Nuclear Theory·nucl-th

Wednesday·July 19, 2017

10 papers—5 primary·5 cross-listed

06
[Submitted on 17 Jul 2017] (cross-list from hep-ph)
Thermal excitation spectrum from entanglement in an expanding quantum string
Jürgen Berges🇩🇪 · Stefan Floerchinger🇩🇪 · Raju Venugopalan🇺🇸
A surprising result in $e^{+} e^{-}$ collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time $τ$ , we show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_{τ} = ℏ/ (2 π k_{B} τ)$ , even in the absence of any scatterings.
Comments:
5 pages, 3 figures, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1707.05338 [pdf]
PLB(2018)·74 citations
07
[Submitted on 18 Jul 2017] (cross-list from hep-ph)
Tachyonic instability of the scalar mode prior to QCD critical point based on Functional renormalization-group method
Takeru Yokota🇯🇵 · Teiji Kunihiro🇯🇵 · Kenji Morita🇯🇵
We establish and elucidate the physical meaning of the appearance of an acausal mode in the sigma mesonic channel, found in the previous work by the present authors, when the system approaches the $Z_{2}$ critical point. The functional renormalization group method is applied to the two--flavor quark--meson model with varying current quark mass $m_{q}$ even away from the physical value at which the pion mass is reproduced. We first determine the whole phase structure in the three-dimensional space $(T, μ, m_{q})$ consisting of temperature $T$ , quark chemical potential $μ$ and $m_{q}$ , with the tricritical point, $O (4)$ and $Z_{2}$ critical lines being located; they altogether make a wing-like shape quite reminiscent of those known in the condensed matters with a tricritical point. We then calculate the spectral functions $ρ_{σ, π} (ω, p)$ in the scalar and pseudoscalar channel around the critical points. We find that the sigma mesonic mode becomes tachyonic with a superluminal velocity at finite momenta before the system reaches the $Z_{2}$ point from the lower density, even for $m_{q}$ smaller than the physical value. One of the possible implications of the appearance of such a tachyonic mode at finite momenta is that the assumed equilibrium state with a uniform chiral condensate is unstable toward a state with an inhomogeneous $σ$ condensate. No such an anomalous behavior is found in the pseudoscalar channel. We find that the $σ$ -to- $2 σ$ coupling due to finite $m_{q}$ play an essential role for the drastic modification of the spectral function.
Comments:
13 pages, 9 figures, 4 tables, v2: references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1707.05520 [pdf]
PRD(2017)·26 citations
08
[Submitted on 18 Jul 2017] (cross-list from hep-ph)
Symmetric cumulants as a probe of the proton substructure at LHC energies
Javier L. Albacete🇪🇸 · Hannah Petersen🇩🇪 · Alba Soto-Ontoso🇪🇸
We present a systematic study of the normalized symmetric cumulants, NSC(n,m), at the eccentricity level in proton-proton interactions at $s = 13$ TeV within a wounded hot spot approach. We focus our attention on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, on this observable. We notice that the presence of short-range repulsive correlations between the hot spots systematically decreases the values of NSC(2,3) and NSC(2,4) in mid-to-ultra central collisions while increases them in peripheral interactions. In the case of NSC(2,3) we find that, as suggested by data, an anti-correlation of $ε_{2}$ and $ε_{3}$ in ultra-central collisions, i.e. NSC(2,3) $< 0$ , is possible within the correlated scenario while it never occurs without correlations. We attribute this fact to the decisive role of correlations on enlarging the probability of interaction topologies that reduce the value of NSC(2,3) and, eventually, make it negative. Further, we explore the dependence of our conclusions on the values of the hot spot radius and the repulsive core distance. Our results add evidence to the idea that considering spatial correlations between the subnucleonic degrees of freedom of the proton may have a strong impact on the initial state properties of proton-proton interactions [1].
Comments:
9 pages, 8 figures. New section on the number of subnucleonic constituents of the proton added. Accepted for publication in PLB
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1707.05592 [pdf]
PLB(2018)·35 citations
09
[Submitted on 18 Jul 2017] (cross-list from hep-lat)
Meson masses in electromagnetic fields with Wilson fermions
Gunnar S. Bali🇩🇪 · Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Benjamin Glaessle🇩🇪
We determine the light meson spectrum in QCD in the presence of background magnetic fields using quenched Wilson fermions. Our continuum extrapolated results indicate a monotonous reduction of the connected neutral pion mass as the magnetic field grows. The vector meson mass is found to remain nonzero, a finding relevant for the conjectured $ρ$ -meson condensation at strong magnetic fields. The continuum extrapolation was facilitated by adding a novel magnetic field-dependent improvement term to the additive quark mass renormalization. Without this term, sizable lattice artifacts that would deceptively indicate an unphysical rise of the connected neutral pion mass for strong magnetic fields are present. We also investigate the impact of these lattice artifacts on further observables like magnetic polarizabilities and discuss the magnetic field-induced mixing between $ρ$ -mesons and pions. We also derive Ward-Takashi identities for QCD+QED both in the continuum formulation and for (order $a$ -improved) Wilson fermions.
Comments:
32 pages, 22 figures; v2: revtex4 format, updated references, extended discussions, included study of finite size effects, conclusions unchanged; v3: improved discussions on crucial points, conclusions unchanged, new version to match published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1707.05600 [pdf]
PRD(2018)·149 citations
10
[Submitted on 18 Jul 2017] (cross-list from cond-mat.quant-gas)
Saturation properties of helium drops from a Leading Order description
A. Kievsky · A. Polls · B. Juliá-Díaz · N. K. Timofeyuk
Saturation properties are directly linked to the short-range scale of the two-body interaction of the particles. The case of helium is particular, from one hand the two-body potential has a strong repulsion at short distances. On the other hand, the extremely weak binding of the helium dimer locates this system very close to the unitary limit allowing for a description based on an effective theory. At leading order of this theory a two- and a three-body term appear, each one characterized by a low energy constant. In a potential model this description corresponds to a soft potential model with a two-body term purely attractive plus a three-body term purely repulsive constructed to describe the dimer and trimer binding energies. Here we analyse the capability of this model to describe the saturation properties making a direct link between the low energy scale and the short-range correlations. We will show that the energy per particle, $E_{N} / N$ , can be obtained with reasonable accuracy at leading order extending the validity of this approximation, characterizing universal behavior in few-boson systems close to the unitary limit, to the many-body system.
Comments:
5 pages, 3 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1707.05628 [pdf]
PRA(2017)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE

Thermal excitation spectrum from entanglement in an expanding quantum string

Tachyonic instability of the scalar mode prior to QCD critical point based on Functional renormalization-group method

Symmetric cumulants as a probe of the proton substructure at LHC energies

Meson masses in electromagnetic fields with Wilson fermions

Saturation properties of helium drops from a Leading Order description

Affiliations