributions (GPDs) have been studied extensively, a consistent approach that simultaneously extracts quark parton distribution functions (PDFs), gravitational form factors (GFFs), and gluon GPDs from experimental constraints is still lacking. Moreover, the role of gluons in proton mass generation, particularly through the trace anomaly mechanism, requires deeper theoretical and phenomenological exploration. In this study, we begin by extracting quark GPDs in protons using a parametrization method based on the electromagnetic form factors provided by light-front holographic QCD (LFHQCD), from which we derive both quark PDFs and their GFFs. Our contribution lies in adopting a distinct functional form for $w(x,t)$ and extending this approach to model gluon GPDs. Our calculations show consistency with experimental data and lattice QCD results and successfully reproduce soft Pomeron behavior. Furthermore, we investigate near-threshold $J/\psi$ production using gauge/string duality to quantify the contribution of the trace anomaly to the proton mass. Our results indicate that the parametrization method provides a consistent framework for describing both quark and gluon structure, bridging GPDs, PDFs, and GFFs. The analysis of $J/\psi$ production confirms that the trace anomaly contributes significantly ($\sim 24\%$) to the proton mass, with the calculated cross-section dependence on momentum transfer $t$ in agreement with experimental observations. This work advances the understanding of proton structure by integrating quark and gluon degrees of freedom and elucidating the origin of proton mass within QCD.

We study various types of holographic solutions from five-dimensional $N=4$ gauged supergravity coupled to three vector multiplets with $SO(2)\times ISO(3)$ gauge group. This gauged supergravity can be obtained from the maximal gauged supergravity in seven dimensions on a Riemann surface. For a negatively curved Riemann surface $H^2$, the resulting five-dimensional gauged supergravity admits a supersymmetric $N=4$ ${\mathrm{AdS}}_5$ critical point. This ${\mathrm{AdS}}_5$ vacuum is dual to an $N=2$ superconformal field theory (SCFT) arising from M5-branes wrapped on $H^2$. We study holographic RG flows between this SCFT and $N=2$ nonconformal phases by deformations involving relevant, marginal and irrelevant operators. Solutions describing conformal interfaces between these nonconformal phases and singular boundaries are also given. We finally study a number of supersymmetric ${\mathrm{AdS}}_5$ black string and black hole solutions holographically dual to RG flows across dimensions from the $N=2$ SCFT to two-dimensional SCFTs and superconformal quantum mechanics in the IR. A number of solutions describing black strings and black holes in asymptotically domain wall space-time are also found. All of the solutions can be uplifted to M-theory by a consistent truncation on $H^2\times S^4$.

This work deepens the study of integrable asymptotic symmetries for ${\mathrm{AdS}}_3$. They are given by an infinite set of integrable nonlinear equations known as the Ablowitz-Kaup-Newell-Segur (AKNS) hierarchy, characterized by an also infinite set of Abelian conserved charges. We present their field-dependent Killing vectors and the computation of the canonical charges associated to the asymptotic metric, together with their corresponding charge algebra. We study black hole thermodynamics and show that the temperature for stationary black holes falling in the AKNS asymptotics is always constant, even in the case where the solutions are not axisymmetric. The temperature is directly encoded in the spectral polynomial of the corresponding stationary Schrödinger problem, highlighting a precise connection between thermodynamic quantities and the spectral data of quantum integrable systems. This is related to the existence of a hyperelliptic curve, which appears as a fundamental object in many integrable systems. We also present a special solution associated with the Korteweg-de Vries (KdV) equation, that is a particular case of the AKNS integrable hierarchy. It is presented in the form of a periodic soliton leading to a cnoidal KdV black hole, whose temperature is characterized by two copies of hyperelliptic curves.

In this paper we construct solutions with AdS/dS asymptotics for $D=3$ truncated gauged supergravity with a periodic scalar potential. In a holographic perspective, assuming Dirichlet boundary conditions, the solutions can be interpreted as deformations of two-dimensional dual conformal field theories triggered by nonzero vacuum expectation values (VEVs) of irrelevant operators. In addition to the domain-wall-type solutions, we incorporated in the analysis a black string solution, which can also be interpreted as a deformation by VEV of an irrelevant operator. Generalizing the flows to finite temperature, we find that the corresponding geometries are singular but have horizons. For certain flows, we provide an analytical description near the horizon region. For an exact renormalization group (RG) flow solution, we explicitly compute the Brown-York stress-energy tensor on a cutoff surface and show that the $T\overline{T}$ operator factorizes along the holographic RG flow. We also define an effective, scale-dependent deformation parameter $\mu (\varphi )$, whose running is governed by the scalar field at the cutoff.

