Nuclear Theory·nucl-th

Tuesday·August 9, 2022

16 papers—6 primary·10 cross-listed

07
[Submitted on 5 Aug 2022] (cross-list from cond-mat.quant-gas)
Bulk viscosity of resonantly interacting fermions in the quantum virial expansion
Keisuke Fujii · Tilman Enss
We consider two-component fermions with a zero-range interaction both in two and three dimensions and calculate the bulk viscosity for an arbitrary scattering length in the high-temperature regime. We evaluate the Kubo formula for the bulk viscosity using an expansion with respect to the fugacity, which acts as a small parameter at high temperatures. In the zero-frequency limit of the Kubo formula, pinch singularities emerge that reduce the order of the fugacity by one. These singularities can turn higher-order vertex corrections at nonzero frequencies into the leading order at zero frequency, so that all such contributions have to be resummed. We present an exact microscopic computation for the bulk viscosity in the high-temperature regime by taking into account these pinch singularities. For negative scattering lengths, we derive the complete bulk viscosity at second order in fugacity and show that a self-consistent equation to resum the vertex corrections is identical to a linearized kinetic equation. For positive scattering lengths, a new type of pinch singularity arises for bound pairs. We show that the pinch singularity for bound pairs leads to a first-order contribution to the bulk viscosity, which is one order lower than that for negative scattering lengths, and that the vertex corrections also provide first-order contributions. We propose a new kinetic equation for bound pairs that derives from a self-consistent equation to resum the vertex corrections.
Comments:
27 pages, 11 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2208.03353 [pdf]
Annals Phys.(2023)·10 citations
08
[Submitted on 6 Aug 2022] (cross-list from hep-th)
Nonperturbative Casimir effects: Vacuum structure, Confinement, and Chiral Symmetry Breaking
Alexander Molochkov🇷🇺
The review of vacuum and matter restructuring in space-time with boundaries is presented. We consider phase properties of confining gauge theories and strongly interacting fermion systems. In particular, the chiral and deconfinement phase transitions properties in the presence of Casimir plates. We also discuss mass scale shifts in such systems and their possible dynamical and geometrical nature.
Comments:
12 pages, 8 figures; to appear in the Proceedings of Nobel Symposium 167: "Chiral Matter", Stockholm, June 2021
Subjects:
High Energy Physics — Theory (hep-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2208.03457 [pdf]
2 citations
09
[Submitted on 7 Aug 2022] (cross-list from cond-mat.quant-gas)
Stability against three-body clustering in one-dimensional spinless p-wave fermions
Yixin Guo · Hiroyuki Tajima
We theoretically investigate in-medium two- and three-body correlations in one-dimensional spinless fermions with attractive two-body p-wave interaction. By investigating the variational problem of two- and three-body states above the Fermi sea, we elucidate the fate of the in-medium two- and three-body cluster states. The one-dimensional system with the strong p-wave interaction is found to be stable against the formation of three-body clusters even in the presence of the Fermi sea, in contrast to higher-dimensional systems that suffer the strong three-body loss associated with the trimer formation.
Comments:
10 pages, 5 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
2208.03654 [pdf]
PRA(2022)·8 citations
10
[Submitted on 7 Aug 2022] (cross-list from cond-mat.other)
Exact factorization of the many-body Green's function theory of electrons and nuclei
Ville J. Härkönen
We combine the recently developed many-body Green's function theory for electrons and nuclei with the exact factorization of the wave function. The existing Born-Oppenheimer Green's functions are shown to be special cases of our exact approach. We consider the limitations of the laboratory frame formulation of the Green's function theory and discuss why the body-fixed frame formulation is needed in order to go beyond the Born-Oppenheimer theory. We give exact forms of the electronic and nuclear Green's functions written in terms of the exact factorized states, providing a systematic approach beyond the Born-Oppenheimer approximation. The lowest order approximation to the exact electronic Green's function is found to be an expected value of the Born-Oppenheimer electronic Green's function with respect to the nuclear density.
