Nuclear Theory·nucl-th

Tuesday·December 8, 2020

16 papers—7 primary·9 cross-listed

08
Retarded Green's Function from Rotating AdS Black Holes: Emergent CFT $_{2}$ and Viscosity
Jun Nian🇺🇸 · Leopoldo A. Pando Zayas🇺🇸
Using the AdS/CFT correspondence we consider the retarded Green's function in the background of rotating near-extremal AdS $_{4}$ black holes. Following the canonical AdS/CFT dictionary into the asymptotic boundary we get a CFT $_{3}$ result. We also take a new route and zoom in on the near-horizon region, blow up this region and show that it yields a CFT $_{2}$ result. We argue that the decoupling of the near-horizon region is akin to the decoupling of the near-throat region of a D3-brane, which led to the original formulation of the AdS/CFT correspondence, thus implying that the Kerr/CFT correspondence follows as a decoupling of the standard AdS/CFT correspondence applied to rotating black holes. As a byproduct, we compute the shear viscosity to entropy density ratio for the strongly coupled boundary CFT $_{3}$ , and find that it violates the $1/ (4 π)$ bound.
↳ hep-thgr-qcnucl-thPRD(2021)·4 citations
09
Left-right symmetry and electric dipole moments. A global analysis
Michael J. Ramsey-Musolf🇨🇳 · Juan Carlos Vasquez🇺🇸
We perform a global fit using results of searches for electric dipole moments (EDM) of diamagnetic systems within the context of the minimal left-right symmetric model. In this way, we disentangle the new "left-right" electroweak and $θ ˉ$ contributions that cannot be separated using a single EDM system. Although the fit is done for a specific model, the approach can be applied to any particle physics model. Finally, we revisit the constraint on the $D$ coefficient in $β$ -decay and find that current EDM bounds do not preclude observation of this T-violating effect in a possible next generation $β$ -decay experiment.
↳ hep-phnucl-thPLB(2021)·21 citations
10
Real-time dynamics of Chern-Simons fluctuations near a critical point
Kazuki Ikeda🇯🇵 · Dmitri E. Kharzeev🇺🇸 · Yuta Kikuchi🇺🇸
The real-time topological susceptibility is studied in $(1 + 1)$ -dimensional massive Schwinger model with a $θ$ -term. We evaluate the real-time correlation function of electric field that represents the topological Chern-Pontryagin number density in $(1 + 1)$ dimensions. Near the parity-breaking critical point located at $θ = π$ and fermion mass $m$ to coupling $g$ ratio of $m / g \approx 0.33$ , we observe a sharp maximum in the topological susceptibility. We interpret this maximum in terms of the growth of critical fluctuations near the critical point, and draw analogies between the massive Schwinger model, QCD near the critical point, and ferroelectrics near the Curie point.
↳ hep-phhep-latnucl-thquant-phPRD(2021)·37 citations
11
The energy-momentum tensor at the earliest stage of relativistic heavy ion collisions
Margaret E. Carrington🇨🇦 · Alina Czajka🇵🇱 · Stanislaw Mrowczynski🇵🇱
Nuclear collisions at high energies produce a gluon field that can be described using the Colour Glass Condensate (CGC) effective theory at proper times $τ ≲ 1$ fm/c. The theory can be used to calculate the gluon energy-momentum tensor, which provides information about the early time evolution of the chromo-electric and chromo-magnetic fields, energy density, longitudinal and transverse pressures, and other quantities. We obtain an analytic expression for the energy-momentum tensor using an expansion in the proper time, and working to sixth order. The calculation is technically difficult, in part because the number of terms involved grows rapidly with the order of the $τ$ expansion, but also because of several subtle issues related to the definition of event-averaged correlators, the method chosen to regulate these correlators, and the dependence of results on the parameters introduced by the regularization and nuclear density profile functions. All of these issues are crucially related to the important question of the extent to which we expect a CGC approach to be able to accurately describe the early stages of a heavy ion collision. We present some results for the evolution of the energy density and the longitudinal and transverse pressures. We show that our calculation gives physically meaningful results up to values of the proper time which are close to the regime at which hydrodynamic simulations are initialized. In a companion paper [1] we give a detailed analysis of several other experimentally relevant quantities that can be calculated from the energy-momentum tensor.
↳ hep-phnucl-thEPJA(2022)·32 citations
12
Unpolarized Quark and Gluon TMD PDFs and FFs at N $^{3}$ LO
Ming-xing Luo🇨🇳 · Tong-Zhi Yang🇨🇭 · Hua Xing Zhu🇨🇳 · Yu Jiao Zhu🇨🇳
In this paper we calculate analytically the perturbative matching coefficients for unpolarized quark and gluon Transverse-Momentum-Dependent (TMD) Parton Distribution Functions (PDFs) and Fragmentation Functions (FFs) through Next-to-Next-to-Next-to-Leading Order (N $^{3}$ LO) in QCD. The N $^{3}$ LO TMD PDFs are calculated by solving a system of differential equation of Feynman and phase space integrals. The TMD FFs are obtained by analytic continuation from space-like quantities to time-like quantities, taking into account the probability interpretation of TMD PDFs and FFs properly. The coefficient functions for TMD FFs exhibit double logarithmic enhancement at small momentum fraction $z$ . We resum such logarithmic terms to the third order in the expansion of $α_{s}$ . Our results constitute important ingredients for precision determination of TMD PDFs and FFs in current and future experiments.
