Imaginary part in gluon self-energy

The real time finite temperature perturbation is carried out for the imaginary part of gluon self-energy in the general covariant gauge. Using the result we obtain the electric susceptibility and the magnetic permeability. We show that their imaginary part has a correct sign in the space-like momentum region and hence the finite temperature perturbation in QCD is meaningful, contrary to the assertion due to Hansson and Zahed based on the analysis in the time-like momentum region only.     

Gauge covariant linear response analysis of QCD plasma oscillations

We show, using linear response theory, how plasma oscillations and screening in quark-gluon plasma can be computed in perturbation theory in a gauge covariant manner. Using this method we calculate the damping constant of color electric plasma oscillations in a Colomb gauge and show that the result agrees with an earlier calculation in the A₀ = 0 gauge.     

Polarisation dependence of photon antibunching phenomena involving light propagation in isotropic media

By the method of “short optical paths”, the dynamics of photon antibunching is shown to depend on the polarisation state of the photons and their two-photon absorption in an isotropic medium. In the case of self-induced optical birefringence, a change in helicity of the elliptically polarized beam or a change in sign of the angle between the large semi-axis of the ellipse and the analyzer causes a reversal of antibunching into bunching. Linear and circular polarisation of the photons are discussed as well for antibunching related with two-photon absorption, defined by the imaginary part of the molecular hyperpolarizability tensor.     

Hadron potentials within the gauge/string correspondence

It is known, since the 70s, that the large N 't Hooft limit of gauge theories is related to string theories. In 1998, J. M. Maldacena identified precisely such a relation: the so-called AdS/CFT correspondence which speculates a duality between a large N strongly-coupled supersymmetric and conformal Yang-Mills theory in four dimensions and a weakly-coupled string theory defined in a five-dimensional anti-de Sitter AdS₅ space-time. This review aims at introducing concepts and methods used to derive, in the framework of the gauge/string correspondence, the interaction potentials of mesons and baryons at zero and finite temperature. The dual string configurations associated with the different kinds of hadrons are described and their behaviours at short and large distances are understood. Although the application of Maldacena's AdS/CFT conjecture to QCD is not straightforward, QCD being neither supersymmetric nor conformal, the AdS/QCD correspondence approach attempts to identify the dual theory of QCD. Especially, the study of heavy quark-antiquark bound-states leads to establish general dual criteria for the confinement.     

Band structure and optical functions of ternary chain TlInSe2

The band structure of ternary chain TlInSe₂ is calculated by a pseudo-potential method with allowance for non-locality of ionic pseudo-potentials. In the obtained band structure the symmetry and forbidden character of the direct transitions at band gap are ascertained to be the same as reported earlier from the results of the empirical pseudo-potential calculations. The imaginary part of the components parallel and perpendicular to the c-axis of the dielectric function tensor of TlInSe₂ is calculated at photon energies up to 10 eV. The real part of these components is obtained by extrapolation of the imaginary part to higher energies and subsequent Kramers–Kronig transformation. The obtained dielectric function is compared with the one obtained ellipsometrically in the range 0.85–6.5 eV. The results of comparison are rather favorable.     

Cosmological perturbations: a new gauge-invariant approach

A new gauge-invariant approach for describing cosmological perturbations is developed. It is based on a physically motivated splitting of the stress-energy tensor of the perturbation into two parts—the bare perturbation and the complementary perturbation associated with stresses in the background gravitational field induced by the introduction of the bare perturbation. The complementary perturbation of the stress-energy tensor is explicitly singled out and taken to the left side of the perturbed Einstein equations so that the bare stress-energy tensor is the sole source for the perturbation of the metric tensor and both sides of these equations are gauge invariant with respect to infinitesimal coordinate transformations. For simplicity we analyze the perturbations of the spatially-flat Friedmann–Lemaı̂tre–Robertson–Walker (FLRW) dust model. A cosmological gauge can be chosen such that the equations for the perturbations of the metric tensor are completely decoupled for the h₀₀, h_0i, and h_ij metric components and explicitly solvable in terms of retarded integrals.     

Wilson coefficients for parton decay at order αs

We calculate, at order α_s, certain Wilson coefficients that relate to the P_T spread of quark jets in QCD. Also included is a calculation of the quark decay function d(z) in a spacelike axial gauge.     

Spin asymmetries in large-pT production of gauge bosons based on quantum chromodynamics and electroweak gauge model

We make predictions for spin asymmetries in the production of gauge bosons, such as Z⁰, Wsu± and γ, at large p_T from the collision of longitudinally polarized hadrons using QCD perturbation theory and the electroweak gauge model in the framework of a hard scattering model. Asymmetries typically at the 20% and 4% level are predicted for the weak bosons and photon, respectively. Experimental tests should be possible in the near future, e.g., at Fermilab, ISABELLE and colliding SPS.     

Lattice QCD Towards Nuclear Forces

Recent studies of nuclear forces based on lattice QCD are presented. Not only the central potential but also the tensor potential is deduced from the Nambu?CBethe?CSalpeter wave function measured with lattice QCD. This method is applied to various kinds of nuclear potentials, such as ${V_{NN}, V_{\Lambda N}, V_{p{\Xi}^0},V_{\Lambda\Lambda-N\Xi-\Sigma\Sigma}}$ (coupled-channel potential), and ${V^{\{{\bf {27},{8}_s,{1},{10},\overline{10},{8}_a}\}}}$ (flavor representation potential). The energy dependence and the angular momentum dependence of the quenched V _NN is studied. A challenge for three-nucleon force from lattice QCD is also presented.     

Mass mixing,CP violation and left-right symmetry for heavy neutral mesons

We investigate \(M^0 - \bar M^0 \) mixing and CP violation in the minimal left-right symmetric gauge model with spontaneous P and CP violation. The dominant contributions to the mixing amplitude including QCD corrections are calculated explicitly for \(B^0 - \bar B^0 \) . While the amount of mixing is not much changed with respect to the standard model leftright symmetry can give rise to significantly larger CP violation in the \(B_s^0 - \bar B_s^0 \) system (up to two orders of magnitude for the dilepton charge asymmetry). Sizable CP violating effects require that the left-right contribution to theK _L K _S mass difference has the same sign as the standard model contribution. We also comment on \(D^0 - \bar D^0 \) mixing including a careful discussion of the standard model prediction for the short distance part.     

Proof of factorization of fragmentation function in non-equilibrium QCD

In this paper, we prove factorization of fragmentation function in non-equilibrium QCD by using Schwinger-Keldysh closed-time path integral formalism. We use the background field method of QCD in a pure gauge in path integral approach to prove factorization of fragmentation function in non-equilibrium QCD. Our proof is valid in any arbitrary gauge fixing parameter α. This may be relevant to study hadron production from quark-gluon plasma at high energy heavy-ion colliders at RHIC and LHC.     

A field configuration closer to the true QCD vacuum

An effective action for QCD at one-loop order, which is real, manifestly Lorentz and gauge invariant and which depends on an infinite family of gauge invariants (tr(F _μν F _μν), tr(F _μν F _μν F _?σ F _?σ),...), is obtained. Moreover, anAnsatz for a vacuum configuration is made, whose corresponding vacuum energy density is lower than the one for the SavvidyAnsatz. Both the cases of pure QCD and of QCD with massless fermions are considered.     

The Non-Perturbative Approach to the Infrared Problem in QCD at Finite Temperature

A non-perturbative approach is developed for investigation of the infrared problem in QCD at T ≠ 0 in the ghost-free axial gauge. The problem is solved by using a 3-dimensional theory within the exact Slavnov-Taylor identities and Schwinger-Dyson equations. The system of two non-linear integral equations for the structural functions of the gluon polarization tensor is obtained whose solution determines the infrared behavior of the temperature Green functions in the 4-dimensional QCD. The simplest solution of these equations which is the same as the first term of the perturbation expansion shows the presence of singularities in the gluon propagator at momenta p ∼ g²T, that cannot be eliminated by any choice of the gauge. The infrared instability of QCD at T ≠ 0 caused by these singularities is discussed.     

Towards a complete QFT treatment of monopole induced baryon number violating transitions

By showing that the radially reduced QCD of s-wave fermions outside the core of a GUT monopole can be treated in a way analogous to 't Hofft's QCD₂ in the large N_climit, we are able to give a complete QFT treatment of all the relevant long-range gauge fields outside the monopole core. We prove that the original cluster argument for the existence of baryon number violating fermion “condensates” around the core, gives in fact, the correct result, despite the neglect of QCD strong interactions, which prevent the propagation of isolated quarks. We discuss briefly how a complete computational framework for a monopole induced hadron-lepton transition might be derived.     

New D = 10, N = 1 superspace supergravity and local symmetries of superstrings

The superspace formulation of new D = 10, N = 1 supergravity is developed. It is shown that the background superspace of the new theory can be coupled to a test superstring in such a way that the local symmetries of the superstring are intact. This formulation necessarily makes use of the Vainberg construction so the action is analogous to the effective action for QCD with the WZW term. The results suggest that the ambiguity between the massless two-form and six-form in the SO(32) or E₈ × E₈ superstring theories can only be resolved by a gauge invariant, Lorentz-covariant formulation of superstring field theory.     

Properties of quark matter governed by quantum chromodynamics (II). Renormalization schemes in quark matter

Renormalization schemes are examined (in the Coulomb gauge) for quantum chromodynamics in the presence of quark matter. We demand that the effective coupling constant for all schemes become congruent with the vacuum QCD running coupling constant as the matter chemical potential, μ, goes to zero. Also, to enable us to standardize with the vacuum QCD running coupling constant at some asymptotic momentum transfer, $\text{|}\text{p}{}_0\text{|,}\text{we keep}\text{μ ? ¦}\text{p}{}_0\text{¦}$, to ensure that the matter contribution is negligible at this point. This means all schemes merge with vacuum QCD at $\text{|}\text{p}{}_0\text{|}$ and beyond. Two renormalization group invariants are shown to emerge: (i) the effective or invariant charge, g_inv², which is, however, scheme dependent and (ii) g²(M)/S(M), where S(M)^?1 is the Coulomb propagator, which is scheme independent. The only scheme in which g_inv² is scheme independent and identical to g²(M)/S(M) is the screened charged scheme (previous paper) characterised by the normalization of the entire Green function, S^?1, to unity. We conclude that this is the scheme to be used if one wants to identify with the experimental effective coupling in perturbation theory. However, if we do not restrict to perturbation theory all schemes should be allowed. Although we discuss matter QCD in the Coulomb gauge, the above considerations are quite general to gauge theories in the presence of matter.     

Higgs detection via Z0 polarisation

It is demonstrated that if one determines the polarisation of the Z⁰ final states from pp → Z⁰Z⁰ → charged leptons, then one can reliably detect the presence of a Higgs boson in the range 300 GeV < m_H < 1 TeV at the SSC. This is in contrast to other methods for Higgs detection which are susceptible to QCD backgrounds, severe cuts, or uncertainties in the Z⁰ continuum. For one year's running at the nominal SSC luminosity of 10³³ cm⁻² s⁻¹ and energy 40 TeV there are sufficient numbers of such events to perform the straightforward analysis.     

Coupled Channel Approach to S-Wave Hyperonic Interactions from Lattice QCD

We studied hyperonic interactions by lattice QCD simulation throuth coupled channel formalism. Our approach to baryon-baryon interactions is deriving a potential from inverting Schrödinger equation using Nambu-Bethe-Salpeter (NBS) wave function simulated on the lattice. The quark mass dependences and flavor SU(3) breaking effects of the potential matrix are also discussed by comparing with results of gauge configurations with different quark masses. Our numerical results are obtained from three ensembles of 2+1 flavor QCD gauge configurations, which corresponds to m _π ~ 700, 570 and 410 MeV, provided by the PACS-CS Collaboration.     

<Emphasis Type="Italic">B</Emphasis> and <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">s</Emphasis></Subscript> decay constants from moments of finite energy sum rules in QCD

We use an appropriate combination of moments of finite energy sum rules in QCD in order to compute the B _q -meson decay constants f _B and . We perform the calculation using a two-loop computation of the imaginary part of the pseudoscalar two point function in terms of the running bottom quark mass. The results are stable against the so-called QCD duality threshold, and they are in agreement with the estimates obtained from Borel transform QCD sum rules and lattice computations.Received: 28 July 2004, Revised: 10 September 2004, Published online: 23 November 2004PACS: 12.38.Bx, 12.38.LgSupported by MCYT-FEDER under contract FPA2002-00612.     

N = 1 super quantum chromo dynamics and fractional branes

In this talk we show how to get the one-loop beta function and the chiral anomaly ofN = 1 super QCD from a stack of fractionalN D3-branes localized inside the world-volume of 2M fractionalD7-branes in the orbifoldC ³/(Z ₂ ×Z ₂). They are obtained by analyzing the classical supergravity background generated by such a brane configuration, in the spirit of the gauge/gravity correspondence.