To access information on the internal structure of the nucleon, data from a variety of scattering experiments can be analyzed in regimes where the information factorizes from an otherwise known scattering amplitude. A recent development, promising new insight, is the study of exclusive reactions in the backward kinematical region, where the information can be encoded in transition distribution amplitudes. We model the photon-to-nucleon transition distribution amplitudes, entering the factorized description of backward timelike Compton scattering, using techniques of light-front dynamics to integrate information from a quark model for the photon and the nucleon. We include the results of numerical predictions that could inform further experiments at Jefferson Lab and the future Electron-Ion Collider.

Critical phenomena emerging from the critical end point of a first-order transition are ubiquitous in nature. Here we bring the concept of a supercritical crossover, the Widom line, initially developed in the context of fluids, into the interacting matter described by quantum chromodynamics (QCD). We show that the existence of the putative critical end point between hadron gas and quark-gluon plasma in the temperature versus chemical potential of the QCD phase diagram implies the existence of a Widom line emerging from it in the supercritical region. We survey the thermodynamic anomalies already identified in simplified theoretical models of QCD exhibiting a critical end point, to show that they can be interpreted in terms of a Widom line. Then we suggest possible directions where the Widom line concept could provide new light on the QCD phase diagram.

Recently, the propagation of information through quantum many-body systems, developed to study quantum chaos, have found many applications from black holes to disordered spin systems. Among other quantitative tools, Krylov complexity has been explored as a diagnostic tool for information scrambling in quantum many-body systems. We introduce a universal limit to the growth of the Krylov complexity in dissipative open quantum systems by utilizing the uncertainty relation for non-Hermitian operators. We also present the analytical results of Krylov complexity for characteristic behavior of Lanczos coefficients in dissipative systems. The validity of these results is demonstrated by explicit study of transverse-field Ising model under dissipative effects.

We present the first non-BPS (Bogomol’nyi-Prasad-Sommerfield) exact solution of an asymptotically flat, stationary spherical black hole having domain of outer communication with nontrivial topology in five-dimensional minimal supergravity. It describes a charged rotating black hole capped by a disk-shaped bubble. The existence of the “capped black hole” shows the nonuniqueness of spherical black holes.

Stationary, asymptotically flat, black hole solutions of the vacuum field equations of general relativity belong to the Kerr family. But how does one approach this state, dynamically? Linearized fluctuations decay at late times, at fixed spatial position, as a Price power law for generic initial conditions. However, little attention was paid to forced and nonlinear spacetimes, where matter and nonlinearities play a role. We uncover a new, source-driven tail governing waves generated by pointlike matter and nonlinearities, which can dominate over Price’s decay.

The causal-stable Müller-Israel-Stewart (MIS) theory is known to have a finite number of out-of-equilibrium derivative-order corrections but requires treating the viscosity tensor as a separate degree of freedom with its own equations of motion, apart from the fundamental fluid degrees of freedom like velocity and temperature. In this work, I will show that it is possible to rewrite the MIS theory only in terms of velocity and temperature, but the resultant constitutive relation for dissipation must include all orders of gradient corrections. In this work, I will argue that an all-order resummation of gradient contributions is equivalent to introducing new “nonfluid” degrees of freedom in the MIS theory. It will also be shown, using the relativistic quantum causality condition, that any finitely truncated order of derivative correction, however high it is, leads to a theory that is acausal, unless the corrections are infinitely summed up to all orders.

We demonstrate that the dip observed near the total energy of 3872 MeV in the recent cross section data from the BESIII Collaboration for $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}$ admits a natural explanation as a coupled-channel effect: it is a consequence of unitarity and a strong $S$-wave $D{\overline{D}}^{*}$ attraction that generates the state $X(3872)$. We anticipate the appearance of a similar dip in the $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}{\pi }^0$ final state near the $D^{*}{\overline{D}}^{*}$ threshold driven by the same general mechanism, then to be interpreted as a signature of the predicted spin-2 partner of the $X(3872)$.

