arXiv subjects

Stephen D. H. Hsu

Publications and source records attributed to Stephen D. H. Hsu.

111 records · Page 7Linked to original sources

arXiv1992

A New Anomaly Matching Condition?

We formulate ``Witten'' matching conditions for confining gauge theories. The conditions are analogous to 't Hooft's, but involve Witten's global SU(2) anomaly. Using a group theoretic result of Geng, Marshak, Zhao and Okubo, we show that if the fourth homotopy group of the flavor group $H$ is trivial ($Π_4(H) = 0$) then realizations of massless composite fermions that satisfy the 't Hooft conditions also satisfy the Witten conditions. If $Π_4 (H)$ is nontrivial, the new matching conditions can yield additional information about the low energy spectrum of the theory. We give a simple physical proof of Geng, et. al.'s result.

hep-ph↗

arXiv1992

Walking Technicolor and Electroweak Radiative Corrections

We examine the effect of walking technicolor dynamics on the electroweak $S$ parameter and contrast it with the effect of QCD-like technicolor dynamics. Our main tools are the operator product expansion for the high-momentum behavior of the electroweak gauge boson vacuum polarizations and the analyticity of these polarizations which relate their low and high momentum behaviors. We show that whereas in large QCD-like technicolor models $S$ is large and positive, in walking technicolor models a negative contribution is emphasized, related to the large anomalous dimension of the technifermion condensate. Thus in walking technicolor $S$ is determined by a large cancellation of two competing effects. This may result in much smaller values of $S$ than in QCD-like technicolor, although considerable uncertainties are involved. We conclude that it is impossible to rule out walking technicolor based on the present experimental limits on $S$ and the present theoretical technology.

hep-ph↗

arXiv1992

On tunneling at finite energies and temperatures

We study the contribution of finite energy tunneling to the total vacuum transition rate in a system at finite temperature. We find that in certain models, such as the 1+1 Abelian Higgs model, the quantum contribution is non-negligible even at large temperatures. We show how the persistence of the cosmological baryon asymmetry yields a bound on the inclusive two particle cross section in the anomalous (B violating) sector.

hep-ph↗