Nuclear Theory·nucl-th

Tuesday·October 31, 2023

26 papers—12 primary·14 cross-listed

13
[Submitted on 18 Oct 2023] (cross-list from cond-mat.stat-mech)
Translation-invariant relativistic Langevin equation derived from first principles
Filippo Emanuele Zadra🇮🇹 · Aleksandr Petrosyan🇬🇧 · Alessio Zaccone🇮🇹
The relativistic Langevin equation poses a number of technical and conceptual problems related to its derivation and underlying physical assumptions. Recently, a method has been proposed in [A. Petrosyan and A. Zaccone, J. Phys. A: Math. Theor. 55 015001 (2022)] to derive the relativistic Langevin equation from a first-principles particle-bath Lagrangian. As a result of the particle-bath coupling, a new ``restoring force'' term appeared, which breaks translation symmetry. Here we revisit this problem aiming at deriving a fully translation-invariant relativistic Langevin equation. We successfully do this by adopting the renormalization potential protocol originally suggested by Caldeira and Leggett. The relativistic renormalization potential is derived here and shown to reduce to Caldeira and Leggett's form in the non-relativistic limit. The introduction of this renormalization potential successfully removes the restoring force and a fully translation-invariant relativistic Langevin equation is derived for the first time. The physically necessary character of the renormalization potential is discussed in analogy with non-relativistic systems, where it emerges due to the renormalization of the tagged particle dynamics due to its interaction with the bath oscillators (a phenomenon akin to level-repulsion or avoided-crossing in condensed matter). We discuss the properties that the corresponding non-Markovian friction kernel has to satisfy, with implications ranging from transport models of the quark-gluon plasma, to relativistic viscous hydrodynamic simulations, and to electrons in graphene.
Subjects:
Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2310.18327 [pdf]
PRD(2023)·4 citations
14
[Submitted on 27 Oct 2023] (cross-list from hep-ph)
QCD equation of state and thermodynamic observables from computationally minimal Dyson-Schwinger Equations
Yi Lu🇨🇳 · Fei Gao🇨🇳 · Yu-Xin Liu🇨🇳 · Jan M. Pawlowski🇩🇪
We study the QCD equation of state and other thermodynamic observables including the isentropic trajectories and the speed of sound. These observables are of eminent importance for the understanding of experimental results in heavy ion collisions and also provide a QCD input for studies of the timeline of heavy-ion-collisions with hydrodynamical simulations. They can be derived from the quark propagator whose gap equation is solved within a minimal approximation to the Dyson-Schwinger equations of QCD at finite temperature and density. This minimal approximation aims at a combination of computational efficiency and simplification of the truncation scheme while maintaining quantitative precision. This minimal DSE scheme is confronted and benchmarked with results for correlation functions and observables from first principles QCD lattice at vanishing density and quantitative functional approaches at finite density.
Comments:
14 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2310.18383 [pdf]
PRD(2024)·34 citations
15
[Submitted on 27 Oct 2023] (cross-list from hep-ph)
Orbital Angular Momentum at Small $x$ Revisited
Yuri V. Kovchegov🇺🇸 · Brandon Manley🇺🇸
We revisit the problem of the small Bjorken- $x$ asymptotics of the quark and gluon orbital angular momentum (OAM) distributions in the proton utilizing the revised small- $x$ helicity evolution derived recently. We relate the quark and gluon OAM distributions at small $x$ to the polarized dipole amplitudes and their (first) impact-parameter moments. To obtain the OAM distributions, we derive novel small- $x$ evolution equations for the impact-parameter moments of the polarized dipole amplitudes in the double-logarithmic approximation (summing powers of $α_{s} ln^{2} (1/ x)$ with $α_{s}$ the strong coupling constant). We solve these evolution equations numerically and extract the leading large- $N_{c}$ , small- $x$ asymptotics of the quark and gluon OAM distributions, which we determine to be \begin{align} L_{q+\bar{q}}(x, Q^2) \sim L_{G}(x,Q^2) \sim \Delta \Sigma(x, Q^2) \sim \Delta G(x,Q^2) \sim \left(\frac{1}{x}\right)^{3.66 \, \sqrt{\frac{\alpha_s N_c}{2\pi}}}, \notag \end{align} in agreement with the existing results in the literature within the precision of our numerical evaluation. (Here $N_{c}$ is the number of quark colors.) We also investigate the ratios of the quark and gluon OAM distributions to their helicity distribution counterparts in the small- $x$ region.
Comments:
36 pages, 6 figures; v2: typos corrected, references added; v3: several signs corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2310.18404 [pdf]
JHEP(2024)·29 citations
16
[Submitted on 27 Oct 2023] (cross-list from hep-th)
A loophole in the proofs of asymptotic freedom and quantum triviality
Paul Romatschke🇺🇸
In 1973, Coleman and Gross proved that in four dimensions, only non-abelian gauge theories can have asymptotic freedom. More recently, Aizenman and Duminil-Copin proved that four dimensional scalar field theories are quantum trivial in the continuum. Both of these proofs have a loophole, and it is the same loophole in both proofs: The proofs assume that the scalar self-coupling in the UV is positive definite. While this is a perfectly reasonable and classically very intuitive assumption, it is an assumption nevertheless. In this work, I show that the assumption of coupling positivity is violated in a concrete quantum field theory, the O(N) model, in the large N limit. Surprisingly, despite the classically nonsensical unbounded potential, the negative coupling has no pathological consequence for propagators, the free energy or cross sections. This suggests that interacting scalar field theories with asymptotic freedom in four dimensions are possible, despite long-held opinions to the contrary.
Comments:
10 pages, talk contribution to EPS-HEP 2023 conference
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.18414 [pdf]
PoS(2024)·6 citations
17
[Submitted on 28 Oct 2023] (cross-list from hep-ph)
On the Fractional Quark-Antiquark Confinement and Symplectic Quantum Mechanics
M. Abu-Shady🇪🇬 · R. R. Luz🇧🇷 · G. X. A. Petronilo🇧🇷 · A. E. Santana🇧🇷 · R. G. G. Amorim🇧🇷
Using the formalism of generalized fractional derivatives, a two-dimensional non-relativistic meson system is studied. The mesons are interacting by a Cornell potential. The system is formulated in the domain of the symplectic quantum mechanics by means of the generalized fractional Nikiforov-Uvarov method. The corresponding Wigner function and the energy eigenvalues are then derived. The effect of fractional parameters $α$ and $β$ with the ground state solution is analyzed through the Wigner function for the charm-anticharm, bottom-antibottom and $b c$ mesons. One of the fundamental achievements of such Cornell model is the determination of heavy quarkonia mass spectra. We have computed these masses and the
Comments:
11 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.18810 [pdf]
Int.J.Mod.Phys.A(2024)·3 citations
18
[Submitted on 28 Oct 2023] (cross-list from physics.comp-ph)
A thousand fermions in a 3D harmonic trap via Monte Carlo simulations
Siu A. Chin
By use of a special wave function derived from similarly transformed propagators, this work shows that the energy of a thousand spin-balanced fermions in a three-dimensional harmonic potential can be accurately computed using the Monte Carlo method.
Comments:
18 pages with 6 figures
Subjects:
Computational Physics (physics.comp-ph); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2310.18818 [pdf]
0 citations
19
[Submitted on 29 Oct 2023] (cross-list from hep-lat)
$T$ -matrix Analysis of Static Wilson Line Correlators from Lattice QCD at Finite Temperature
Zhanduo Tang🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Ralf Rapp🇺🇸
We utilize a previously constructed thermodynamic $T$ -matrix approach to the quark-gluon plasma (QGP) to calculate Wilson line correlators (WLCs) of a static quark-antiquark pair and apply them to the results from 2+1-flavor lattice-QCD (lQCD) computations with realistic pion mass. The self-consistent $T$ -matrix results, which include constraints from the lQCD equation of state in the light-parton sector, can describe the lQCD data for WLCs fairly well once refinements of the input parameters are implemented. In particular, the input potential requires less screening than used in previous $T$ -matrix analyses. Pertinent predictions for the spectral and transport properties of the QGP are discussed, including the spatial diffusion coefficient for heavy quarks which turns out to have a rather weak temperature dependence, in approximate agreement with recent lQCD results.
Comments:
11 pages, 10 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.18864 [pdf]
EPJA(2024)·37 citations
20
[Submitted on 29 Oct 2023] (cross-list from hep-ph)
Impact of Medium Anisotropy on Quarkonium Dissociation and Regeneration
Captain R. Singh🇮🇳 · Mohammad Yousuf Jamal🇮🇳 · Raghunath Sahoo🇮🇳
Quarkonium production in ultra-relativistic collisions plays a crucial role in probing the existence of hot QCD matter. This study explores quarkonia states dissociation and regeneration in the hot QCD medium while considering momentum anisotropy. The net quarkonia decay width ( $Γ_{D}$ ) arises from two essential processes: collisional damping and gluonic dissociation. The quarkonia regeneration includes the transition from octet to singlet states within the anisotropic medium. Our study utilizes a medium-modified potential that incorporates anisotropy via particle distribution functions. This modified potential gives rise to collisional damping for quarkonia due to the surrounding medium, as well as the transition of quarkonia from singlet to octet states due to interactions with gluons. Furthermore, we employ the detailed balance approach to investigate the regeneration of quarkonia within this medium. Our comprehensive analysis spans various temperature settings, transverse momentum values, and anisotropic strengths. Notably, we find that, in addition to medium temperatures and heavy quark transverse momentum, anisotropy significantly influences the dissociation and regeneration of various quarkonia states.
Comments:
11 pages and 4 captioned figures, same as the published version in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2310.18909 [pdf]
EPJC(2024)·9 citations
21
[Submitted on 29 Oct 2023] (cross-list from hep-ph)
Towards higher-order collinear splittings with massive partons
Prasanna K. Dhani🇪🇸 · Germán Rodrigo🇪🇸 · German F. R. Sborlini🇪🇸
The singularities associated with QCD factorization in the collinear limit are key ingredients for high-precision theoretical predictions in particle physics. They govern the collinear behaviour of scattering amplitudes, as well as the perturbative energy evolution of parton densities (PDFs) and fragmentation functions (FFs). In this talk, we present the computation of multiple collinear and higher-order QCD splittings with massive partons. Our results are highly-relevant for the consistent introduction of mass effects in the subtraction formalism and PDF/FF evolution.
Comments:
6 pages. Contribution to the Proceedings of the EPS-HEP 2023 Conference
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2310.18972 [pdf]
PoS(2024)·0 citations
22
[Submitted on 29 Oct 2023] (cross-list from hep-ph)
Studying the production mechanisms of light meson resonances in two-pion photoproduction: a Regge approach
Łukasz Bibrzycki🇵🇱 · Nadine Hammoud🇵🇱 · Vincent Mathieu🇪🇸 · Robert J. Perry🇪🇸 · Adam P. Szczepaniak🇺🇸
A calculation of the angular moments of two-pion photoproduction is presented. The underlying theoretical model encodes the prominent $ρ (770)$ resonance and the expected leading background contribution coming from the Deck mechanism. The model contains a number of free parameters which are fit to experimental data. A good description of the angular moments is obtained.
Comments:
5 pages, 3 figures. Prepared as proceedings contribution for the 20th International Conference on Hadron Spectroscopy and Structure (HADRON 2023), Genova, Italy, 5-9/6/2023
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.18990 [pdf]
Nuovo Cim.C(2024)·0 citations
23
[Submitted on 29 Oct 2023] (cross-list from hep-ph)
Nonperturbative photon $q q ˉ$ light front wave functions from a contact interaction model
Chao Shi🇨🇳 · Zhongtian Yang🇨🇳 · Xurong Chen🇨🇳 · Wenbao Jia🇨🇳 · Cuibai Luo🇨🇳 · Wenchang Xiang🇨🇳
We propose a method to calculate the $q q ˉ$ light front wave functions (LFWFs) of photon at low-virtuality, i.e., the light front amplitude of $γ^{*} \to q q ˉ$ at low $Q^{2}$ , based on a light front projection approach. We exemplify this method using a contact interaction model within Dyson-Schwinger equations formalism and obtain the nonperturbative photon $q q ˉ$ LFWFs. In this case, we find the nonperturbative effects are encoded in the enhanced quark mass and a dressing function of covariant quark-photon vertex, as compared to the leading order quantum electrodynamics photon $q q ˉ$ LFWFs. We then use nonperturbative-effect modified photon $q q ˉ$ LFWFs to study the inclusive deep inelastic scattering HERA data in the framework of the color dipole model. The results demonstrate that the theoretical description of data at low $Q^{2}$ can be significantly improved once the nonperturbative corrections are included in the photon LFWFs.