Comments:
11 pages, 1 Figure
Subjects:
cond-mat.other (cond-mat.other); Nuclear Theory (nucl-th)
arXiv:
2208.03730 [pdf]
PRB(2022)·3 citations
11
[Submitted on 7 Aug 2022] (cross-list from hep-ph)
Neutron-Mirror-Neutron Oscillation and Neutron Star Cooling
Itzhak Goldman🇮🇱 · Rabindra N. Mohapatra🇺🇸 · Shmuel Nussinov🇮🇱 · Yongchao Zhang🇨🇳
It was pointed out in a recent paper that the observed cooling rate of old, cold neutron stars (NS) can provide an upper limit on the transition rate of neutron to mirror neutron ( $n - n^{'}$ ). This limit is so stringent that it would preclude any discovery of $n \to n^{'}$ oscillation in the current round of terrestrial searches for the process. Motivated by this crucially important conclusion, we critically analyze this suggestion and note an interesting new effect present in nearly exact mirror models for $n \to n^{'}$ oscillation, which significantly affect this bound. The new element is the $β$ decay $n^{'} \to p^{'} + e^{'} + ν ˉ_{e}^{'}$ , which creates a cloud of mirror particles $n^{'}$ , $p^{'}$ , $e^{'}$ and $D^{'}$ inside the NS core. The $e^{'}$ can "rob" the energy generated by the $n \to n^{'}$ transition via $e - e^{'}$ scattering enabled by the presence of a (minute) milli-charge in mirror particles. This energy is emitted as unobserved mirror photons via fast mirror bremsstrahlung leading to a relaxation of this upper limit.
Comments:
5 pages + supplemental material, 1 figure, short version of arXiv:2203.08473
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2208.03771 [pdf]
PRL(2022)·15 citations
12
[Submitted on 7 Aug 2022] (cross-list from hep-ph)
Pion inspired by QCD: Nakanishi and Light-Front Integral Representations
R.M. Moita🇧🇷 · J.P.B.C. de Melo🇧🇷 · T. Frederico🇧🇷 · W. de Paula🇧🇷
The pion structure in Minkowski space is explored using the Nakanishi integral representation. A general framework is developed for the pion Bethe-Salpeter amplitude based on the Kallen-Lehmann representation of the dressed quarks with an ansatz for the pseudo-scalar $π - q q ˉ$ vertex fulfilling the axial Ward-Takahashi identity. The Nakanishi weight functions are derived for the scalar amplitudes associated with the decomposition of the pion Bethe-Salpeter amplitude in different operator bases in the Dirac spinor space in terms of the involved spectral densities. The approach is applied to an analytical model of the pion Bethe-Salpeter amplitude, which is combined with Landau gauge lattice QCD results for the quark running mass at space-like momentum. From the Nakanishi integral representation several pion observables were calculated, such as the decay constant, the spin decomposition of the valence probabilities, longitudinal and transverse momentum distributions from the valence component of the light-front wave function.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2208.03845 [pdf]
PRD(2022)·5 citations
13
[Submitted on 8 Aug 2022] (cross-list from hep-ph)
Fate of the first-order chiral phase transition in QCD: Implications for dark QCD studied via a Nambu-Jona-Lasinio model
Yuanyuan Wang🇨🇳 · Mamiya Kawaguchi🇨🇳 · Shinya Matsuzaki🇨🇳 · Akio Tomiya🇯🇵
The first-order nature of the chiral phase transition in QCD-like theories can play crucial roles to address a dark side of the Universe, where the created out-of equilibrium is essential to serve as cosmological and astrophysical probes such as gravitational wave productions, which have extensively been explored. This interdisciplinary physics is built based on a widely-accepted conjecture that the thermal chiral phase transition in QCD-like theories with massless (light) three flavors is of first order. We find that such a first order feature may not hold, when ordinary or dark quarks are externally coupled to a weak enough background field of photon or dark photon (which we collectively call a ``magnetic" field). We assume that a weak ``magnetic" background field could be originated from some ``magnetogenesis" in the early Universe. We work on a Nambu-Jona-Lasinio model which can describe the chiral phase transition in a wide class of QCD-like theories. We show that in the case with massless (light) three flavors, the first-order feature goes away when $2 f_{π}^{2} ≲ e B (≪ (4 π f_{π})^{2})$ , where $e B$ is the ``magnetic" field strength and $f_{π}$ the pion decay constant at the vacuum. This disappearance is the generic consequence of the presence of the ``magnetically" induced scale anomaly and the ``magnetic" catalysis for the chiral symmetry breaking, and would impact or constrain modeling dark QCD coupled to an external ``magnetic" field.
