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Stephen B. Selipsky

Publications and source records attributed to Stephen B. Selipsky.

8 recordsLinked to original sources
arXiv1997

Analyzing Chiral Symmetry Breaking in Supersymmetric Gauge Theories

We compare gap equation predictions for the spontaneous breaking of global symmetries in supersymmetric Yang-Mills theory to nonperturbative results from holomorphic effective action techniques. In the theory without matter fields, both approaches describe the formation of a gluino condensate. With $N_f$ flavors of quark and squark fields, and with $N_f$ below a certain critical value, the coupled gap equations have a solution for quark and gluino condensate formation, corresponding to breaking of global symmetries and of supersymmetry. This appears to disagree with the newer nonperturbative techniques, but the reliability of gap equations in this context and whether the solution represents the ground state remain unclear.

hep-th↗
arXiv1997

Chiral symmetry breaking, the superspace gap equation and the no-renormalization theorem

Solutions of the superspace Schwinger-Dyson equations, describing mass generation and chiral symmetry breaking in supersymmetric gauge theory, need not be constrained to vanish by no-renormalization theorems, nor by special choices of gauge parameter. Thus symmetry breaking vacuum structures remain possible (as in non-supersymmetric gauge theory), inviting comparison with predictions of an alternative approach based on holomorphy and the Wilsonian effective action.

hep-th↗
arXiv1997

Instantons and the Chiral Phase Transition

We examine the role of instantons in the zero-temperature chiral phase transition in an SU(N) gauge theory. For a range of N_f (the number of fermion flavors) depending on N, the theory exhibits an infrared fixed point at coupling $α_*$. As N_f decreases, $α_*$ increases, and it eventually exceeds a critical value sufficient to trigger chiral symmetry breaking. For the case N = 2, we estimate the critical values of N_f and $α_*$ due to instantons by numerically solving a gap equation with an instanton-generated kernel. We find instanton effects of strength comparable to that of gluon exchange.

hep-ph↗
arXiv1996

Phenomenology of the Top Mass in Realistic Extended Technicolor Models

Extended technicolor (ETC) theories typically require ETC gauge bosons lighter than of order 1 TeV, to perturbatively generate the $t$ quark mass. We point out that explicit models of $t-b$ mass splitting also typically contain additional TeV scale ETC gauge bosons transforming in the {\it adjoint} of technicolor, leading to large weak-isospin-breaking effects observable in the $ρ$ parameter. Viable ETC models may thus require a lowest ETC scale of order 10 TeV, with relatively strong and finely tuned couplings to generate $m_t$. Such models do not generate observable corrections to the $Zb{\bar b}$ vertex.

hep-ph↗
arXiv1995

Exact Results And Soft Breaking Masses In Supersymmetric Gauge Theory

We give an explicit formalism connecting softly broken supersymmetric gauge theories (with QCD as one limit) to $N=2$ and $N=1$ supersymmetric theories possessing exact solutions, using spurion fields to embed these models in an enlarged $N=1$ model. The functional forms of effective Lagrangian terms resulting from soft supersymmetry breaking are constrained by the symmetries of the enlarged model, although not well enough to fully determine the vacuum structure of generic softly broken models. Nevertheless by perturbing the exact $N=1$ model results with sufficiently small soft breaking masses, we show that there exist nonsupersymmetric models that exhibit monopole condensation and confinement in the same modes as the $N=1$ case.

hep-th↗
arXiv1993

Static Properties of Quark Solitons

It has been conjectured that at distances smaller than the confinement scale but large enough to allow for nonperturbative effects, QCD is described by an effective $SU(N_c {\times} N_f)_L\times SU(N_c {\times} N_f)_R$ chiral Lagrangian. The soliton solutions of such a Lagrangian are extended objects with spin ${1\over 2}$. For $N_c{=}3$, $N_f{=}3$ they are triplets of color and flavor and have baryon number ${1\over3}$, to be identified as constituent quarks. We investigate in detail the static properties of such constituent-quark solitons for the simplest case $N_f{=}1, N_c{=}3$. The mass of these objects comes from the energy of the static soliton and from quantum effects, described semiclassically by rotation of collective coordinates around the classical solution. The quantum corrections tend to be large, but can be controlled by exploring the Lagrangian's parameter space so as to maximize the inertia tensor. We comment on the acceptable parameter space and discuss the model's further predictive power.

hep-ph↗