Nuclear Theory·nucl-th

Friday·May 27, 2016

13 papers—5 primary·8 cross-listed

06
[Submitted on 25 May 2016] (cross-list from hep-lat)
Monte Carlo study of real time dynamics
Andrei Alexandru🇺🇸 · Gokce Basar🇺🇸 · Paulo F. Bedaque🇺🇸 · Sohan Vartak🇺🇸 · Neill C. Warrington🇺🇸
Monte Carlo studies involving real time dynamics are severely restricted by the sign problem that emerges from highly oscillatory phase of the path integral. In this letter, we present a new method to compute real time quantities on the lattice using the Schwinger-Keldysh formalism via Monte Carlo simulations. The key idea is to deform the path integration domain to a complex manifold where the phase oscillations are mild and the sign problem is manageable. We use the previously introduced "contraction algorithm" to create a Markov chain on this alternative manifold. We substantiate our approach by analyzing the quantum mechanical anharmonic oscillator. Our results are in agreement with the exact ones obtained by diagonalization of the Hamiltonian. The method we introduce is generic and in principle applicable to quantum field theory albeit very slow. We discuss some possible improvements that should speed up the algorithm.
Comments:
5 pages, 3 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1605.08040 [pdf]
PRL(2016)·122 citations
07
[Submitted on 25 May 2016] (cross-list from hep-ph)
Analysis strategies for general spin-independent WIMP-nucleus scattering
Martin Hoferichter🇺🇸 · Philipp Klos🇩🇪 · Javier Menéndez🇯🇵 · Achim Schwenk🇩🇪
We propose a formalism for the analysis of direct-detection dark-matter searches that covers all coherent responses for scalar and vector interactions and incorporates QCD constraints imposed by chiral symmetry, including all one- and two-body WIMP-nucleon interactions up to third order in chiral effective field theory. One of the free parameters in the WIMP-nucleus cross section corresponds to standard spin-independent searches, but in general different combinations of new-physics couplings are probed. We identify the interference with the isovector counterpart of the standard spin-independent response and two-body currents as the dominant corrections to the leading spin-independent structure factor, and discuss the general consequences for the interpretation of direct-detection experiments, including minimal extensions of the standard spin-independent analysis. Fits for all structure factors required for the scattering off xenon targets are provided based on state-of-the-art nuclear shell-model calculations.
Comments:
20 pages, 7 figures; v2 includes the two-body current related to the trace anomaly of the QCD energy-momentum tensor
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1605.08043 [pdf]
PRD(2016)·121 citations
08
[Submitted on 25 May 2016] (cross-list from astro-ph.HE)
Global properties of rotating neutron stars with QCD equations of state
Tyler Gorda🇺🇸
We numerically investigate global properties of rotating neutron stars using the allowed band of QCD equations of state derived by Kurkela et al. This band is constrained by chiral effective theory at low densities and perturbative QCD at high densities, and is thus, in essence, a controlled constraint from first-principles physics. Previously, this band of equations of state was used to investigate non-rotating neutron stars only; in this work, we extend these results to any rotation frequency below the mass-shedding limit. We investigate mass--radius curves, allowed mass--frequency regions, radius--frequency curves for a typical 1.4-solar-mass star, and the values of the moment of inertia of the double pulsar PSR J0737-3039A, a pulsar whose moment of inertia may be constrained observationally in a few years. We present limits on observational data coming from these constraints, and identify values of observationally-relevant parameters that would further constrain the allowed region for the QCD equation of state. We also discuss how much this region would be constrained by a measurement of the moment of inertial of the double pulsar PSR J0737-3039A.
Comments:
5 pages, 5 figures; v2: discussion of Figure 1 updated with added references, Figure 2 updated, matches accepted journal version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.08067 [pdf]
ApJ(2016)·15 citations
09
[Submitted on 26 May 2016] (cross-list from hep-th)
Chaos in chiral condensates in gauge theories
Koji Hashimoto🇯🇵 · Keiju Murata🇯🇵 · Kentaroh Yoshida🇯🇵
Assigning a chaos index for dynamics of generic quantum field theories is a challenging problem, because the notion of Lyapunov exponent, which is useful for singling out chaotic behaviors, works only in classical systems. We address the issue by using the AdS/CFT correspondence, as the large $N_{c}$ limit provides a classicalization (other than the standard $ℏ \to 0$ ) while keeping nontrivial quantum condensation. We demonstrate the chaos in the dynamics of quantum gauge theories: Time evolution of homogeneous quark condensates $⟨ q ˉ q ⟩$ and $⟨ q ˉ γ_{5} q ⟩$ in an $N = 2$ supersymmetric QCD with the $S U (N_{c})$ gauge group at large $N_{c}$ and at large 't Hooft coupling $λ \equiv N_{c} g_{YM}^{2}$ exhibits a positive Lyapunov exponent. The chaos dominates the phase space for energy density $E ≳ (6 \times 1 0^{2}) \times m_{q}^{4} (N_{c} / λ^{2})$ where $m_{q}$ is the quark mass. We evaluate the largest Lyapunov exponent as a function of $(N_{c}, λ, E)$ and find that the $N = 2$ supersymmetric QCD is more chaotic for smaller $N_{c}$ .