Comments:
23 pages, 6 figures; references added; version published in Phys.Rev.D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2208.03975 [pdf]
PRD(2022)·4 citations
14
[Submitted on 8 Aug 2022] (cross-list from astro-ph.HE)
Fast neutrino cooling in the accreting neutron star MXB 1659-29
Melissa Mendes · Farrukh J. Fattoyev · Andrew Cumming · Charles Gale
Modelling of crust heating and cooling across multiple accretion outbursts of the low mass X-ray binary MXB 1659-29 indicates that the neutrino luminosity of the neutron star core is consistent with direct Urca reactions occurring in $\sim 1%$ of the core volume. We investigate this scenario with neutron star models that include a detailed equation of state parametrized by the slope of the nuclear symmetry energy $L$ , and a range of neutron and proton superfluid gaps. We find that the predicted neutron star mass depends sensitively on $L$ and the assumed gaps. We discuss which combinations of superfluid gaps reproduce the inferred neutrino luminosity. Larger values of $L ≳ 80 MeV$ require superfluidity to suppress dUrca reactions in low mass neutron stars, i.e. that the proton or neutron gap is sufficiently strong and extends to high enough density. However, the largest gaps give masses near the maximum mass, making it difficult to accommodate colder neutron stars. We consider models with reduced dUrca normalization as an approximation of alternative, less efficient, fast cooling processes in exotic cores. We find solutions with a larger emitting volume, providing a more natural explanation for the observed neutrino luminosity, provided the fast cooling process is within a factor of $\sim 1000$ of dUrca. The heat capacities of our models span the range from fully-paired to fully-unpaired nucleons meaning that long term observations of core cooling could distinguish between models. We discuss the impact of future constraints on neutron star mass, radius and the density dependence of the symmetry energy.
Comments:
v2: 16 pages, 12 figures. Section 4 now summarized in section 5.2 and added expanded discussion of uncertainty modelling. Accepted for publication in the Astrophysical Journal
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2208.04262 [pdf]
ApJ(2022)·13 citations
15
[Submitted on 8 Aug 2022] (cross-list from astro-ph.HE)
Degeneracy in the inference of phase transitions in the neutron star equation of state from gravitational wave data
Carolyn A. Raithel🇺🇸 · Elias R. Most🇺🇸
Gravitational wave (GW) detections of binary neutron star inspirals will be crucial for constraining the dense matter equation of state (EoS). We demonstrate a new degeneracy in the mapping from tidal deformability data to the EoS, which occurs for models with strong phase transitions. We find that there exists a new family of EoS with phase transitions that set in at different densities and that predict neutron star radii that differ by up to ~500m, but that produce nearly identical tidal deformabilities for all neutron star masses. Next generation GW detectors and advances in nuclear theory may be needed to resolve this degeneracy.
Comments:
Revised version; accepted by PRL
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2208.04294 [pdf]
PRL(2023)·37 citations
16
[Submitted on 8 Aug 2022] (cross-list from astro-ph.HE)
Tidal Deformability Doppelgangers: Implications of a low-density phase transition in the neutron star equation of state
Carolyn A. Raithel🇺🇸 · Elias R. Most🇺🇸
Studying the properties of ultra-dense matter is one of the key goals of modern neutron star research. The measurement of the tidal deformability from the inspiral of a binary neutron star merger offers one promising method for constraining the equation of state (EoS) of cold, dense matter. In this work, we report on a new class of EoSs which have significantly different pressures at nuclear densities and large differences in stellar radii, but that predict surprisingly similar tidal deformabilities across the entire range of astrophysically-observed neutron star masses. Using a survey of 5 million piecewise polytropic EoSs, subject to five different sets of nuclear priors, we demonstrate that these "tidal deformability doppelgangers" occur generically. We find that they can differ substantially in the pressure (by up to a factor of 3 at nuclear densities) and in the radius of intermediate-mass neutron stars (by up to 0.5 km), but are observationally indistinguishable in their tidal deformabilities ( $ΔΛ < 30$ ) with the sensitivity of current gravitational wave detectors. We demonstrate that this near-degeneracy in the tidal deformability is a result of allowing for a phase transition at low densities. We show that a combination of input from nuclear theory (e.g., from chiral effective field theory), X-ray observations of neutron star radii, and/or the next generation of gravitational wave detectors will be able to significantly constrain these tidal deformability doppelgangers.
Comments:
Accepted in PRD
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2208.04295 [pdf]
PRD(2023)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE