Nuclear Theory·nucl-th

Monday·November 4, 2019

9 papers—4 primary·5 cross-listed

05
Radius of convergence in lattice QCD at finite $μ_{B}$ with rooted staggered fermions
Matteo Giordano🇭🇺 · Kornel Kapas🇭🇺 · Sandor D. Katz🇭🇺 · Daniel Nogradi🇭🇺 · Attila Pasztor🇭🇺
In typical statistical mechanical systems the grand canonical partition function at finite volume is proportional to a polynomial of the fugacity $e^{μ / T}$ . The zero of this Lee-Yang polynomial closest to the origin determines the radius of convergence of the Taylor expansion of the pressure around $μ = 0$ . The computationally cheapest formulation of lattice QCD, rooted staggered fermions, with the usual definition of the rooted determinant, does not admit such a Lee-Yang polynomial. We argue that the radius of convergence is then bounded by the spectral gap of the reduced matrix of the unrooted staggered operator. This is a cutoff effect that potentially affects all estimates of the radius of convergence with the standard staggered rooting. We suggest a new definition of the rooted staggered determinant at finite chemical potential that allows for a definition of a Lee-Yang polynomial, and, therefore of the numerical study of Lee-Yang zeros. We also describe an algorithm to determine the Lee-Yang zeros and apply it to configurations generated with the 2-stout improved staggered action at $N_{t} = 4$ . We perform a finite-volume scaling study of the leading Lee-Yang zeros and estimate the radius of convergence of the Taylor expansion extrapolated to an infinite volume. We show that the limiting singularity is not on the real line, thus giving a lower bound on the location of any possible phase transitions at this lattice spacing. In the vicinity of the crossover temperature at zero chemical potential, the radius of convergence turns out to be $μ_{B} / T \approx 2$ and roughly temperature independent. Our simulations are performed at strange quark chemical potential $μ_{s} = 0$ , but the method can be straightforwardly extended to strangeness chemical potential $μ_{S} = 0$ or strangeness neutrality.
↳ hep-lathep-phnucl-thPRD(2020)·50 citations
06
Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes
Jia Jie Li🇩🇪 · Armen Sedrakian🇩🇪 · Mark Alford🇺🇸
We compute the mass, radius and tidal deformability of stars containing phase transitions from hadronic to quark phase(s). These quantities are computed for three types of hadronic envelopes: purely nuclear, hyperonic, and $Δ$ -resonance--hyperon admixed matter. We consider either a single first-order phase transition to a quark phase with a maximally stiff equation of state (EOS) or two sequential first-order phase transitions mimicking a transition from hadronic to a quark matter phase followed by a second phase transition to another quark phase. We explore the parameter space which produces low-mass twin and triplet configurations where equal-mass stars have substantially different radii and tidal deformabilities. We demonstrate that while for purely hadronic stiff EOS the obtained maximum mass is inconsistent with the upper limit on this quantity placed by GW170817, the inclusion of the hyperonic and $Δ$ -resonance degrees of freedom, as well as the deconfinement phase transition at sufficiently low density, produces a configuration of stars consistent with this limit. The obtained hybrid star configurations are in the mass range relevant for the interpretation of the GW170817 event. We compare our results for the tidal deformability with the limits inferred from GW170817 showing that the onset of non-nucleonic phases, such as $Δ$ -resonance--hyperon admixed phase and/or the quark phase(s), are favored by this data if the nuclear EOS is stiff. Also, we show that low-mass twins and especially triplets proliferate the number of combinations of possible types of stars that can undergo a merger event, the maximal number being six in the case of triplets. The prospects for uncovering the first-order phase transition(s) to and in quark matter via measurements of tidal deformabilities in merger events are discussed.
↳ astro-ph.HEhep-phnucl-thPRD(2020)·73 citations
07
Dynamical grooming of QCD jets
Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Konrad Tywoniuk🇳🇴
