Nuclear Theory·nucl-th

Monday·March 18, 2019

10 papers—6 primary·4 cross-listed

07
Cool baryon and quark matter in holographic QCD
Takaaki Ishii🇯🇵 · Matti Järvinen🇳🇱 · Govert Nijs🇳🇱
We establish a holographic bottom-up model which covers both the baryonic and quark matter phases in cold and dense QCD. This is obtained by including the baryons using simple approximation schemes in the V-QCD model, which also includes the backreaction of the quark matter to the dynamics of pure Yang-Mills. We examine two approaches for homogeneous baryon matter: baryons as a thin layer of noninteracting matter in the holographic bulk, and baryons with a homogeneous bulk gauge field. We find that the second approach exhibits phenomenologically reasonable features. At zero temperature, the vacuum, baryon, and quark matter phases are separated by strongly first order transitions as the chemical potential varies. The equation of state in the baryonic phase is found to be stiff, i.e., the speed of sound clearly exceeds the value $c_{s}^{2} = 1/3$ of conformal plasmas at high baryon densities.
↳ hep-phhep-thnucl-thJHEP(2019)·90 citations
08
A complete set of in-medium splitting functions to any order in opacity
Matthew D. Sievert🇺🇸 · Ivan Vitev🇺🇸 · Boram Yoon🇺🇸
In this Letter we report the first calculation of all $O (α_{s})$ medium-induced branching processes to any order in opacity. Our splitting functions results are presented as iterative solutions to matrix equations with initial conditions set by the leading order branchings in the vacuum. The flavor and quark mass dependence of the in-medium $q \to q g$ , $g \to g g$ , $q \to g q$ , $g \to q q ˉ$ processes is fully captured by the light-front wavefunction formalism and the color representation of the parent and daughter partons. We include the explicit solutions to second order in opacity as supplementary material and present numerical results in a realistic strongly-interacting medium produced in high center-of-mass energy heavy ion collisions at the Large Hadron Collider. Our numerical simulations show that the second order in opacity corrections can change the energy dependence of the in-medium shower intensity. We further find corrections to the longitudinal and angular distributions of the in-medium splitting kernels that may have important implications for jet substructure phenomenology.
↳ hep-phnucl-thPLB(2019)·74 citations
09
Nucleon axial, scalar, and tensor charges using lattice QCD at the physical pion mass
Nesreen Hasan🇩🇪 · Jeremy Green🇩🇪 · Stefan Meinel🇺🇸 · Michael Engelhardt🇺🇸 · Stefan Krieg🇩🇪 · John Negele🇺🇸 · Andrew Pochinsky🇺🇸 · Sergey Syritsyn🇺🇸
We report on lattice QCD calculations of the nucleon isovector axial, scalar, and tensor charges. Our calculations are performed on two 2+1-flavor ensembles generated using a 2-HEX-smeared Wilson-clover action at the physical pion mass and lattice spacings $a \approx$ 0.116 and 0.093 fm. We use a wide range of source-sink separations - eight values ranging from roughly 0.4 to 1.4 fm on the coarse ensemble and three values from 0.9 to 1.5 fm on the fine ensemble - which allows us to perform an extensive study of excited-state effects using different analysis and fit strategies. To determine the renormalization factors, we use the nonperturbative Rome-Southampton approach and compare RI'-MOM and RI-SMOM intermediate schemes to estimate the systematic uncertainties. Our final results are computed in the MS-bar scheme at scale 2 GeV. The tensor and axial charges have uncertainties of roughly 4%, $g_{T} = 0.972 (41)$ and $g_{A} = 1.265 (49)$ . The resulting scalar charge, $g_{S} = 0.927 (303)$ , has a much larger uncertainty due to a stronger dependence on the choice of intermediate renormalization scheme and on the lattice spacing.
↳ hep-lathep-phnucl-thPRD(2019)·73 citations
10
Sigma models on quantum computers
Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Henry Lamm🇺🇸 · Scott Lawrence (for the NuQS Collaboration)🇺🇸
We formulate a discretization of sigma models suitable for simulation by quantum computers. Space is substituted by a lattice, as usually done in lattice field theory, while the target space (a sphere) is replaced by the "fuzzy sphere", a construction well known from non-commutative geometry. Contrary to more naive discretizations of the sphere, in this construction the exact $O (3)$ symmetry is maintained, which suggests that the discretized model is in the same universality class as the continuum model. That would allow for continuum results to be obtained for very rough discretizations of the target space as long as the space discretization is made fine enough. The cost of performing time-evolution, measured as the number of CNOT operations necessary, is $12 L T /Δ t$ , where $L$ is the number of spatial sites, $T$ the maximum time extent and $Δ t$ the time spacing.
↳ hep-latcond-mat.str-elnucl-thphysics.comp-ph+1PRL(2019)·71 citations

Affiliations

first authorsco-authorsvia INSPIRE

Cool baryon and quark matter in holographic QCD

A complete set of in-medium splitting functions to any order in opacity

Nucleon axial, scalar, and tensor charges using lattice QCD at the physical pion mass

Sigma models on quantum computers

Affiliations