Quasi-confinement in theSU(3)-gluon plasma

We investigate a phenomenological equation of state for the gluon plasma, which differs from the ideal gluon gas equation of state in three aspects: (a) it is assumed that gluons withlow momentum are subject to confining interactions anddo not contribute to the energy spectrum of free gluons; (b)only gluons withhigh momentum are considered as an ideal gas with perturbative corrections of orderO(α_s); (c) a non-perturbative vacuum pressure is included. We show that feature (a) allows for a reasonable perturbative treatment of the interaction between gluons with high momentum. The equation of state reproduces lattice data for the thermodynamical functions of theSU(3) pure gauge theory above the deconfinement transition temperatureT _c. This result suggests that a possible way to describe the gluon plasma is in terms of perturbatively interacting gluons and non-perturbative “glueball” states.     

Hydrogen-like atom in a superstrong magnetic field: Photon emission and relativistic energy level shift

Following our previous work, additional arguments are presented that in superstrong magnetic fields B ? (Zα)² B ₀, B ₀ = m ² c ³/e? ≈ 4.41 × 10¹³ G, the Dirac equation and the Schrödinger equation for an electron in the nucleus field following from it become spatially one-dimensional with the only z coordinate along the magnetic field, “Dirac” spinors become two-component, while the 2 × 2 matrices operate in the {0; 3} subspace. Based on the obtained solution of the Dirac equation and the known solution of the “onedimensional” Schrödinger equation by ordinary QED methods extrapolated to the {0; 3} subspace, the probability of photon emission by a “one-dimensional” hydrogen-like atom is calculated, which, for example, for the Lyman-alpha line differs almost twice from the probability in the “three-dimensional” case. Similarly, despite the coincidence of nonrelativistic energy levels, the calculated relativistic corrections of the order of (Zα)⁴ substantially differ from corrections in the absence of a magnetic field. A conclusion is made that, by analyzing the hydrogen emission spectrum and emission spectra at all, we can judge in principle about the presence or absence of superstrong magnetic fields in the vicinity of magnetars (neutron stars and probably brown dwarfs). Possible prospects of applying the proposed method for calculations of multielectron atoms are pointed out and the possibility of a more reliable determination of the presence of superstrong magnetic fields in magnetars by this method is considered.     

On the Energy of a “One-Dimensional” Two-Electron Atom

Based on the perturbation theory and variational method long known for a “three-dimensional” atom, the ground and first excited state energies are calculated for a “one-dimensional” two-electron atom in the “one-dimensional ortho-helium” configuration, which can be obtained experimentally in principle, as has been already done for a Na Bose condensate, or produced in a super strong magnetic field B ? (2α)²B₀ (B₀ = m²c³/e? ≈ 4.41 × 10¹³ G). The “screening constant” σ for this atom in the ground and excited states was about 0.20 and 0.17, 0.18, respectively, depending on the relative parity PP' of the electronic states, which is somewhat smaller than in “two-dimensional” and “three-dimensional” variants (in these cases, this constant in the ground state is almost the same and about 0.3). The frequencies of the main spectral lines of a “onedimensional” He atom representing a doublet split over the relative parity PP' are found. The presence of the close lines of this doublet in the emission spectrum of magnetars at frequencies ω_{1, 2} ≈ {1.15; 1.17}α²(c/λC) (α = e²/?c, λ_C =?/mc) corresponding to the “one-dimensional ortho-helium” would suggest the existence of a superstrong magnetic field in such astrophysical objects.     

Fermion-pairing on a square lattice in extreme magnetic fields

We consider the Cooper-problem on a two-dimensional, square lattice with a uniform, perpendicular magnetic field. Only rational flux fractions are considered. An extended (real-space) Hubbard model including nearest and next nearest neighbor interactions is transformed to “k-space”, or more precisely, to the space of eigenfunctions of Harper’s equation, which constitute basis functions of the magnetic translation group for the lattice. A BCS-like truncation of the interaction term is performed. Expanding the interactions in the basis functions of the irreducible representations of the point group C_4ν of the square lattice simplify calculations. The numerical results indicate enhanced binding compared to zero magnetic field, and thus re-entrant superconducting pairing at extreme magnetic fields, well beyond the point where the usual semi-classical treatment of the magnetic field breaks down.     

High-resolution photoemission study of adatom bonding effects: Cl (√2 × √2) R 45° on Cu (100)

We have investigated photoemission from an ordered $\text{(}\text{2}\text{×}\text{2}\text{) R 45°}$ Cl-overlayer on Cu (100) at good angular (Δθ ? 1°) and energy (ΔE = 100 meV) resolution. We observe two prominent adsorbate- induced features at 1.95 eV (FWHM ≈ 100 meV) and 5.4 eV (0.65 eV) below E_F. By determination of their angular momentum character, their spatial orientation and their energy dispersion, they are identified as “antibonding” and “bonding” resonances, respectively. Significant modification of the Cu d-band emission is observed and interpreted in terms of substrate orbitals which are involved in bonding.     

Universality in the partially anisotropic three-dimensional Ising lattice

Using transfer-matrix extended phenomenological renormalization-group methods, we study the critical properties of the spin-1/2 Ising model on a simple-cubic lattice with partly anisotropic coupling strengths \(\mathop J\limits^ \to = (J',J',J)\). The universality of both fundamental critical exponents y _t and y _h is confirmed. It is shown that the critical finite-size scaling amplitude ratios \(U = A_{\chi ^{(4)} } A_\kappa /A_\chi ^2 ,Y_1 = A_{\kappa ''} /A_\chi\), and \(Y_2 = A_{\kappa ^{(4)} } /A_{\chi ^{(4)} }\) are independent of the lattice anisotropy parameter Δ=J′/J. For the Y² invariant of the three-dimensional Ising universality class, we give the first quantitative estimate Y²≈2.013 (shape L×L×∞, periodic boundary conditions in both transverse directions).     

Kinetic equations within the formalism of non-equilibrium thermo field dynamics

After reviewing the real-time formalism of dissipative quantum field theory, i.e. non-equilibrium thermo field dynamics (NETFD), a kinetic equation, a self-consistent equation for the dissipation coefficient and a “mass” or “chemical potential” renormalization equation for non-equilibrium transient situations are extracted out of the two-point Green's function of the Heisenberg field, in their most general forms upon the basic requirements of NETFD. The formulation is applied to the electron-phonon system, as an example, where the gradient expansion and the quasi-particle approximation are performed. The formalism of NETFD is reinvestigated in connection with the kinetic equations.     

A criticism of the standard treatment of phonon drag

By the study of a simple example, namely the evolution in timet of an electron-phonon system with fixed, total momentum, it is shown that the “standard” treatment of “phonon drag”, which involves solving the (linearized and spatially homogeneous) coupled electron and phonon Boltzmann equations by an iteration procedure, is not always correct. In the asymptotic limit (t→∞), the iteration or “standard” procedure does not give the “correct” (i.e. the equilibrium statistical mechanical) result for the distribution of momentum between electrons and phonons. However, a proper treatment of the Boltzmann equations does lead to the “correct” sharing of momentum between electrons and phonons fort→∞. All the calculations in this paper are performed for metals at high temperatures (i.e.,T>Θ_D, the Debye temperature).     

Emergent nesting of the Fermi surface from local-moment description of iron-pnictide high-T<Subscript>c</Subscript> superconductors

We uncover the low-energy spectrum of a t-J model for electrons on a square lattice of spin-1 iron atoms with 3d _xz and 3d _yz orbital character by applying Schwinger-boson-slave-fermion mean-field theory and by exact diagonalization of one hole roaming over a 4 × 4 × 2 lattice. Hopping matrix elements are set to produce hole bands centered at zero two-dimensional (2D) momentum in the free-electron limit. Holes can propagate coherently in the t-J model below a threshold Hund coupling when long-range antiferromagnetic order across the d + = 3d _{(x + iy)z} and d ? = 3d _{(x ? iy)z} orbitals is established by magnetic frustration that is off-diagonal in the orbital indices. This leads to two hole-pocket Fermi surfaces centered at zero 2D momentum. Proximity to a commensurate spin-density wave (cSDW) that exists above the threshold Hund coupling results in emergent Fermi surface pockets about cSDW momenta at a quantum critical point (QCP). This motivates the introduction of a new Gutzwiller wavefunction for a cSDW metal state. Study of the spin-fluctuation spectrum at cSDW momenta indicates that the dispersion of the nested band of one-particle states that emerges is electron-type. Increasing Hund coupling past the QCP can push the hole-pocket Fermi surfaces centered at zero 2D momentum below the Fermi energy level, in agreement with recent determinations of the electronic structure of mono-layer iron-selenide superconductors.     

The density of states method and the velocity of sound in hot QCD

We present an initial study of the thermodynamics of hot lattice QCD using the “density of states” method, which we describe in detail. The raw data were generated from a Monte Carlo simulation of pureSU(3) gauge theory on 8³×N _t lattices, withN _t =2,4,8, at several values of the gauge coupling β. These data, taken at up to eight values of β, are then used to reconstruct the “density of states” as a function of the action and one additional observable. When combined with the proper Boltzmann weight this yieldscurves of quantities of interest as functions of the coupling constant β. These curves then yield the equation of state in a range of temperature, and the corresponding velocity of sound is obtained through appropriate derivatives. We also discuss in detail the errors, limitations, and advantages of the density of states method in its general application to QCD.     

Estimates of critical lengths and critical temperatures for classical and quantum lattice systems

Local Ward identities are derived which lead to the mean-field upper bound for the critical temperature for certain multicomponent classical lattice systems (improving by a factor of two an estimate of Brascamp-Lieb). We develop a method for accurately estimating lattice Green's functionsI _d yielding 0.3069<I ₄<0.3111 and the global bounds (d?1/2)^?<I _d <(d?1)^? for alld?4. The estimate forI _d implies the existence of a critical length for classical lattice systems with fixed length spins. Forv-component spins with fixed lengthb on the lattice ? ^d ,v=1, 2, 3, 4, the critical temperature for spontaneous magnetization satisfies $$\frac{{2Jb^2 }}{k}\frac{{d - 1}}{v}< T{}_c \leqslant \frac{{2Jb^2 }}{k}\frac{d}{v} for d \geqslant 4$$ ford4 Using GHS or generalized Griffiths' inequalities, we find that the upper bounds on the critical temperature extend to certain classical and quantum systems with unbounded spins. Absence of symmetry breakdown at high temperature for quantum lattice fields follows from bounding the energy density by a multiple ofkT. Path space techniques for finite degrees of freedom show that the high-temperature limit is classical.     

MHD effects on the channel flow of a fractional viscous fluid through a porous medium: An application of the Caputo-Fabrizio time-fractional derivative

This research article considers the exact solutions and theoretical aspects of the channel flow of a fractional viscous fluid which is electrically conducting and flowing through a porous medium. Joint Laplace and Fourier transform techniques are used to solve the momentum equation. The Caputo-Fabrizio time fractional derivative is used in the constitutive equations. Exact solutions for an arbitrary velocity are obtained, and then in the limiting cases over a bottom plate three types of flow are considered: that is, the impulsive, accelerating and oscillating motion of the fluid. The case where the flow of the fractional fluid is unaffected by the side walls, is correspondingly taken into account. For oscillating flow the solutions are separated into steady and transient parts for both sine and cosine oscillations. Moreover these solutions are captured graphically, and the effect of the Reynolds number “Re”, fractional parameter “α”, effective permeability “K_eff” and the time “t”, on the fluid's motion are observed.     

TDPAC measurements in pure and Fe-doped In 2 O 3

We try to envision that there might be a dark-matter world and neutrinos, especially the right-handed ones, might be coupled directly with dark-matter particles in the dark-matter world. The candidate model would be the extended Standard Model based on SU _c (3) × SU _L (2) × U(1) × SU _f (3) × SU _R (2), with the search of the detailed version through the aid of the two working rules, “Dirac similarity principle” and “minimum Higgs hypothesis”.     

Phenomenology ofSO(10) unified superstring models with intermediate scaleSU R(2) breaking

Electroweak breaking and the supersymmetric particle spectrum are discussed in superstring theories where the gauge group after compactification isSO(10)×E _s ^′ , and where the gauge symmetry after flux breaking isSU(3)×SU(2)×SU(2)×U(1).     

Self-consistent approximations for correlation functions in the theory of triplet pairing superfluidity in3He

A self-consistent and “spin conserving” approximation scheme is developed for the two-particle correlation functions in superfluid³He. It is shown that the irreducible vertex part occuring in the Bethe-Salpeter equation for the generalized correlation function (having 4⁴ components) must be equal to the functional derivative of the approximate self-energy part with respect to the Green's function. The theory is specialized to the Hartree-Fock approximation yielding the RPA susceptibility belowT _c . An important feature of the resulting diagrammatic expansion is that the spin-fluctuation effects in the superfluid phase arise from infinite iteration of pairs of anomalous propagators inboth the particle-hole and in the particle-particle channels.     

Phase Coexistence in Nanoscopically Thin Films Confined by Asymmetric Walls

Thin Ising films with nearest-neighbor ferromagnetic exchange in a bulk magnetic field H are studied in a L×L×D geometry, where at the opposite walls, given by the L×L surfaces, local magnetic fields H ₁, and H _D act. While in previous work, the symmetric case H ₁=H _D (leading to “capillary condensation”, when one applies the lattice gas terminology) as well as the antisymmetric case H ₁=?H _D (leading to “interface localization transitions”) were studied, we focus here on the general ‘asymmetric’ case. Monte Carlo simulations are carried out and analyses based on thermodynamic integration methods are used to establish the phase diagrams and study the properties of the coexisting phases. A discussion is given why for the range of thicknesses that is explored (16≤D≤80 lattice spacings) this is the most suitable methodology. Restricting attention to cases where in the semi-infinite system a first-order wetting transition occurs, it is shown that the latter, due to confinement, is turned in a thin-film triple point. Above the triple point, narrow two-phase coexistence curves are found, which are the analog of prewetting transitions in the semi-infinite system. A comparison to related results for (symmetrical) polymer blends and (asymmetric) colloid-polymer mixtures is made.     

Coherent Exchange Cluster Approach for two-dimensional disordered Heisenberg-spin system

The Coherent Exchange Cluster Approach, developed within two proceeding papers, is applied to dilute quasi two-dimensional Heisenberg spin-systems, consisting of one magnetic and one nonmagnetic alloying component. The level density of spin wave excitations is discussed for concentrations of the magnetic component, which are larger than the critical value, where all excitations become localized. The propagation of the excitations through the disordered system is described by an effective Heisenberg-Hamiltonian with a complex and energy-dependent exchange integral \(\tilde J\) (E). This quantity is determined by the postulate, that the most important matrix elements of the scatteringT-matrix should vanish after averaging over the possible configurations of a scattering cluster, consisting of a central lattice site and its four nearest neighbours. Numerical results are obtained both for the “dilute bond” and “site” problems, respectively; in both cases, the results agree rather well with existing computer simulations for 30 × 30 spin arrays. For the “site” problem, it is necessary to introduce a coherent single ion anisotropy field in addition to the coherent exchange integral: Results in agreement with the analyticity requirements are obtained by a careful choice of the additional selfconsistency equation.     

Estimation of changes in parameters of a crystal lattice and energy bands upon variation in the size of nanocrystals and nanofilms of silicides prepared by ion implantation

Changes in the parameters of the crystal lattice and energy bands of CoSi₂ nanofilms and nanocrystals formed in the surface Si layers by ion implantation combined with annealing are studied. It is shown that the band gap E _g of CoSi₂/Si(100) nanofilms with the thickness θ ≤ 40–50 Å is higher by ～0.1 eV than for “thick” films; in the case of nanocrystals, E _g is 0.3–0.4 eV higher than for macrocrystals.