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Nuclear Theory·nucl-th

Friday·April 23, 2021

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    Symmetry from Entanglement Suppression

    Ian Low🇺🇸 · Thomas Mehen🇺🇸

    Symmetry is among the most fundamental and powerful concepts in nature, whose existence is usually taken as given, without explanation. We explore whether symmetry can be derived from more fundamental principles from the perspective of quantum information. Starting with a two-qubit system, we show there are only two minimally entangling logic gates: the Identity and the SWAP, where SWAP interchanges the two states of the qubits. We further demonstrate that, when viewed as an entanglement operator in the spin-space, the -matrix in the two-body scattering of fermions in the -wave channel is uniquely determined by unitarity and rotational invariance to be a linear combination of the Identity and the SWAP. Realizing a minimally entangling -matrix would give rise to global symmetries, as exemplified in Wigner's spin-flavor symmetry and Schrödinger's conformal invariance in low energy Quantum Chromodynamics. For species of qubit, the Identity gate is associated with an symmetry, which is enlarged to when there is a species-universal coupling constant.

    ↳ hep-thhep-lathep-phnucl-th+1PRD(2021)·98 citations
  2. 05

    Revisiting the compatibility problem between the gauge principle and the observability of the canonical orbital angular momentum in the Landau problem

    Masashi Wakamatsu🇯🇵 · Yoshio Kitadono🇨🇳 · Liping Zou🇨🇳 · Pengming Zhang🇨🇳

    As is widely-known, the eigen-functions of the Landau problem in the symmetric gauge are specified by two quantum numbers. The first is the familiar Landau quantum number , whereas the second is the magnetic quantum number , which is the eigen-value of the canonical orbital angular momentum (OAM) operator of the electron. The eigen-energies of the system depend only on the first quantum number , and the second quantum number does not correspond to any direct observables. This seems natural since the canonical OAM is generally believed to be a {\it gauge-variant} quantity, and observation of a gauge-variant quantity would contradict a fundamental principle of physics called the {\it gauge principle}. In recent researches, however, Bliohk et al. analyzed the motion of helical electron beam along the direction of a uniform magnetic field, which was mostly neglected in past analyses of the Landau states. Their analyses revealed highly non-trivial -dependent rotational dynamics of the Landau electron, but the problem is that their papers give an impression that the quantum number in the Landau eigen-states corresponds to a genuine observable. This compatibility problem between the gauge principle and the observability of the quantum number in the Landau eigen-states was attacked in our previous letter paper. In the present paper, we try to give more convincing answer to this delicate problem of physics, especially by paying attention not only to the {\it particle-like} aspect but also to the {\it wave-like} aspect of the Landau electron.

    ↳ quant-phhep-phnucl-thphysics.opticsAnnals Phys.(2021)·8 citations
  3. 06

    Hydrodynamic dispersion relations at finite coupling

    Sašo Grozdanov🇸🇮 · Andrei O. Starinets🇬🇧 · Petar Tadić🇮🇪

    By using holographic methods, the radii of convergence of the hydrodynamic shear and sound dispersion relations were previously computed in the supersymmetric Yang-Mills theory at infinite 't Hooft coupling and infinite number of colours. Here, we extend this analysis to the domain of large but finite 't Hooft coupling. To leading order in the perturbative expansion, we find that the radii grow with increasing inverse coupling, contrary to naive expectations. However, when the equations of motion are solved using a qualitative non-perturbative resummation, the dependence on the coupling becomes piecewise continuous and the initial growth is followed by a decrease. The piecewise nature of the dependence is related to the dynamics of branch point singularities of the energy-momentum tensor finite-temperature two-point functions in the complex plane of spatial momentum squared. We repeat the study using the Einstein-Gauss-Bonnet gravity as a model where the equations can be solved fully non-perturbatively, and find the expected decrease of the radii of convergence with the effective inverse coupling which is also piecewise continuous. Finally, we provide arguments in favour of the non-perturbative approach and show that the presence of non-perturbative modes in the quasinormal spectrum can be indirectly inferred from the analysis of perturbative critical points.

    ↳ hep-thcond-mat.str-elnucl-thJHEP(2021)·30 citations
  4. 07

    Theoretical description of the neutron beta decay in the standard model at the level of 10^{-5}

    A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnkov🇷🇺

    In the framework of the Standard Model (SM) a theoretical description of the neutron beta decay is given at the level of 10^{-5}. The neutron lifetime and correlation coefficients of the neutron beta decay for a polarized neutron, a polarized electron and an unpolarized proton are calculated at the account for i) the radiative corrections of order O(\alpha E_e/m_N) ~ 10^{-5} to Sirlin's outer and inner radiative corrections of order O(\alpha/\pi), ii) the corrections of order O(E^2_e/m^2_N) ~ 10^{-5}, caused by weak magnetism and proton recoil, and iii) Wilkinson's corrections of order 10^{-5} (Wilkinson, Nucl. Phys. A377, 474 (1982)). These corrections define the SM background of the theoretical description of the neutron beta decay at the level of 10^{-5}, which is required by experimental searches of interactions beyond the SM with experimental uncertainties of a few parts of 10^{-5}.

    ↳ hep-phnucl-exnucl-thPRD(2021)·9 citations
  5. 08

    Nambu--Jona-Lasinio model constrained by lattice QCD: thermomagnetic effects in the magnetization

    William R. Tavares🇧🇷 · Ricardo L. S. Farias🇧🇷 · Sidney S. Avancini🇧🇷 · Varese S. Timóteo🇧🇷 · Marcus B. Pinto🇧🇷 · Gastão Krein🇧🇷

    We use a three-flavor Nambu--Jona-Lasinio model to study the thermodynamics of strange quark matter under a strong magnetic field. The model Lagrangian features flavor SU(3) four-quark interactions and six-quark interactions that break the UA(1) symmetry. We incorporate thermomagnetic effects in the four-quark coupling. The model predicts magnetic catalysis at low temperatures and inverse magnetic catalysis at temperatures close to the pseudocritical temperature of the QCD transition, in agreement with lattice QCD results. We compute the pressure at the mean field level and obtain the magnetization of quark matter. We adopt the recently proposed vacuum magnetic regularization (VMR) scheme, in that divergent quark mass independent contributions are not subtracted, thereby avoiding unphysical results for the magnetization. We devote special attention to the renormalized magnetization, a projected quantity that allows for direct comparisons with lattice QCD simulations. Our results are in very good agreement with lattice data indicating a paramagnetic behavior for quark matter.

    ↳ hep-phhep-latnucl-thEPJA(2021)·23 citations
  6. 09

    Resolving conclusions about the early Universe requires accurate nuclear measurements

    Cyril Pitrou🇫🇷 · Alain Coc🇫🇷 · Jean-Philippe Uzan🇫🇷 · Elisabeth Vangioni🇫🇷

    Nuclear physics experiments give reaction rates that, via modelling and comparison with primordial abundances, constrain cosmological parameters. The error bars of a key reaction, \dpg, were tightened in 2020, bringing to light discrepancies between different analyses and calling for more accurate measurements of other reactions.

    ↳ astro-ph.COnucl-thNature Rev.Phys.(2021)·42 citations

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first authorsco-authorsvia INSPIRE