Hyperfine splittings and gf values of metastable h2
Coupling constants of hyperfine structure evaluated by using single configuration electronic wave function for metastable molecular hydrogen
METASTABLE ATOM↗
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Results for “COUPLING CONSTANTS”
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Characteristics of Superconducting State in Vanadium: the Eliashberg Equations and Semi-analytical Formulas
The superconducting state in vanadium characterizes with the critical temperature (T{sub c}) equal to 5.3 K. The Coulomb pseudopotential, calculated with the help of the Eliashberg equations, possesses anomalously high value μ{sup ⋆}(3Ω{sub max}) = 0.259 or μ{sup ⋆}(10Ω{sub max}) = 0.368 (Ω{sub max} denotes the maximum phonon frequency). Despite the relatively large electron-phonon coupling constant (λ = 0.91), the quantities such as the order parameter (Δ), the specific heat (C), and the thermodynamic critical field (H{sub c}) determine the values of the dimensionless ratios not deviating much from the predictions of the BCS theory: R{sub Δ} = 2Δ(0)/k{sub B}T{sub c} = 3.68, R{sub C} = ΔC(T{sub c}) /C{sup N}(T{sub c}) = 1.69, and R{sub H}=T{sub c}C{sup N}(T{sub c})/H{sub c}{sup 2}(0)=0.171. This result is associated with the reduction of the strong-coupling and the retardation effects by the high value of the Coulomb pseudopotential. It has been shown that the results of the Eliashberg formalism can be relatively precisely reproduced with the help of the semi-analytical formulas, if the value of μ{sup ⋆} is determined on the basis of the T{sub c}-Allen-Dynes expression (μAD⋆ = 0.198). The attention should be paid to the fact that in the numerical and in the semi-analytical approach the comparable values of the thermodynamic parameters for the same μ{sup ⋆} have been obtained only in the vicinity of the point μ{sup ⋆} = 0.1.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Spin-Wave Resonance in Chemically Deposited Fe-Ni Films: Measuring the Spin-Wave Stiffness and Surface Anisotropy Constant
Single-layer Fe{sub x}Ni{sub 1-x} thin magnetic films have been investigated by the spin-wave resonance technique in the entire concentration range. The surface anisotropy and exchange stiffness constants for the films with a Ni content from 30 to 80 at % have been measured from the experimental standing spin wave spectra. The surface exchange spin wave penetration depth δ{sub C} = 20–30 nm has been determined from the dependences of the surface anisotropy and exchange coupling constants on the Fe{sub 20}Ni{sub 80} film thickness in the range of 250–400 nm.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Iron and manganese-related magnetic centers in hexagonal silicon carbide: A possible roadmap for spintronic devices
The electronic and magnetic properties of manganese- and iron-doped 4H-SiC were investigated by first-principles calculations, using an all electron methodology. The results on stability, spin configurations, formation and transition energies, local magnetic moments, and hyperfine parameters were compared to available theoretical and experimental data. The results indicated that transition metal impurities are energetically more favorable in lattice sites with carbon atoms as their first nearest neighbors, in both substitutional and interstitial configurations, which results from the larger electronegativity of carbon with respect to that of silicon. The analysis of the electronic properties of those impurity centers showed that they could stay in several stable charge states, depending on the Fermi energy level position within the host SiC bandgap. Additionally, by computing the p-d exchange coupling constant, which is related to a spin polarization in the SiC valence band top, we explored the possibility of achieving macroscopic magnetism in SiC. The results indicated that some centers, in both substitutional and interstitial configurations, present reasonably strong magnetic couplings to mediate macroscopic magnetism at high temperatures, which may generate spin polarized currents, leading to applications in spintronic devices.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
The problem with false vacuum Higgs inflation
We investigate the possibility of using the only known fundamental scalar, the Higgs, as an inflaton with minimal coupling to gravity. The peculiar appearance of a plateau or a false vacuum in the renormalised effective scalar potential suggests that the Higgs might drive inflation. For the case of a false vacuum we use an additional singlet scalar field, motivated by the strong CP problem, and its coupling to the Higgs to lift the barrier allowing for a graceful exit from inflation by mimicking hybrid inflation. We find that this scenario is incompatible with current measurements of the Higgs mass and the QCD coupling constant and conclude that the Higgs can only be the inflaton in more complicated scenarios.
79 ASTRONOMY AND ASTROPHYSICS↗
Null lifts and projective dynamics
We describe natural Hamiltonian systems using projective geometry. The null lift procedure endows the tangent bundle with a projective structure where the null Hamiltonian is identified with a projective conic and induces a Weyl geometry. Projective transformations generate a set of known and new dualities between Hamiltonian systems, as for example the phenomenon of coupling-constant metamorphosis. We conclude outlining how this construction can be extended to the quantum case for Eisenhart–Duval lifts.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Analytic first derivatives for a spin-adapted open-shell coupled cluster theory: Evaluation of first-order electrical properties
An analytic scheme is presented for the evaluation of first derivatives of the energy for a unitary group based spin-adapted coupled cluster (CC) theory, namely, the combinatoric open-shell CC (COSCC) approach within the singles and doubles approximation. The widely used Lagrange multiplier approach is employed for the derivation of an analytical expression for the first derivative of the energy, which in combination with the well-established density-matrix formulation, is used for the computation of first-order electrical properties. Derivations of the spin-adapted lambda equations for determining the Lagrange multipliers and the expressions for the spin-free effective density matrices for the COSCC approach are presented. Orbital-relaxation effects due to the electric-field perturbation are treated via the Z-vector technique. We present calculations of the dipole moments for a number of doublet radicals in their ground states using restricted open-shell Hartree-Fock (ROHF) and quasi-restricted HF (QRHF) orbitals in order to demonstrate the applicability of our analytic scheme for computing energy derivatives. We also report calculations of the chlorine electric-field gradients and nuclear quadrupole-coupling constants for the CCl, CH{sub 2}Cl, ClO{sub 2}, and SiCl radicals.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Analysis of the theoretical bias in dark matter direct detection
Fitting the model ''A'' to dark matter direct detection data, when the model that underlies the data is ''B'', introduces a theoretical bias in the fit. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the effective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matter-nucleon interaction, and an anisotropic dark matter velocity distribution. Then, we fit a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best fit values of the dark matter particle mass differ from their benchmark values up to 2 standard deviations. The best fit values of the dark matter-nucleon coupling constant differ from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially significant bias.
79 ASTRONOMY AND ASTROPHYSICS↗
Comparison of LHC and ILC Capabilities for Higgs Boson Coupling Measurements
I estimate the accuracies on Higgs boson coupling constants that experiments at the Large Hadron Collider and the International Linear Collider are capable of reaching over the long term.
43 PARTICLE ACCELERATORS↗
Bose gases near resonance: Renormalized interactions in a condensate
Bose gases at large scattering lengths or beyond the usual dilute limit for a long time have been one of the most challenging problems in many-body physics. In this article, we investigate the fundamental properties of a near-resonance Bose gas and illustrate that three-dimensional Bose gases become nearly fermionized near resonance when the chemical potential as a function of scattering lengths reaches a maximum and the atomic condensates lose metastability. The instability and accompanying maximum are shown to be a precursor of the sign change of g{sub 2}, the renormalized two-body interaction between condensed atoms. g{sub 2} changes from effectively repulsive to attractive when approaching resonance from the molecular side, even though the scattering length is still positive. This occurs when dimers, under the influence of condensates, emerge at zero energy in the atomic gases at a finite positive scattering length. We carry out our studies of Bose gases via applying a self-consistent renormalization group equation which is further subject to a boundary condition. We also comment on the relation between the approach here and the diagrammatic calculation in an early article [D. Borzov, M.S. Mashayekhi, S. Zhang, J.-L. Song, F. Zhou, Phys. Rev. A 85 (2012) 023620]. - Highlights: Black-Right-Pointing-Pointer A Bose gas becomes nearly fermionized when its chemical potential approaches a maximum near resonance. Black-Right-Pointing-Pointer At the maximum, an onset instability sets in at a positive scattering length. Black-Right-Pointing-Pointer Condensates strongly influence the renormalization flow of few-body running coupling constants. Black-Right-Pointing-Pointer The effective two-body interaction constant changes its sign at a positive scattering length.
74 ATOMIC AND MOLECULAR PHYSICS↗
Two-loop free energy of three-dimensional antiferromagnets in external magnetic and staggered fields
Using a model-independent low-energy effective field theory, we calculate the free energy of three-dimensional antiferromagnets in a combination of mutually perpendicular external magnetic and staggered fields at the next-to-next-to-leading, two-loop order. Renormalization is carried out analytically, and the renormalization group invariance of the result is checked explicitly. The free energy is thus expressed solely in terms of temperature, the external fields, and a set of low-energy coupling constants, to be determined by experiment or by matching to the microscopic model of a given concrete material.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
On a simple way to calculate electronic resonances for polyatomic molecules
We propose a simple method for calculation of low-lying shape electronic resonances of polyatomic molecules. The method introduces a perturbation potential and requires only routine bound-state type calculations in the real domain of energies. Such a calculation is accessible by most of the free or commercial quantum chemistry software. The presented method is based on the analytical continuation in a coupling constant model, but unlike its previous variants, we experience a very stable and robust behavior for higher-order extrapolation functions. Moreover, the present approach is independent of the correlation treatment used in quantum many-electron computations and therefore we are able to apply Coupled Clusters (CCSD-T) level of the correlation model. We demonstrate these properties on determination of the resonance position and width of the {sup 2}Π{sub u} temporary negative ion state of diacetylene using CCSD-T level of theory.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
GravitoMagnetic Field in Tensor-Vector-Scalar Theory
We study the gravitomagnetism in the TeVeS theory. We compute the gravitomagnetic field that a slow moving mass distribution produces in its Newtonian regime. We report that the consistency between the TeVeS gravitomagnetic field and that predicted by the Einstein-Hilbert theory leads to a relation between the vector and scalar coupling constants of the theory. We translate the Lunar Laser Ranging measurement's data into a constraint on the deviation from this relation.
