Nuclear Theory·nucl-th

Friday·July 13, 2018

14 papers—9 primary·5 cross-listed

10
$η^{'} \to η π π$ decays in unitarized resonance chiral theory
Sergi Gonzàlez-Solís🇨🇳 · Emilie Passemar🇺🇸
We study the hadronic $η^{'} \to η π π$ decays within the framework of $U (3)_{L} \otimes U (3)_{R}$ Chiral Perturbation Theory including resonance states and the complete one-loop corrections. The amplitude is projected in partial waves and unitarized by means of the $N / D$ method resumming both the important $S$ -and $D$ -wave $π π$ and the subleading $S$ -wave $π η$ final-state interactions. The participating scalar multiplet mass and coupling strengths are determined from fits to the Dalitz plot experimental data recently released by the A2 collaboration. As a byproduct of our analysis, the associated Dalitz-plot slope parameters are found to be $a = - 0.072 (7)_{stat} (8)_{syst}, b = - 0.052 (1)_{stat} (2)_{syst}, d = - 0.051 (8)_{stat} (6)_{syst}$ , which lie in the ballpark of the current experimental and theoretical determinations.
↳ hep-phhep-exnucl-thEPJC(2018)·26 citations
11
Finite-temperature equation of state of polarized fermions at unitarity
Lukas Rammelmüller🇩🇪 · Andrew C. Loheac🇺🇸 · Joaquín E. Drut🇺🇸 · Jens Braun🇩🇪
We study in a nonperturbative fashion the thermodynamics of a unitary Fermi gas over a wide range of temperatures and spin polarizations. To this end, we use the complex Langevin method, a first principles approach for strongly coupled systems. Specifically, we show results for the density equation of state, the magnetization, and the magnetic susceptibility. At zero polarization, our results agree well with state-of-the art results for the density equation of state and with experimental data. At finite polarization and low fugacity, our results are in excellent agreement with the third-order virial expansion. In the fully quantum mechanical regime close to the balanced limit, the critical temperature for superfluidity appears to depend only weakly on the spin polarization.
↳ cond-mat.quant-gashep-latnucl-thPRL(2018)·38 citations
12
Bulk Viscosity at Extreme Limits: From Kinetic Theory to Strings
Alina Czajka🇨🇦 · Keshav Dasgupta🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦 · Aalok Misra🇮🇳 · Michael Richard🇨🇦 · Karunava Sil🇮🇳
In this paper we study bulk viscosity in a thermal QCD model with large number of colors at two extreme limits: the very weak and the very strong 't Hooft couplings. The weak coupling scenario is based on kinetic theory, and one may go to the very strong coupling dynamics via an intermediate coupling regime. Although the former has a clear description in terms of kinetic theory, the intermediate coupling regime, which uses lattice results, suffers from usual technical challenges that render an explicit determination of bulk viscosity somewhat difficult. On the other hand, the very strong 't Hooft coupling dynamics may be studied using string theories at both weak and strong string couplings using gravity duals in type IIB as well as M-theory respectively. In type IIB we provide the precise fluctuation modes of the metric in the gravity dual responsible for bulk viscosity, compute the speed of sound in the medium and analyze the ratio of the bulk to shear viscosities. In M-theory, where we uplift the type IIA mirror dual of the UV complete type IIB model, we study and compare both the bulk viscosity and the sound speed by analyzing the quasi-normal modes in the system at strong IIA string coupling. By deriving the spectral function, we show the consistency of our results both for the actual values of the parameters involved as well for the bound on the ratio of bulk to shear viscosities.
↳ hep-thnucl-thJHEP(2019)·45 citations
13
Constraints on the moment of inertia of PSR J0737-3039A from GW170817
Philippe Landry🇺🇸 · Bharat Kumar🇮🇳
Continued observation of PSR J0737-3039, the double pulsar, is expected to yield a precise determination of its primary component's moment of inertia in the next few years. Since the moment of inertia depends sensitively on the neutron star's internal structure, such a measurement will constrain the equation of state of ultra-dense matter, which is believed to be universal. Independent equation-of-state constraints have already been established by the gravitational-wave measurement of the neutron-star tidal deformability in GW170817. Here, using well-known universal relations among neutron star observables, we translate the reported 90%-credible bounds on tidal deformability into a direct constraint, $I_{⋆} = 1.1 5_{- 0.24}^{+ 0.38} \times 1 0^{45} g cm^{2}$ , on the moment of inertia of PSR J0737-3039A. Should a future astrophysical measurement of $I_{⋆}$ disagree with this prediction, it could indicate a breakdown in the universality of the neutron-star equation of state.
↳ gr-qcastro-ph.HEnucl-thApJL(2018)·92 citations
14
Finite-volume spectrum of $π^{+} π^{+}$ and $π^{+} π^{+} π^{+}$ systems
Maxim Mai🇺🇸 · Michael Doring🇺🇸
The ab-initio understanding of hadronic three-body systems above threshold, such as exotic resonances or the baryon spectrum, requires the mapping of the finite-volume eigenvalue spectrum, produced in lattice QCD calculations, to the infinite volume. We present the first application of such a formalism to a physical system in form of three interacting positively charged pions. The results for the ground state energies agree with the available lattice QCD results by the NPLQCD collaboration at unphysical pion masses. Extrapolations to physical pion masses are performed using input from effective field theory. The excited energy spectrum is predicted. This demonstrates the feasibility to determine three-body amplitudes above threshold from lattice QCD, including resonance properties of axial mesons, exotics, and excited baryons.
↳ hep-lathep-phnucl-thPRL(2019)·156 citations

Affiliations

first authorsco-authorsvia INSPIRE

η′→ηππ decays in unitarized resonance chiral theory

Finite-temperature equation of state of polarized fermions at unitarity

Bulk Viscosity at Extreme Limits: From Kinetic Theory to Strings

Constraints on the moment of inertia of PSR J0737-3039A from GW170817

Finite-volume spectrum of π+π+ and π+π+π+ systems

Affiliations

$η^{'} \to η π π$ decays in unitarized resonance chiral theory

Finite-volume spectrum of $π^{+} π^{+}$ and $π^{+} π^{+} π^{+}$ systems