Nuclear Theory·nucl-th

Wednesday·May 6, 2026

10 papers—3 primary·7 cross-listed

01
Chiral symmetry breaking and inhomogeneous phases in thermal anti-de Sitter spacetime
Sergio Morales-Tejera🇷🇴
We study the spontaneous breaking of chiral symmetry in an AdS spacetime at finite temperature using the quark-meson model. The condensate $σ$ is typically inhomogeneous in AdS and is determined from the differential gap equation. We demonstrate that there are no free integration constants in the regular solutions to the differential equation and find that the solution to the boundary value problem is unique. We find that chiral symmetry is always broken close to the AdS boundary. We construct the phase diagram of the system as a function of the AdS curvature and temperature. These two parameters have opposing effects: temperature tends to restore chiral symmetry, whereas negative curvature favors its spontaneous breaking. We also consider how the phase diagram is modified when the Hawking-Page phase transition is taken into account.
nucl-thhep-th0 citations
02
Inclusive breakup of three-body projectiles: A unified four-body framework for pair-detected and single-particle observables
Jin Lei
Inclusive breakup of three-body projectiles $a = i + j + k$ on a target $A$ admits two distinct inclusive observables: detection of a correlated pair $b = (ij)$ with $k + A$ unresolved, and detection of a single particle $i$ with $j k + A$ unresolved. A four-body DWBA sum-rule framework is derived for both channels from a common Hamiltonian. For the pair-detected channel, the unresolved propagator remains the two-body $k + A$ Green function and all three-body projectile effects enter through a pair-projected source built from $Φ_{a}$ ; a reference pair-target optical interaction splits this source into a target-elastic reference part and an explicit pair-target coupling part, yielding a state-resolved semi-inclusive coincidence observable and an amplitude-level diagnostic of the two-body cluster approximation. For the single-particle channel, the unresolved propagator is the three-body $j k + A$ resolvent, whose reference-channel Feshbach reduction reproduces the Carlson-Frederico-Hussein (CFH) absorptive kernel $W_{j} + W_{k} + W_{3 B}$ ; the additional source $V_{i A} - U_{i A}$ drives target excitations, with its direct $g_{Q}$ component yielding target-excited CFH-like kernels under a diagonal-intermediate-states approximation. Prior forms are derived for both partitions, with reduced post-prior identities at the single-channel level (pair-detected) and at the CFH-optical level (single-particle). For $^{6}$ Li $= α + n + p$ , the explicit deuteron-target coupling has an E1/E2/monopole tidal structure evaluated on the full three-body wave function. The framework is validated by recovery of the two-body IAV, CFH, and detected-cluster limits, and separates exact DWBA identities from later optical and diagonal-target approximations.
nucl-th0 citations
03
What is a resonance? And why does it matter?
Sebastian König🇺🇸 · Kévin Fossez🇺🇸 · Rimantas Lazauskas🇫🇷
The resonance phenomenon is of central importance in many areas of physics, with particular significance in the study of nuclear structure and reactions. Starting from the classical framework of damped driven oscillations, this text introduces and analyzes quantum-mechanical resonances in a pedagogical and systematic fashion, with emphasis on applications in nuclear physics. Building on the formal theory of resonances, the text elucidates the relationship between experimental observations, phenomenological insights, and computational methods used to characterize and describe resonant states. The discussion encompasses the diverse manifestations of nuclear resonances, ranging from few- to many-body systems, all the way to collective phenomena and to exotic systems that appear near the limits of nuclear stability. References to the relevant literature are provided to assist readers who wish to explore specific topics in more depth.
nucl-th1 citation
04
Soft mode dynamics associated with QCD critical point and color superconductivity -- pseudogap, anomalous dilepton production and electric conductivity
Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵
We give a systematic account of the soft mode dynamics of QCD critical point and the two-flavor color-superconductivity based on the 2-flavor Nambu--Jona-Lasinio model, and investigate their effects on electromagnetic observables in relativistic heavy-ion collisions (HIC). We first demonstrate that the collective excitations coupled to the fluctuations of the respective order parameters are the soft modes associated with the phase transitions, in the sense that they acquire a prominent spectral strength in the low-energy and low-momentum region near the phase transitions, and the peak energy goes down, i.e., gets softened, and eventually vanishes at the critical point. It is shown that the diquark soft mode of the 2SC gives rise to the pseudogap, i.e., a depression in the density of states of the quark spectra around the Fermi surface above but in the vicinity of the critical temperature. Then, exploiting the ideas that were developed in condensed matter physics for describing the `para-conductivity' in the normal phase of metal superconductors, we show that the soft modes cause an anomalous enhancement of electric conductivity and the dilepton production rate, and discuss their relevance to HIC.
↳ hep-phnucl-thSymmetry(2026)·0 citations
05
Calculating extremely high energy bremsstrahlung in matter
Peter Arnold🇺🇸 · Joshua Bautista🇺🇸 · Omar Elgedawy🇨🇳 · Shahin Iqbal🇵🇰
Ultra-relativistic electrons initiate electromagnetic showers in ordinary matter that evolve through bremsstrahlung and pair production. At very high energy, the quantum mechanical duration of bremsstrahlung becomes longer than the mean free time to elastically scatter from the medium, leading to a significant suppression known at the Landau-Pomeranchuk-Migdal (LPM) effect. For some ranges of bremsstrahlung photon and initial electron energies $(k_{γ}, E)$ , the duration becomes so long that it will also overlap with subsequent pair production by the bremsstrahlung photon, disrupting LPM suppression and drastically changing LPM predictions. We have previously calculated this change for extremely high energies ( $k_{γ} ≫ 2$ TeV or more, depending on the medium), for which the electron mass and medium-induced photon mass could be ignored. In this paper, we extend that analysis to lower (but still ultra-relativistic) energy by accounting for those masses, leading to a rich map of behavior in different regions of $(k_{γ}, E)$ .
↳ hep-phnucl-th0 citations
06
Squeezed-state radiation in shockwave scattering: QCD-Gravity double copy
Anna M. Staśto🇺🇸 · Himanshu Raj🇺🇸 · Raju Venugopalan🇺🇸
Gluon and graviton radiation in strong field shockwave scattering are described by effective Lipatov vertices, with the graviton Lipatov vertex proportional to the bilinear of its QCD counterpart. We show here that the n-particle gluon radiation spectrum can be described as a generalized Susskind-Glogower (gSG) squeezed coherent state and discuss the properties of such squeezed states. The double copy structure of the radiative frameworks suggests that multi-graviton radiation can be similarly described as a gSG state. We examine the physical parameter space and show that very large squeezing parameters $\sim ln (n ˉ)$ (where $n ˉ$ is the mean graviton occupancy) are feasible for nearly minimal uncertainty configurations of the gSG state. Quantum noise in the corresponding gravitational wave spectrum is enhanced above the sensitivity of current and future gravitational wave detectors. Our results point to the importance of a comprehensive study of the strong field Lipatov regime of gravitational radiation.
↳ hep-thgr-qchep-phnucl-thActa Phys.Polon.B(2026)·0 citations
07
Parton Distribution Functions from Large Momentum Expansion of Current-Current Correlators
Jialu Zhang🇨🇳 · Xiangdong Ji🇺🇸 · Andreas Schäfer🇨🇳 · Rui Zhang🇺🇸 · Christian Zimmermann🇺🇸
The universality of the large momentum expansion allows computing parton distribution functions (PDFs) starting from any Euclidean correlator with appropriate large momentum Fourier Components. Here we consider current-current correlators which have been used in short-distance expansion to obtain moments of PDFs. The advantage of such correlators is that they have simple renormalization properties and do not have linear power divergences as in quasi-PDF. However, in lattice calculations, four-point functions are needed. Here we present an expansion formula with current-current correlators up to the next-to-leading order, and preliminary numerical calculations with four-point functions.
↳ hep-phhep-latnucl-th2 citations
08
Non-radial pulsations of gravitationally coupled two-fluid neutron stars in general relativity
Ankit Kumar · Daniel A. Caballero · Hajime Sotani · Nicolás Yunes
Non-radial oscillations of neutron stars provide a powerful probe of stellar structure and relativistic gravity, but a fully general relativistic treatment for gravitationally coupled two-fluid stars with independently conserved currents has so far been lacking. In this work, we develop a fully relativistic framework for polar perturbations of gravitationally coupled two-fluid neutron stars, assuming that the two fluids interact only through the common spacetime and are not coupled by entrainment or direct microphysical interactions. We derive the coupled linear perturbation equations governing the metric and both fluid components, and complete the formulation by establishing the regularity, surface, and exterior matching conditions required for a well-posed oscillation eigenvalue problem. We then implement the resulting system numerically and compute representative polar mode spectra for gravitationally coupled two-fluid stellar models. This implementation provides a practical way to address mode identification in gravitationally coupled two-fluid stars, allowing the fundamental ( $f$ ) and pressure ( $p$ ) mode branches of the spectrum to be classified according to their dominant inner- or outer-fluid character through the associated eigenfunctions and their node structure. The formalism developed here provides a foundation for extending relativistic asteroseismology to multi-fluid compact stars and for exploring their potential gravitational-wave signatures in a fully general relativistic setting.
↳ gr-qcastro-ph.HEhep-thnucl-thPRD(2026)·4 citations
09
Exclusive photoproduction of a di-meson pair with large invariant mass
Saad Nabeebaccus🇫🇷 · David Perez🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
The exclusive photoproduction of a pair of light mesons is studied within the framework of collinear factorisation. The amplitude factorises into a process-dependent perturbatively calculable hard part, a generalised parton distribution (GPD) and two distribution amplitudes (DAs). We focus on the production of any combination of $ρ$ and $π$ mesons (of any charge and polarisation) that do not involve neutral $C = +$ exchanges with the nucleon. This gives a total of 26 distinct channels, which are sensitive to quark GPDs only. We calculate the amplitude for this family of di-meson processes at leading order in the strong coupling constant $α_{s}$ and at leading twist, in a fully-automated way. Depending on the choice of mesons in the final state, some of these processes are sensitive to chiral-odd (helicity-flip) GPDs. Particular attention is given to the treatment of poles in the 3-dimensional convolution integral of the momentum fractions connecting the hard part with the different non-perturbative components. These poles are regularised by the usual Feynman $i ϵ$ factors, but lead to numerical instabilities if not dealt with properly. We also discuss in detail the construction of the phase space. Importantly, we propose a resolution for the inconsistency of the kinematics of the hard part of the process, where hadron masses and other soft scales are neglected, with the rest of the process. As a proof of concept, we explicitly evaluate the cross section, for a subset of processes whose amplitudes have been constructed, at energies typical of the CLAS12 experiment at JLab. Our results indicate that exclusive di-meson photoproduction processes have very good statistics, which can be a factor of up to a hundred more than the exclusive photon-meson photoproduction process. Therefore, the family of processes that we study here represents a great opportunity for GPD extraction.
↳ hep-phhep-exnucl-exnucl-th0 citations
10
Late-Time Relaxation from Landau Singularities
Dong-Lin Wang🇨🇳 · Shi Pu🇨🇳
Nonlinear hydrodynamic interactions can change the relaxation of fluctuations from exponential to power-law decay at late times. Schwinger-Keldysh effective field theory provides a standard framework for describing such fluctuation effects, where the nonlinear late-time behavior is encoded in loop corrections. Extracting this behavior requires identifying the singularities of loop integrals, whose structure becomes increasingly intricate beyond simple models. We apply Landau singularity analysis to two-point functions in effective field theories and determine the singularities induced by nonlinear interactions without performing the loop integrations explicitly. From these frequency-space singularities, we extract nonlinear relaxation modes that control the late-time behavior. When gapless modes are present, these modes produce power-law decay at late times. Our results give a systematic singularity-based description of nonlinear late-time relaxation in a broad class of macroscopic effective theories.
↳ hep-thcond-mat.stat-mechhep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE