Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman
Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman
Physics Faculty Research & Creative Works
We report a first-principles density-functional calculation of the electronic structure and properties of the recently discovered superconducting β-pyrochlore oxide KOs2O6. We find that the electronic structure near the Fermi energy EF is dominated by strongly hybridized Os 5d and O 2p states. A van Hove singularity very close to Ef leads to a relatively large density of states at EF, and the Fermi surface exhibits strong nesting along several directions. These features could provide the scattering processes leading to the observed anomalous temperature dependence of the resistivity and to the rather large …
Instantons In Quantum Mechanics And Resurgent Expansions, Ulrich D. Jentschura, Jean Zinn-Justin
Instantons In Quantum Mechanics And Resurgent Expansions, Ulrich D. Jentschura, Jean Zinn-Justin
Physics Faculty Research & Creative Works
Certain quantum mechanical potentials give rise to a vanishing perturbation series for at least one energy level (which as we here assume is the ground state), but the true ground-state energy is positive. We show here that in a typical case, the eigenvalue may be expressed in terms of a generalized perturbative expansion (resurgent expansion). Modified Bohr-Sommerfeld quantization conditions lead to generalized perturbative expansions which may be expressed in terms of nonanalytic factors of the form exp(-a/g), where a>0 is the instanton action, and power series in the coupling g, as well as logarithmic factors. The ground-state energy, for …
Order-Parameter Symmetry And Mode-Coupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan
Order-Parameter Symmetry And Mode-Coupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan
Physics Faculty Research & Creative Works
We derive an order-parameter field theory for a quantum phase transition between a disordered metal and an exotic (non- s -wave) superconductor. Mode coupling effects between the order parameter and other fermionic soft modes lead to an effective long-range interaction between the anomalous density fluctuations which is reflected in singularities in the free energy functional. However, this long-range interaction is not strong enough to suppress disorder fluctuations. The asymptotic critical region is characterized by run-away flow to large disorder. For weak coupling, this asymptotic region is very narrow. It is preempted by a wide crossover regime with mean-field critical behavior …
Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia
Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia
Physics Faculty Research & Creative Works
If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on …
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Physics Faculty Research & Creative Works
In models with large extra dimensions, particle collisions with a center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 108 TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large …
Extrapolation Of The Zα-Expansion And Two-Loop Bound-State Energy Shifts, Ulrich D. Jentschura
Extrapolation Of The Zα-Expansion And Two-Loop Bound-State Energy Shifts, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
Quantum electrodynamic (QED) effects that shift the binding energies of hydrogenic energy levels have been expressed in terms of a semi-analytic expansion in powers of Zα and ln[(Zα)-2], where Z is the nuclear charge number and α is the fine-structure constant. For many QED effects, numerical data are available in the domain of high Z where the Zα expansion fails. In this Letter, we demonstrate that it is possible, within certain limits of accuracy, to extrapolate the Zα-expansion from the low-Z to the high-Z domain. We also review two-loop self-energy effects and provide an estimate for the problematic …
Mechanism For Carrier Velocity Saturation In Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Mechanism For Carrier Velocity Saturation In Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Physics Faculty Research & Creative Works
We present a possible mechanism for the saturation of the velocity of photoinjected charge carriers in pure organic crystals, the analysis having been motivated by observations in pentacene. The mechanism is based on the strong wave vector dependence of the damping coefficient appearing in the appropriate effective mass equation. Our primary goal is to explore this mechanism in general terms rather than to apply it to a specific system such as pentacene. Our analysis is based on a Fokker-Planck equation treatment. We indicate how the damping coeffcient is related to relaxation times in usual Boltzmann equations and how it can …