Comments:
9 pages, 5 figures. v2: Analysis of Lyapunov exponent of linear sigma model added, references and a footnote added. v3: Published version. An appendix added for explaining relation between classical chaos and out-of-time-ordered correlator. Title modified, abstract refined v4: Typos and grammatical errors corrected
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); nlin.CD (nlin.CD); Nuclear Theory (nucl-th)
arXiv:
1605.08124 [pdf]
PRL(2016)·40 citations
10
[Submitted on 26 May 2016] (cross-list from hep-ph)
Exclusive vector meson production with a leading neutron in photon - hadron interactions at hadronic colliders
V.P. Goncalves🇸🇪 · B.D. Moreira🇧🇷 · F.S. Navarra🇧🇷 · D. Spiering🇧🇷
In this paper we study leading neutron production in photon - hadron interactions which take place in $pp$ and $p A$ collisions at large impact parameters. Using a model that describes the recent leading neutron data at HERA, we consider exclusive vector meson production in association with a leading neutron in $pp / p A$ collisions at RHIC and LHC energies. The total cross sections and rapidity distributions of $ρ$ , $ϕ$ and $J /Ψ$ produced together with a leading neutron are computed. Our results indicate that the study of these processes is feasible and that it can be used to improve the understanding of leading neutron processes and of exclusive vector meson production.
Comments:
8 pages, 3 figures, 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1605.08186 [pdf]
PRD(2016)·15 citations
11
[Submitted on 26 May 2016] (cross-list from hep-ph)
Magnetic properties in the inhomogeneous chiral phase
Ryo Yoshiike🇯🇵 · Kazuya Nishiyama🇯🇵 · Toshitaka Tatsumi🇯🇵
We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.
Comments:
6 pages, 3 figures, talk given in Excited QCD 2016, Mar. 6-12, 2016, Costa da Caparica, Portugal
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.08218 [pdf]
Acta Phys.Polon.Supp.(2016)·1 citation
12
[Submitted on 26 May 2016] (cross-list from hep-th)
Form Invariance, Topological Fluctuations and Mass Gap of Yang-Mills Theory
Yachao Qian🇺🇸 · Jun Nian🇫🇷
In order to have a new perspective on the long-standing problem of the mass gap in Yang-Mills theory, we study the quantum Yang-Mills theory in the presence of topologically nontrivial backgrounds in this paper. The topologically stable gauge fields are constrained by the form invariance condition and the topological properties. Obeying these constraints, the known classical solutions to the Yang-Mills equation in the 3- and 4-dimensional Euclidean spaces are recovered, and the other allowed configurations form the nontrivial topological fluctuations at quantum level. Together, they constitute the background configurations, upon which the quantum Yang-Mills theory can be constructed. We demonstrate that the theory mimics the Higgs mechanism in a certain limit and develops a mass gap at semi-classical level on a flat space with finite size or on a sphere.
Comments:
52 + 41 pages, 11 figures; v2: published version with minor changes
Subjects:
High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
1605.08425 [pdf]
Int.J.Mod.Phys.A(2019)·3 citations
13
[Submitted on 26 May 2016] (cross-list from hep-ph)
Supporting the search for the CEP location with nonlocal PNJL models constrained by Lattice QCD
Gustavo A. Contrera🇦🇷 · A. Gabriela Grunfeld🇦🇷 · David Blaschke🇵🇱
We investigate the possible location of the critical endpoint in the QCD phase diagram based on nonlocal covariant PNJL models including a vector interaction channel. The form factors of the covariant interaction are constrained by lattice QCD data for the quark propagator. The comparison of our results for the pressure including the pion contribution and the scaled pressure shift $Δ P / T^{4}$ vs $T / T_{c}$ with lattice QCD results shows a better agreement when Lorentzian formfactors for the nonlocal interactions and the wave function renormalization are considered. The strength of the vector coupling is used as a free parameter which influences results at finite baryochemical potential. It is used to adjust the slope of the pseudocritical temperature of the chiral phase transition at low baryochemical potential and the scaled pressure shift accessible in lattice QCD simulations. Our study, albeit presently performed at the meanfield level, supports the very existence of a critical point and favors its location within a region that is accessible in experiments at the NICA accelerator complex.
Comments:
7 pages, 7 Figures. Version accepted by Eur. Phys. J. A as part of the topical collection: Exploring strongly interacting matter at high densities - NICA White Paper
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1605.08430 [pdf]
EPJA(2016)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE