One-loop quantum corrections to cosmological scalar field potentials

We study the loop corrections to potentials of complex or coupled real scalar fields used in cosmology to account for dark energy, dark matter or dark fluid. We show that the SUGRA quintessence and dark matter scalar field potentials are stable against the quantum fluctuations, and we propose solutions to the instability of the potentials of coupled quintessence and dark fluid scalar fields. We also find that a coupling to fermions is very restricted, unless this coupling has a structure which already exists in the scalar field potential or which can be compensated by higher order corrections. Finally, we study the influence of the curvature and kinetic term corrections.Comment: 11 pages, 1 figure, accepted for publication in Phys. Rev.

V,W and X in Technicolour Models

Light techni-fermions and pseudo Goldstone bosons that contribute to the electroweak radiative correction parameters V,W and X may relax the constraints on technicolour models from the experimental values of the parameters S and T. Order of magnitude estimates of the contributions to V,W and X from light techni-leptons are made when the the techni-neutrino has a small Dirac mass or a large Majorana mass. The contributions to V,W and X from pseudo Goldstone bosons are calculated in a gauged chiral Lagrangian. Estimates of V,W and X in one family technicolour models suggest that the upper bounds on S and T should be relaxed by between 0.1 and 1 depending upon the precise particle spectrum.Comment: 19 pages + 2 pages of ps figs, SWAT/1

CP Asymmetry in Charged Higgs Decays to Chargino-Neutralino

We analyze the charge-parity (CP) asymmetry in the charged Higgs boson decays to chargino-neutralino pairs, H^- -> chargino_i + neutralino_j. We show first that these modes have a large branching ratio for m_H^- > 600 GeV. We use Cutkosky rules to obtain the analytical formulas needed for the evaluation of the asymmetry under consideration. We then calculate the CP asymmetry in chargino-neutralino decays by including supersymmetric mass bounds, as well as constraints from b -> s gamma, (g-2)_mu, Delta\rho and electric dipole moments. Finally, we discuss observability of the asymmetry at the LHC by calculating the number of required charged Higgs events to observe the asymmetry for each decay channel. We show that the inclusion of constraints considerably reduces the projected CP asymmetry, and that the optimal channel for observing the asymmetry is H^- -> chargino_1 + neutralino_2.Comment: 23 pages, 8 figures, one tabl

The Kondo crossover in shot noise of a single quantum dot with orbital degeneracy

We investigate out of equilibrium transport through an orbital Kondo system realized in a single quantum dot, described by the multiorbital impurity Anderson model. Shot noise and current are calculated up to the third order in bias voltage in the particle-hole symmetric case, using the renormalized perturbation theory. The derived expressions are asymptotically exact at low energies. The resulting Fano factor of the backscattering current $F_b$ is expressed in terms of the Wilson ratio $R$ and the orbital degeneracy $N$ as $F_b =\frac{1 + 9(N-1)(R-1)^2}{1 + 5(N-1)(R-1)^2}$ at zero temperature. Then, for small Coulomb repulsions $U$, we calculate the Fano factor exactly up to terms of order $U^5$, and also carry out the numerical renormalization group calculation for intermediate $U$ in the case of two- and four-fold degeneracy ($N=2,\,4$). As $U$ increases, the charge fluctuation in the dot is suppressed, and the Fano factor varies rapidly from the noninteracting value $F_b=1$ to the value in the Kondo limit $F_b=\frac{N+8}{N+4}$, near the crossover region $U\sim \pi \Gamma$, with the energy scale of the hybridization $\Gamma$.Comment: 10 pages, 4 figure

An Effective Field Theory Look at Deep Inelastic Scattering

This talk discusses the effective field theory view of deep inelastic scattering. In such an approach, the standard factorization formula of a hard coefficient multiplied by a parton distribution function arises from matching of QCD onto an effective field theory. The DGLAP equations can then be viewed as the standard renormalization group equations that determines the cut-off dependence of the non-local operator whose forward matrix element is the parton distribution function. As an example, the non-singlet quark splitting functions is derived directly from the renormalization properties of the non-local operator itself. This approach, although discussed in the literature, does not appear to be well known to the larger high energy community. In this talk we give a pedagogical introduction to this subject.Comment: 11 pages, 1 figure, To appear in Modern Physics Letters

Lattice calculation of the lowest order hadronic contribution to the muon anomalous magnetic moment

We present a quenched lattice calculation of the lowest order (alpha^2) hadronic contribution to the anomalous magnetic moment of the muon which arises from the hadronic vacuum polarization. A general method is presented for computing entirely in Euclidean space, obviating the need for the usual dispersive treatment which relies on experimental data for e^+e^- annihilation to hadrons. While the result is not yet of comparable accuracy to those state-of-the-art calculations, systematic improvement of the quenched lattice computation to this level of accuracy is straightforward and well within the reach of present computers. Including the effects of dynamical quarks is conceptually trivial, the computer resources required are not.Comment: 12 pages, including two figures. Added reference and footnote Replaced with published version; minor changes asked for by referees and minor deletions to stay within page limi

ACD estimation of the S parameter revisited

The analytic continuation by duality (ACD) technique has been used to estimate the electroweak S parameter in technicolor models. In this letter, we investigate the reliability of this method by applying it to some toy models with known spectra. We find that in most instances the technique cannot be trusted to give a reliable result.Comment: 15 pages, LaTeX, 2 postscript figures. Uses seceqn.sty and epsfig.st

Study of the order of the phase transition in pure U(1) gauge theory with Villain action

We address the question of the order of the deconfinement phase transition of four dimensional U(1) lattice gauge theory. Simulations of the Z-gauge theory dual to the Villain action on toroidal lattices up to lattice sizes of 28^4 give results consistent with both, a vanishing and a nonvanishing discontinuity in the thermodynamic limit. A decision on the order of the phase transition requires still larger lattice sizes.Comment: LATTICE98(gauge), 3 pages, 2 figure

Anomaly Matching Conditions in Supersymmetric Gauge Theories

Sufficient conditions are proven for 't Hooft's consistency conditions to hold at points in the moduli space of supersymmetric gauge theories. Known results for anomaly matching in supersymmetric QCD are rederived as a sample application of the results. The results can be used to show that the anomaly matching conditions hold for s-confining theories.Comment: 14 pages, revte

Postmodern Technicolor

Using new insights into strongly coupled gauge theories arising from analytic calculations and lattice simulations, we explore a framework for technicolor model building that relies on a non-trivial infrared fixed point, and an essential role for QCD. Interestingly, the models lead to a simple relation between the electroweak scale and the QCD confinement scale, and to the possible existence of exotic leptoquarks with masses of several hundred GeV.Comment: LaTeX, 13 pages, version published in PR