Symmetry Energy I: Semi-Infinite Matter

Energy for a nucleus is considered in macroscopic limit, in terms of nucleon numbers. Further considered for a nuclear system is the Hohenberg-Kohn energy functional, in terms of proton and neutron densities. Finally, Skyrme-Hartree-Fock calculations are carried out for a half-infinite particle-stable nuclear-matter. In each case, the attention is focused on the role of neutron-proton asymmetry and on the nuclear symmetry energy. We extend the considerations on the symmetry term from an energy formula to the respective term in the Hohenberg-Kohn functional. We show, in particular, that in the limit of an analytic functional, and subject to possible Coulomb corrections, it is possible to construct isoscalar and isovector densities out of the proton and neutron densities, that retain a universal relation to each other, approximately independent of asymmetry. In the so-called local approximation, the isovector density is inversely proportional to the symmetry energy in uniform matter at the local isoscalar density. Generalized symmetry coefficient of a nuclear system is related, in the analytic limit of a functional, to an integral of the isovector density. We test the relations, inferred from the Hohenberg-Kohn functional, in the Skyrme-Hartree-Fock calculations of half-infinite matter. Within the calculations, we obtain surface symmetry coefficients and parameters characterizing the densities, for the majority of Skyrme parameterizations proposed in the literature. The volume-to-surface symmetry-coefficient ratio and the displacement of nuclear isovector relative to isoscalar surfaces both strongly increase as the slope of symmetry energy in the vicinity of normal density increases.Comment: 87 pages, 18 figures; discussion of Kohn-Sham method added, comparison to results in literature broadene

Symmetry Energy II: Isobaric Analog States

Using excitation energies to isobaric analog states (IAS) and charge invariance, we extract nuclear symmetry coefficients, from a mass formula, on a nucleus-by-nucleus basis. Consistently with charge invariance, the coefficients vary weakly across an isobaric chain. However, they change strongly with nuclear mass and range from a_a~10 MeV at mass A~10 to a_a~22 MeV at A~240. Following the considerations of a Hohenberg-Kohn functional for nuclear systems, we determine how to find in practice the symmetry coefficient using neutron and proton densities, even when those densities are simultaneously affected by significant symmetry-energy and Coulomb effects. These results facilitate extracting the symmetry coefficients from Skyrme-Hartree-Fock (SHF) calculations, that we carry out using a variety of Skyrme parametrizations in the literature. For the parametrizations, we catalog novel short-wavelength instabilities. In comparing the SHF and IAS results for the symmetry coefficients, we arrive at narrow (+-2.4 MeV) constraints on the symmetry energy values S(rho) at 0.04<rho<0.13 fm^-3. Towards normal density the constraints significantly widen, but the normal value of energy a_a^V and the slope parameter L are found to be strongly correlated. To narrow the constraints, we reach for the measurements of asymmetry skins and arrive at a_a^V=(30.2-33.7) MeV and L=(35-70) MeV, with those values being again strongly positively correlated along the diagonal of their combined region. Inclusion of the skin constraints allows to narrow the constraints on S(rho), at 0.04<rho<0.13 fm^-3, down to +-1.1 MeV. Several microscopic calculations, including variational, Bruckner-Hartree-Fock and Dirac-Bruckner-Hartree-Fock, are consistent with our constraint region on S(rho).Comment: 101 pages, 27 figures, 2 tables; submitted to Nuclear Physics

Diversification of importin-α isoforms in cellular trafficking and disease states.

The human genome encodes seven isoforms of importin α which are grouped into three subfamilies known as α1, α2 and α3. All isoforms share a fundamentally conserved architecture that consists of an N-terminal, autoinhibitory, importin-β-binding (IBB) domain and a C-terminal Arm (Armadillo)-core that associates with nuclear localization signal (NLS) cargoes. Despite striking similarity in amino acid sequence and 3D structure, importin-α isoforms display remarkable substrate specificity in vivo. In the present review, we look at key differences among importin-α isoforms and provide a comprehensive inventory of known viral and cellular cargoes that have been shown to associate preferentially with specific isoforms. We illustrate how the diversification of the adaptor importin α into seven isoforms expands the dynamic range and regulatory control of nucleocytoplasmic transport, offering unexpected opportunities for pharmacological intervention. The emerging view of importin α is that of a key signalling molecule, with isoforms that confer preferential nuclear entry and spatiotemporal specificity on viral and cellular cargoes directly linked to human diseases

