1,326 research outputs found
Nonperturbative Matching for Field Theories with Heavy Fermions
We examine a paradox, suggested by Banks and Dabholkar, concerning
nonperturbative effects in an effective field theory which is obtained by
integrating out a generation of heavy fermions, where the heavy fermion masses
arise from Yukawa couplings. They argue that light fermions in the effective
theory appear to decay via instanton processes, whereas their decay is
forbidden in the full theory. We resolve this paradox by showing that such
processes in fact do not occur in the effective theory, due to matching
corrections which cause the relevant light field configurations to have
infinite action.Comment: 10 pages, no figures, uses harvmac, Harvard University Preprint
HUTP-93/A03
De Sitter Waves and the Zero Curvature Limit
We show that a particular set of global modes for the massive de Sitter
scalar field (the de Sitter waves) allows to manage the group representations
and the Fourier transform in the flat (Minkowskian) limit. This is in
opposition to the usual acceptance based on a previous result, suggesting the
appearance of negative energy in the limit process. This method also confirms
that the Euclidean vacuum, in de Sitter spacetime, has to be preferred as far
as one wishes to recover ordinary QFT in the flat limit.Comment: 9 pages, latex no figure, to appear in Phys. Rev.
Vacuum Ambiguity in de Sitter Space at Strong Coupling
It is well known that in the weak coupling regime, quantum field theories in
de Sitter space do not have a unique vacuum, but a class of vacua parametrized
by a complex parameter , i.e., the so-called -vacua. In this
article, using gauge/gravity duality, we calculate the symmetric two-point
function of strongly coupled supersymmetric Yang-Mills theory on
. We find that there is a class of de Sitter invariant vacua,
parametrized by a set of complex parameters .Comment: 17 pages in JHEP style, references adde
Color-Octet Charmonium Production in Top Quark Decays
We calculate the direct production rate of in top quark decays. The
color-octet production via is shown to
have a large branching ratio of order , which is over an
order of magnitude higher than that of the color-singlet production
via or
followed by . This result can be used as a
powerful tool to test the importance of the color-octet mechanism in heavy
quarkonium production.Comment: 10 pages LaTex (2 figures in PS-file
Boson--fermion bound states in two dimensional QCD
We derive the boson--fermion bound state equation in a two dimensional gauge
theory in the large--\nc limit. We analyze the properties of this equation
and in particular, find that the mass trajectory is linear with respect to the
bound state level for the higher mass states.Comment: 5pp, 2 figs (as a separate file), TIT/HEP-23
On Thermalization in de Sitter Space
We discuss thermalization in de Sitter space and argue, from two different
points of view, that the typical time needed for thermalization is of order
, where is the radius of the de Sitter space in question.
This time scale gives plenty of room for non-thermal deviations to survive
during long periods of inflation. We also speculate in more general terms on
the meaning of the time scale for finite quantum systems inside isolated boxes,
and comment on the relation to the Poincar\'{e} recurrence time.Comment: 14 pages, 2 figures, latex, references added. Improved discussion in
section 3 adde
CP violation in gauge theories
We define the CP transformation properties of scalars, fermions and vectors
in a gauge theory and show that only three types of interactions can lead to CP
violation: scalar interactions, fermion-scalar interactions and
associated with the strong CP problem and which involve only the gauge fields.
For technicolor theories this implies the absence of CP violation within
perturbation theory.Comment: 5 pages, 1 figure, revtex and epsf require
Production of neutral scalar Higgs bosons at colliders
We study the production of neutral scalar (CP even) Higgs bosons in the
process by including supersymmetric corrections to the
dominant -channel photon exchange amplitude. In addition to the standard
model and fermion loops, there are substantial contributions from
chargino loops. For some cases, these contributions can exceed those of the
's and ordinary fermions. The cross sections in this channel are generally
one or two orders of magnitude larger than those in the related channel
.Comment: 12 pages RevTeX, 5 postscript figures included, uses epsf.st
On the consistency of de Sitter vacua
In this paper the consistency of the de Sitter invariant -vacua,
which have been introduced as simple tools to study the effects of
transplanckian physics, is investigated. In particular possible non
renormalization problems are discussed, as well as non standard properties of
Greens functions. We also discuss the non thermal properties of the -vacua and the necessity of to change. The conclusion is that non of
these problems necessarily exclude an application of the -vacua to
inflation.Comment: 12 pages, v2: minor clarifications and corrections to reference
Topological Excitations in Compact Maxwell-Chern-Simons Theory
We construct a lattice model of compact (2+1)-dimensional Maxwell-Chern-
Simons theory, starting from its formulation in terms of gauge invariant
quantities proposed by Deser and Jackiw. We thereby identify the topological
excitations and their interactions. These consist of monopolo- antimonopole
pairs bounded by strings carrying both magnetic flux and electric charge. The
electric charge renders the Dirac strings observable and endows them with a
finite energy per unit length, which results in a linearly confining string
tension. Additionally, the strings interact via an imaginary, topological term
measuring the (self-) linking number of closed strings.Comment: harvmac, CERN-TH. 6906/93, DFUPG 80/9
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