We propose a new class of infrared-collinear (IRC) and Sudakov safe observables with an associated jet grooming technique that removes dynamically soft and large angle branches. It is based on identifying the hardest branch in the Cambridge/Aachen re-clustering sequence and discarding prior splittings that occur at larger angles. This leads to a dynamically generated cut-off on the phase space of the tagged splitting that is encoded in a Sudakov form factor. In this exploratory study we focus on the mass and momentum sharing distributions of the tagged splitting which we analyze analytically to modified leading logarithmic accuracy and compare to Monte-Carlo simulations.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·66 citations
08
Neutron rich matter in the laboratory and in the heavens after GW170817
C. J. Horowitz🇺🇸
The historic observations of the neutron star merger GW170817 advanced our understanding of r-process nucleosynthesis and the equation of state (EOS) of neutron rich matter. Simple neutrino physics suggests that supernovae are not the site of the main r-process. Instead, the very red color of the kilonova associated with GW170817 shows that neutron star (NS) mergers are an important r-process site. We now need to measure the masses and beta decay half-lives of very neutron rich heavy nuclei so that we can more accurately predict the abundances of heavy elements that are produced. This can be done with new radioactive beam accelerators such as the Facility for Rare Isotope Beams (FRIB). GW170817 provided information on the deformability of NS and the equation of state of dense matter. The PREX II experiment will measure the neutron skin of $^{208}$ Pb and help constrain the low density EOS. As the sensitivity of gravitational wave detectors improve, we expect to observe many more events. We look forward to exciting advances and surprises!
↳ astro-ph.HEnucl-thAnnals Phys.(2019)·34 citations
09
Systematically Improvable Tensor Hypercontraction: Interpolative Separable Density-Fitting for Molecules Applied to Exact Exchange, Second- and Third-Order Møller-Plesset Perturbation Theory
Joonho Lee · Lin Lin · Martin Head-Gordon
We present a systematically improvable tensor hypercontraction (THC) factorization based on interpolative separable density fitting (ISDF). We illustrate algorithmic details to achieve this within the framework of Becke's atom-centered quadrature grid. A single ISDF parameter $c_{ISDF}$ controls the tradeoff between accuracy and cost. In particular, $c_{ISDF}$ sets the number of interpolation points used in THC, $N_{IP} = c_{ISDF} \times N_{X}$ with $N_{X}$ being the number of auxiliary basis functions. In conjunction with the resolution-of-the-identity (RI) technique, we develop and investigate the THC-RI algorithms for cubic-scaling exact exchange for Hartree-Fock and range-separated hybrids (e.g., $ω$ B97X-V) and quartic-scaling second- and third-order Møller-Plesset theory (MP2 and MP3). These algorithms were evaluated over the W4-11 thermochemistry (atomization energy) set and A24 non-covalent interaction benchmark set with standard Dunning basis sets (cc-pVDZ, cc-pVTZ, aug-cc-pVDZ, and aug-cc-pVTZ). We demonstrate the convergence of THC-RI algorithms to numerically exact RI results using ISDF points. Based on these, we make recommendations on $c_{ISDF}$ for each basis set and method. We also demonstrate the utility of THC-RI exact exchange and MP2 for larger systems such as water clusters and $C_{20}$ . We stress that more challenges await in obtaining accurate and numerically stable THC factorization for wavefunction amplitudes as well as the space spanned by virtual orbitals in large basis sets and implementing sparsity-aware THC-RI algorithms.
↳ physics.chem-phnucl-thJ.Chem.Theor.Comput.(2019)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE

Radius of convergence in lattice QCD at finite μB​ with rooted staggered fermions

Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes

Dynamical grooming of QCD jets

Neutron rich matter in the laboratory and in the heavens after GW170817

Systematically Improvable Tensor Hypercontraction: Interpolative Separable Density-Fitting for Molecules Applied to Exact Exchange, Second- and Third-Order Møller-Plesset Perturbation Theory

Affiliations

Radius of convergence in lattice QCD at finite $μ_{B}$ with rooted staggered fermions