We study the quantum dynamics of the Schwarzschild interior in the Ashtekar-Barbero formulation, focusing on the fate of the classical singularity and the annihilation-to-nothing scenario. Using minisuperspace Wheeler-DeWitt quantization, we first analyze the standard Schrödinger representation and show that the annihilation-to-nothing behavior appears only for a specific choice of factor ordering and is not generic. We then introduce a generalized uncertainty principle (GUP), which induces minimal length effects through a deformation of the canonical algebra. Solving the modified Wheeler-DeWitt equation and constructing Gaussian wave packets localized at the horizon, we find that the annihilation-to-nothing behavior is suppressed once the GUP corrections are included. Our results indicate that minimal length effects qualitatively alter the quantum interior dynamics and challenge the robustness of this scenario as a mechanism for singularity resolution.

Black hole islands are usually diagnosed through the von Neumann entropy, but the full replica saddle contains more information than survives in the limit $n\to 1$. In this paper we show that the capacity of entanglement can detect that extra structure already within the controlled factorized island branch of Jackiw-Teitelboim gravity coupled to a large-$c$ bath. In the late-time high-temperature regime, the entropy plateau remains unchanged at the first nontrivial order, while the capacity acquires a definite correction. This provides a sharp semiclassical example in which nearby replica data are physically meaningful even when the entropy itself appears rigid. Our result shows that the factorized island saddle already carries finite-$n$ information beyond the entropy, and that the capacity is a natural observable for exposing it. More broadly, it highlights that the physics of island saddles is not exhausted by the $n=1$ limit: the surrounding replica geometry can contain additional, and observable, information about how the semiclassical saddle is assembled.

The prospect of detecting gravitationally induced entanglement (GIE) in a laboratory setting within the coming decades has prompted considerable debate about what such a finding would imply for our understanding of the quantum nature of gravity. As a step toward grounding this debate in our most fundamental description of matter, we develop a quantum field-theoretic model of GIE between two massive objects in spatial superposition. The masses are described as excitations of a scalar field in an external harmonic potential, allowing for a well-defined notion of relativistic coherent states. Using linearized quantum gravity in the static limit, we derive an effective Hamiltonian that induces entanglement between the field modes occupied by the masses. To probe this entanglement, we construct an observable from field operators that corresponds to the probability density of detecting the center of mass of one of these massive objects. Using this observable, we compute the fringe visibility in the overlap region and find that gravitationally induced entanglement leads to a decrease in visibility, consistent with previous nonrelativistic results. Additionally, we identify relativistic corrections that accelerate the decay of fringe visibility. These results provide a framework for studying weakly relativistic quantum field systems and their gravitational interactions in tabletop experiments.

We propose a nonperturbative completion of two-point correlators in $T\overline{T}$-deformed conformal field theories (CFTs) and analyze their behavior at distance scales shorter than the fundamental length scale set by the $T\overline{T}$ deformation. Building on the interpretation of the $T\overline{T}$ deformation as a coupling to two-dimensional quantum gravity with a unique built-in length scale, we advance the study of $T\overline{T}$-deformed CFTs as a toy model for Planckian physics. As we probe shorter distances, trans-Planckian oscillations are followed by a super-Planckian regime in which correlations are typically suppressed by geometric randomness, in contrast to the power-law growth characteristic of CFTs. Moreover, their dependence on distance becomes exponentially weaker, suggesting that the underlying geometric structure has been largely erased—a behavior broadly consistent with expectations for quantum spacetime in this regime.

We consider hairy, magnetic black brane solutions to Einstein-Maxwell-Chern-Simons-Dilaton theory with full backreaction of the scalar and gauge fields and compute the time evolution with time dependent sources. The dual field theory’s ’t Hooft anomaly leads to long-lived current oscillations in the low temperature limit long after the electric pulse which created these modes has been switched off. We find that, generally, nonlinear effects increase the decay rates of long-lived modes by a temperature dependent amount. Nonetheless, our results suggest that the lifetime of time-translation symmetry breaking states can be made arbitrarily large if the temperature after the quench is sufficiently small. Experimentally this might be realizable in Weyl semimetals.

We consider two-point functions of light fields at finite temperature and large real frequencies in holographic theories. The thermal system is dual to a single-sided anti–de Sitter black hole. We show that the high-frequency expansion obtained from the operator product expansion receives exponentially small nonperturbative corrections, which are controlled by null geodesics bouncing off the black hole singularity in the two-sided eternal black hole geometry. We develop a bulk WKB description of these bouncing geodesics and explain how to calculate reflection coefficients at the singularity.

We derive the Lehmann-Symanzik-Zimmermann reduction formalism for a massive spin-2 particle on Minkowski spacetime and extend the formalism to cosmological spacetimes. The reduction formalism allows for a versatile proof that the Goldstone boson equivalence theorem holds in Friedmann-Lemaître-Robertson-Walker spacetimes. For the de Sitter and the radiation-filled universe, we investigate the Goldstone dynamics and perform an analysis of the range of validity provided by the effective kinetic operator.

We present the first computation of the gauge-invariant, long-wavelength scattering amplitude for the graviton photoproduction by a Kerr-Newman black hole through $\mathcal{O}((\omega m{)}^2)$, or correspondingly $\mathcal{O}(S^2)$, and to linear order in $G$, using the worldline effective field theory. We show that electromagnetic interactions can be introduced consistently into the spinning worldline theory while preserving spin gauge invariance. We also derive the full angular dependence of the conversion cross section through $\mathcal{O}(S^2)$, and demonstrate that the relevant Wilson coefficients at this order are fixed entirely by matching the electromagnetic and gravitational multipole moments to the Kerr-Newman solution. This result provides a benchmark for future analyses of coupled gravitoelectromagnetic scattering in spinning, charged compact-object backgrounds.

Periodic structures are ubiquitous in quantum many-body systems and quantum field theories, ranging from lattice models, to compact spaces, to topological phenomena. However, previous bootstrap studies encountered technical challenges even for one-body periodic problems, such as a failure in determining the accurate dispersion relations for Bloch bands. In this work, we develop a new bootstrap procedure to resolve these issues, which does not make use of positivity constraints. We mainly consider a quantum particle in a periodic cosine potential. The same procedure also applies to a particle on a circle, where the role of the Bloch momentum $k$ is played by the boundary condition or the $\theta$ angle. We unify the natural set of operators and the translation operator by a new set of operators $\{e^{inx}{e}^{iap}{p}^s\}$. To extract the Bloch momentum $k$, we further introduce a set of differential equations for $⟨e^{inx}{e}^{iap}{p}^s⟩$ in the translation parameter $a$. At some fixed $a$, the boundary conditions can be determined accurately by analytic bootstrap techniques and matching conditions. After solving the differential equations, we impose certain reality conditions to determine the accurate dispersion relations, as well as the $k$ dependence of other physical quantities. We also investigate the case of noninteger $s$ using the Weyl integral in fractional calculus.

To create a static traversable wormhole, exotic matter that meets the Morris-Thorne conditions is required. It is well known that the expectation value of the vacuum stress-energy tensor can violate the null energy condition and thus has long been considered the best candidate for exotic matter. In this paper, we investigate whether the renormalized stress-energy tensor of a nonminimally coupled massive scalar field in a zero-tidal wormhole can satisfy the Morris-Thorne conditions. Within the Hadamard renormalization framework, we calculate the renormalized stress-energy tensor using the pragmatic mode-sum regularization method recently established by Levi and Ori. By varying the dimensionless scalar field mass and coupling constant, we find that there are three disconnected regions in this two-dimensional parameter space that satisfy the Morris-Thorne conditions. We identify two intervals in the dimensionless scalar field mass, within which the Morris-Thorne conditions cannot be satisfied irrespective of the value of the coupling constant. This establishes two mass exclusion regions that constitute a no-go regime for the construction of traversable wormholes.

The horizon multipole moments of a Kerr black hole are computed from two distinct definitions that have been proposed in the literature. The first one [Ashtekar et al., Classical Quantum Gravity 21, 2549 (2004)] regards axisymmetric isolated horizons, while the second one [Ashtekar et al., J. High Energy Phys. 01 (2022) 028] applies to generic (i.e., not necessarily axisymmetric) nonexpanding horizons. We review these definitions in a common frame and perform a detailed study of the resulting multipole moments for the Kerr event horizon. The horizon multipoles are found to share several properties with the (Hansen) field multipoles, including parity constraints and the leading scaling behavior with respect to the Kerr spin parameter $a$ in the regime of small $a$. For the axisymmetry-based definition, we have obtained a closed-form expression of the multipole moments in terms of $a$ and the spherical harmonic degree $\ell$. For the generic definition, we have established closed-form expressions for the conformal unit round metric, the “electric” and “magnetic” potentials related to the multipoles, and the values of the multipoles in the small $a$ limit. We show that the two definitions lead to different values of the Kerr horizon multipoles as soon as $\ell ⩾1$ (generic nonzero value of $a$) or $\ell ⩾2$ (small $a$ limit).