79 ASTRONOMY AND ASTROPHYSICS↗
Thermodynamic phase transition in the rainbow Schwarzschild black hole
We study the thermodynamic phase transition in the rainbow Schwarzschild black hole where the metric depends on the energy of the test particle. Identifying the black hole temperature with the energy from the modified dispersion relation, we obtain the modified entropy and thermodynamic energy along with the modified local temperature in the cavity to provide well defined black hole states. It is found that apart from the conventional critical temperature related to Hawking-Page phase transition there appears an additional critical temperature which is of relevance to the existence of a locally stable tiny black hole; however, the off-shell free energy tells us that this black hole should eventually tunnel into the stable large black hole. Finally, we discuss the reason why the temperature near the horizon is finite in the rainbow black hole by employing the running gravitational coupling constant, whereas it is divergent near the horizon in the ordinary Schwarzschild black hole.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Chiral condensate beyond the one-loop approximation
A two-dimensional model involving a fermion field and a self-interacting scalar field with Yukawa interaction is studied beyond the one-loop approximation. It is shown that, in this model, the chiral condensate vanishes at two values of the Yukawa coupling constant. In one case, the respective symmetry is restored, while, in the other case, it is not restored.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Extended BCS-Bose Crossover
Applying the generalized Bose-Einstein condensation (GBEC) formalism, we extend the BCS-Bose crossover theory by explicitly including hole Cooper pairs (2hCPs). From this, follows a phase diagram with two pure phases, one with 2hCPs and the other with electron Cooper pairs (2eCPs), plus a mixed phase with arbitrary proportions of 2eCPs and 2hCPs. The special-case phase when there is perfect symmetry, i.e., with ideal 50-50 proportions between 2eCPs and 2hCPs, corresponds to the usual BCS-Bose crossover. Explicitly including 2hCPs yields an extended BCS-Bose crossover which predicts improved T{sub c}/T{sub F} values for some conventional superconductors (i.e., with electron-phonon dynamics) when compared with experiment. To do this, we employ the BCS dimensionless coupling constant λ{sub BCS} via the BCS gap equation and compare with the Bogoliubov et al. upper limit λ{sub BCS} ≤ 1/2. Another phase diagram presented exhibits experimental T{sub c}/T{sub F} values for some conventional superconductors for arbitrary proportions between 2eCPs and 2hCPs as function of Δn = n/n{sub f} − 1, where n is the electron concentration and n{sub f} that of unbound electrons at T = 0. The extended crossover is compared with experimental T{sub c}/T{sub F} values as well as to the gap-to- T{sub c} ratio.
74 ATOMIC AND MOLECULAR PHYSICS↗
Some specific features of light propagation in a three-channel nonlinear directional coupler
Exact analytical solutions have been obtained to the system of nonlinear differential equations for the intensities of the waves propagating in a three-channel nonlinear directional coupler with a Kerr nonlinearity and different coupling constants between the optical waveguides. (integrated optics)
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Magnetovolume effects and effect of pressure on the temperature dependence of sublattice magnetization in Ho(Co{sub 0.9}Ga{sub 0.1}){sub 2} compounds
The temperature dependence of the magnetic moments of cobalt and holmium ions in the temperature range of 5–300 K at pressures of P = 0 and 5 kbar was determined based on neutron diffraction data on Ho(Co{sub 0.9}Ga{sub 0.1}){sub 2} intermetallide. The temperature dependence of the lattice parameter was established, and the spontaneous bulk magnetostriction was determined. These quantities were calculated using the exchange striction model of a ferrimagnet, and good agreement with the experiment was obtained. The parameters of the exchange interaction between pairs of atoms of this compound and the magnetoelastic coupling constant were estimated. An original interpretation of the nature of the first-order magnetic phase transition in HoCo{sub 2} is proposed.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