↳ hep-phnucl-thJHEP(2021)·127 citations
13
Parton energy loss in a hard-soft factorized approach
Tianyu Dai🇺🇸 · Jean-François Paquet🇺🇸 · Derek Teaney🇺🇸 · Steffen A. Bass🇺🇸
An energetic parton travelling through a quark-gluon plasma loses energy via occasional hard scatterings and frequent softer interactions. Whether or not these interactions admit a perturbative description, the effect of the soft interactions can be factorized and encoded in a small number of transport coefficients. In this work, we present a hard-soft factorized parton energy loss model which combines a stochastic description of soft interactions and rate-based modelling of hard scatterings. We introduce a scale to estimate the regime of validity of the stochastic description, allowing for a better understanding of the model's applicability at small and large coupling. We study the energy and fermion-number cascade of energetic partons as an application of the model.
↳ hep-phnucl-thPRC(2022)·18 citations
14
Cooper Triples in Attractive Three-Component Fermions: Implication for Hadron-Quark Crossover
Hiroyuki Tajima🇯🇵 · Shoichiro Tsutsui🇯🇵 · Takahiro M. Doi🇯🇵 · Kei Iida🇯🇵
We investigate many-body properties of equally populated three-component fermions with attractive three-body contact interaction in one dimension. A diagrammatic approach suggests the possible occurrence of Cooper triples at low temperature, which are three-body counterparts of Cooper pairs with a two-body attraction. We develop a minimal framework that bridges the crossover from tightly-bound trimers to Cooper triples with increasing chemical potential and show how the formation of Cooper triples occurs in the grand-canonical phase diagram. Moreover, we argue that this non-trivial crossover is similar to the hadron-quark crossover proposed in dense matter. A coexistence of medium-induced triples and the underlying Fermi sea at positive chemical potential is analogous to quarkyonic matter consisting of baryonic excitations and the underlying quark Fermi sea. The comparison with the existing quantum Monte Carlo results implies that the emergence of these kinds of three-body states can be a microscopic origin of the peak of the sound velocity along the crossover.
↳ cond-mat.quant-gascond-mat.str-elhep-phnucl-thPRResearch(2022)·27 citations
15
Probes of the quark-gluon plasma and plasma instabilities
Sigtryggur Hauksson🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Penetrating probes in heavy-ion collisions, like jets and photons, are sensitive to the transport coefficients of the produced quark-gluon plasma, such as shear and bulk viscosity. Quantifying this sensitivity requires a detailed understanding of photon emission and jet-medium interaction in a non-equilibrium plasma. Up to now, such an understanding has been hindered by plasma instabilities which arise out of equilibrium and lead to spurious divergences when evaluating the rate of interaction of hard probes with the plasma. In this paper, we show that taking into account the time evolution of an unstable plasma cures these divergences. We calculate the time evolution of gluon two-point correlators in a setup with small initial momentum anisotropy and show that the gluon occupation density grows exponentially at early times. Based on this calculation, we argue for a phenomenological prescription where instability poles are subtracted. Finally, we show that in the Abelian case instability fields do not affect medium-induced photon emission to our order of approximation.
↳ hep-phnucl-thPRC(2021)·17 citations
16
Emergence of N-body tunable interactions in universal few-atom system
Marcelo T. Yamashita · Tobias Frederico · Lauro Tomio
A three-atom molecule AAB, formed by two identical bosons A and a distinct one B, is studied by considering coupled channels close to a Feshbach resonance. It is assumed that the subsystems AB and AA have, respectively, one and two channels, where, in this case, AA has open and closed channels separated by an energy gap. The induced three-body interaction appearing in the single channel description is derived using the Feshbach projection operators for the open and closed channels. An effective three-body interaction is revealed in the limit where the trap setup is tuned to vanishing scattering lengths . The corresponding homogeneous coupled Faddeev integral equations are derived in the unitarity limit. The s-wave transition matrix for the AA subsystem is obtained with a zero-range potential by a subtractive renormalization scheme with the introduction of two finite parameters, besides the energy gap. The effect of the coupling between the channels in the coupled equations is identified with the energy gap, which essentially provides an ultraviolet scale that competes with the van der Waals radius - this sets the short-range physics of the system in the open channel. The competition occurring at short distances exemplifies the violation of the ``van der Waals universality" for narrow Feshbach resonances in cold atomic setups. In this sense, the active role of the energy gap drives the short-range three-body physics.
↳ physics.atom-phcond-mat.quant-gasnucl-thBraz.J.Phys.(2021)·2 citations

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