In ABJM theory, enriched RG flows between circular $1/6$ BPS bosonic and $1/2$ BPS fermionic Wilson loops have been introduced in L. Castiglioni et al. [L. Castiglioni, S. Penati, M. Tenser, and D. Trancanelli, Interpolating Wilson loops and enriched RG flows, J. High Energy Phys. 08 (2023) 106.]. These flows are triggered by deformations corresponding to parametric $1/6$ BPS fermionic loops. In this paper, we revisit the study of these operators, but instead of circular contours, we consider an interpolating cusped line and a latitude and study their RG flow in perturbation theory. This allows for the definition of a bremsstrahlung function away from fixed points. We generalize to this case the known cusp/latitude correspondence that relates the bremsstrahlung function to a latitude Wilson loop. We find that away from the conformal fixed points the ordinary identity is broken by the conformal anomaly in a controlled way. From a defect perspective, the breaking of the correspondence can be traced back to the appearance of an anomalous dimension for fermionic operators localized on the defect. As a by-product, we provide a brand new result for the two-loop cusp anomalous dimension of the $1/6$ BPS fermionic and the $1/6$ BPS bosonic Wilson lines.

We study radiation from charged particles in circular motion around a Schwarzschild black hole immersed in an asymptotically uniform magnetic field. In curved space, the radiation reaction force is described by the DeWitt-Brehme equation, which includes a complicated, nonlocal tail term. We show that, contrary to some claims in the literature, this term cannot, in general, be neglected. We account for self-force effects directly by calculating the electromagnetic energy flux at infinity and on the horizon. The radiative field is obtained using black hole perturbation theory. We solve the relevant equations analytically, in the low-frequency and slow-motion approximation, as well as numerically in the general case. Our results show that great care must be taken when neglecting the tail term, which is often fundamental to capture the dynamics of the particle: in fact, it only seems to be negligible when the magnetic force greatly dominates the gravitational force, so that the motion is well described by the Abraham–Lorentz–Dirac equation. We also report a curious “horizon dominance effect” that occurs for a radiating particle in a circular orbit around a black hole (emitting either scalar, electromagnetic or gravitational waves): for fixed orbital radius, the fraction of energy that is absorbed by the black hole can be made arbitrarily large by decreasing the particle velocity.

Utilizing the recently established connection between Palatini-like gravity and linear generalized uncertainty principle (GUP) models, we have formulated an approach that facilitates the examination of Bose gases. Our primary focus is on the ideal Bose-Einstein condensate and liquid helium, chosen as illustrative examples to underscore the feasibility of tabletop experiments in assessing gravity models. The noninteracting Bose-Einstein condensate imposes constraints on linear GUP and Palatini $f(R)$ gravity (Eddington-inspired Born-Infeld gravity) within the ranges of $-{10}^{12}\lesssim \sigma \lesssim 3\times {10}^{24}\mathrm{s}/\mathrm{kg}\mathrm{m}$ and $-{10}^{-1}\lesssim \overline{\beta }\lesssim {10}^{11}{\mathrm{m}}^2$ ($-4\times {10}^{-1}\lesssim \epsilon \lesssim 4\times {10}^{11}{\mathrm{m}}^2$), respectively. In contrast, the properties of liquid helium suggest more realistic bounds, specifically $-{10}^{23}\lesssim \sigma \lesssim {10}^{23}\mathrm{s}/\mathrm{kg}\mathrm{m}$ and $-{10}^9\lesssim \overline{\beta }\lesssim {10}^9{\mathrm{m}}^2$. Additionally, we argue that the newly developed method employing Earth seismic waves provides improved constraints for quantum and modified gravity by approximately one order of magnitude.

Gravitational wave signals from core-collapse supernovae are one of the important observables for extracting the information of dense matter. To extract the properties of protoneutron stars produced via core-collapse supernovae by asteroseismology, we perform a linear perturbation analysis using data obtained from two-dimensional numerical simulations. We employ 12 and 20 solar-mass progenitors and compare two different treatments of gravity. One is a general relativistic one with a conformal flatness condition and the other is an effective gravitational potential mimicking the Tolman-Oppenheimer-Volkoff solution. We discuss how the frequencies of the protoneutron star oscillations corresponding to the gravitational wave signals in the simulations depend on the protoneutron star properties. In our models, we find that the gravitational wave frequencies of the protoneutron stars determined with the Cowling approximation can be expressed to very good approximation as a function of the protoneutron star average density almost independently of the progenitor mass, treatment of gravity in the simulations, and the interpolations in the simulations. On the other hand, if one considers the gravitational wave frequencies as a function of the surface gravity of protoneutron stars, such a relation appears sensitive to the treatment of gravity and other numerical details in the simulations. Thus, the average density of protoneutron stars seems more suitable for universally expressing the supernova gravitational wave frequencies, instead of the surface gravity.

We find a complete set of four-point vertices in the constructive Standard Model (CSM). This set is smaller than in Feynman diagrams as the CSM does not need or allow any additional four-point vertices (or “contact” terms) beyond what is present in Feynman diagrams and, furthermore, it does not need or allow a four-point vertex for $Z,Z,\overline{W},W$, $W,W,\overline{W},\overline{W}$, $\gamma ,Z,W,\overline{W}$ or $\gamma ,\gamma ,W,\overline{W}$, in addition to the already known absence of the four-gluon vertex. We show that with this set of four-point vertices, perturbative unitarity is satisfied in the CSM. Additionally, we show that many constructive diagrams are not Feynman diagrams rewritten in spinor form. In fact, we show that there is a significant rearrangement of contributions from the diagrams in constructive calculations relative to Feynman diagrams for some processes. In addition to the already known or expected rearrangement in diagrams involving external photons, we also find that diagrams involving four-vector bosons are also significantly different from their Feynman counterparts.

We present a method that maximizes the experimental sensitivity to new physics contributions in $B^{\pm }\to {\pi }^{\pm }{\mu }^{+}{\mu }^{-}$ decays. This method relies on performing an unbinned maximum likelihood fit to both the measured dimuon $q^2$ distribution of $B^{\pm }\to {\pi }^{\pm }{\mu }^{+}{\mu }^{-}$ decays, and theory calculations at spacelike $q^2$, where QCD predictions are most reliable. Using known properties of the decay amplitude we employ a dispersion relation to describe the nonlocal hadronic contributions across spacelike and timelike $q^2$ regions. The fit stability and the sensitivity to new physics couplings and new sources of $CP$-violation are studied for current and future data-taking scenarios, with the LHCb experiment as an example. The proposed method offers a precise and reliable way to search for new physics in these decays.

We calculate the form factors for the baryon number violation processes of a heavy-flavor baryon decaying into a pseudoscalar meson and a lepton. In the framework of the Standard Model effective field theory, the leptoquark operators at the bottom quark scale, whose matrix elements define the form factors, are derived by integrating out the high energy physics. Under the quantum chromodynamics (QCD) factorization approach, the form factors of the baryon number violation processes at leading power can be factorized into the convolution of the long-distance hadron wave functions as well as the short-distance hard and jet functions representing the hard scale and hard-collinear scale effects, separately. Based on measurements of the baryon number violation processes by LHCb, we further impose constraints on the new physics constants of leptoquark operators.

Low-energy Compton scattering is an important background for sub-GeV dark matter direct-detection and other experiments. Current Compton scattering calculations typically rely on assumptions that are not valid in the low-energy region of interest, beneath $\sim 50\mathrm{eV}$. Here we relate the low-energy Compton scattering differential cross section to the dielectric response of the material. Our new approach can be used for a wide range of materials and includes all-electron, band-structure, and collective effects, which can be particularly relevant at low energies. We demonstrate the strength of our approach in several solid-state systems, in particular, Si, Ge, GaAs, and SiC, which are relevant for current and proposed experiments searching for dark matter, neutrinos, and millicharged particles.

The quantum fluctuations of fields can exhibit subtle correlations in space and time. As the interval between a pair of measurements varies, the correlation function can change sign, signaling a shift between correlation and anticorrelation. A numerical simulation of the fluctuations requires a knowledge of both the probability distribution and the correlation function. Although there are widely used methods to generate a sequence of random numbers which obey a given probability distribution, the imposition of a given correlation function can be more difficult. Here we propose a simple method in which the outcome of a given measurement determines a shift in the peak of the probability distribution, to be used for the next measurement. We illustrate this method for three examples of quantum field correlation functions, and show that the resulting simulated function agrees well with the original, analytically derived function. We then discuss the application of this method to numerical studies of the effects of correlations on the random walks of test particles coupled to the fluctuating field.