Rotational master equation for cold laser-driven molecules

The equations of motion for the molecular rotation are derived for vibrationally cold dimers that are polarized by off-resonant laser light. It is shown that, by eliminating electronic and vibrational degrees of freedom, a quantum master equation for the reduced rotational density operator can be obtained. The coherent rotational dynamics is caused by stimulated Raman transitions, whereas spontaneous Raman transitions lead to decoherence in the motion of the quantized angular momentum. As an example the molecular dynamics for the optical Kerr effect is chosen, revealing decoherence and heating of the molecular rotation.Comment: 11 pages, 5 figures, to appear in Phys. Rev.

Toxin exposure and HLA alleles determine serum antibody binding to toxic shock syndrome toxin 1 (TSST-1) of Staphylococcus aureus

Life-threatening toxic shock syndrome is often caused by the superantigen toxic shock syndrome toxin-1 (TSST-1) produced by Staphylococcus aureus. A well-known risk factor is the lack of neutralizing antibodies. To identify determinants of the anti-TSST-1 antibody response, we examined 976 participants of the German population-based epidemiological Study of Health in Pomerania (SHIP-TREND-0). We measured anti-TSST-1 antibody levels, analyzed the colonization with TSST-1-encoding S. aureus strains, and performed a genome-wide association analysis of genetic risk factors. TSST-1-specific serum IgG levels varied over a range of 4.2 logs and were elevated by a factor of 12.3 upon nasal colonization with TSST-1-encoding S. aureus. Moreover, the anti-TSST-1 antibody levels were strongly associated with HLA class II gene loci. HLA-DRB1*03:01 and HLA-DQB1*02:01 were positively, and HLA-DRB1*01:01 as well as HLA-DQB1*05:01 negatively associated with the anti-TSST-1 antibody levels. Thus, both toxin exposure and HLA alleles affect the human antibody response to TSST-1

The effect of intergalactic helium on hydrogen reionisation: implications for the sources of ionising photons at z > 6

We investigate the effect of helium on hydrogen reionisation using a hydrodynamical simulation combined with the cosmological radiative transfer code CRASH. The simulations are run in a 35.12/h comoving Mpc box using a variety of assumptions for the amplitude and power-law extreme-UV (EUV) spectral index, alpha, of the ionising emissivity. We use an empirically motivated prescription for ionising sources which ensures all of the models are consistent with constraints on the Thomson scattering optical depth and the hydrogen photo-ionisation rate at z=6. The inclusion of helium slightly delays reionisation due to the small number of ionising photons which reionise neutral helium instead of hydrogen. However, helium has a significant impact on the thermal state of the IGM. Models with alpha=3 produce IGM temperatures at the mean density at z=6 which are about 20 % higher compared to models without helium photo-heating. Harder EUV indices produce even larger IGM temperature boosts. A comparison to recent observational estimates of the IGM temperature at z=5 - 6 suggests that hydrogen reionisation was primarily driven by pop-II stellar sources with a soft EUV index, alpha<3. We also find that faint, as yet undetected galaxies, characterised by a luminosity function with a steepening faint-end slope and an increasing Lyman continuum escape fraction (fesc=0.5), are required to reproduce the ionising emissivity used in our simulations at z>6. Finally, we note there is some tension between recent observational constraints which indicate the IGM is > 10% neutral by volume z=7, and estimates of the ionising emissivity at z=6 which indicate only between 1 and 3 ionising photons are emitted per hydrogen atom over a Hubble time. This tension may be alleviated by either a lower neutral fraction at z=7 or an IGM which still remains a few % neutral by volume at z=6.Comment: 19 pages, 12 figures; MNRAS in pres

Measurement of the W±Z boson pair-production cross section in pp collisions at √s=13TeV with the ATLAS detector

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Anatomy of the sign-problem in heavy-dense QCD

QCD at finite densities of heavy quarks is investigated using the density-of-states method. The phase factor expectation value of the quark determinant is calculated to unprecedented precision as a function of the chemical potential. Results are validated using those from a reweighting approach where the latter can produce a significant signalto-noise ratio. We confirm the particle–hole symmetry at low temperatures, find a strong sign problem at intermediate values of the chemical potential, and an inverse Silver Blaze feature for chemical potentials close to the onset value: here, the phase-quenched theory underestimates the density of the full theory