Comments:
11 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2310.19042 [pdf]
PRD(2024)·6 citations
24
[Submitted on 29 Oct 2023] (cross-list from hep-lat)
Transversity PDFs of the proton from lattice QCD with physical quark masses
Xiang Gao🇺🇸 · Andrew D. Hanlon🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Qi Shi🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸
We present a lattice QCD calculation of the transversity isovector- and isoscalar-quark parton distribution functions (PDFs) of the proton utilizing a perturbative matching at next-to-leading-order (NLO) accuracy. Additionally, we determine the isovector and isoscalar tensor charges for the proton. In both calculations, the disconnected contributions to the isoscalar matrix elements have been ignored. The calculations are performed using a single ensemble of $N_{f} = 2 + 1$ highly-improved staggered quarks simulated with physical-mass quarks and a lattice spacing of $a = 0.076$ fm. The Wilson-clover action, with physical quark masses and smeared gauge links obtained from one iteration of hypercubic smearing, is used in the valence sector. Using the NLO operator product expansion, we extract the lowest four to six Mellin moments and the PDFs via a neural network from the matrix elements in the pseudo-PDF approach. In addition, we calculate the PDFs in the quasi-PDF approach with hybrid-scheme renormalization and the recently developed leading-renormalon resummation technique, at NLO with the resummation of leading small- $x$ logarithms.
Comments:
23 pages, 22 figures, and 2 tables; version accepted for publication in PRD
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2310.19047 [pdf]
PRD(2024)·40 citations
25
[Submitted on 30 Oct 2023] (cross-list from hep-lat)
Efficient vacuum state preparation for quantum simulation of strongly interacting local quantum field theories
Thomas D. Cohen🇺🇸 · Hyunwoo Oh🇺🇸
We present an efficient approach for preparing ground states in the context of strongly interacting local quantum field theories on quantum computers. The approach produces the vacuum state in a time proportional to the square-root of the volume, which is a square-root improvement in speed compared to traditional approaches. The approach exploits a novel method for traversing the path in parameter space in which the resources scale linearly with a path length suitably defined in parameter space. Errors due to practical limitations are controlled and do not exhibit secular growth along the path. The final accuracy can be arbitrarily improved with an additive cost, which is independent of the volume and grows slower than logarithmically with the overlap between the state produced and the exact ground state. We expect that the method could potentially hold practical value not only within the realm of quantum field theories but also in addressing other challenges involving long path lengths.
Comments:
6 pages, 3 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2310.19229 [pdf]
PRA(2024)·12 citations
26
[Submitted on 30 Oct 2023] (cross-list from quant-ph)
Real-time Spin Systems from Lattice Field Theory
Neill C. Warrington🇺🇸
We construct a lattice field theory method for computing the real-time dynamics of spin systems in a thermal bath. This is done by building on previous work of Takano with Schwinger-Keldysh and functional differentiation techniques. We derive a Schwinger-Keldysh path integral for generic spin Hamiltonians, then demonstrate the method on a simple system. Our path integral has a sign problem, which generally requires exponential run time in the system size, but requires only linear storage. The latter may place this method at an advantage over exact diagonalization, which is exponential in both. Our path integral is amenable to contour deformations, a technique for reducing sign problems.
Comments:
7 pages, 2 figures, 1 table
Subjects:
Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2310.19761 [pdf]
JHEP(2023)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE