499 research outputs found
The size of flavor changing effects induced by the symmetry breaking sector
It has recently been shown that strong interactions underlying electroweak
symmetry breaking will induce four-fermion amplitudes proportional to m_t^2,
which in turn will influence a variety of flavor changing processes. We argue
that the size of these effects are likely to be far below the current
experimental bounds.Comment: 5 pages, LaTeX, 1 figur
Cosmic balloons
Cosmic balloons, consisting of relativistic particles trapped inside a
spherical domain wall, may be created in the early universe. We calculate the
balloon mass as a function of the radius and the energy density
profile, , including the effects of gravity. At the maximum balloon
mass for any value of the mass density of the wall.Comment: 9 pages, LaTeX, 2 figures in separate file, UPTP-93-1
Effects of technicolor on standard model running couplings
We discuss the running couplings in the standard model, SU(3SU(2U(1, when the Higgs sector is replaced by SU(
technicolor. Particular attention is given to the running of the couplings at
momentum scales where technicolor is nonperturbative, and in this region we
apply a relativistic constituent technifermion model. This model has been
tested against the known running of the QED coupling due to nonperturbative
QCD. An understanding of this low momentum running allows the calculation of
the couplings at a higher scale, , where technicolor becomes
perturbative. We provide numerical values for the changes in the three standard
model couplings between and due to technicolor, assuming
separately ``one doublet'' and ``one family'' technicolor models. The
distinction between a running and walking technicolor coupling is also
considered.Comment: 14 pages of LaTeX, UTPT-94-
Trouble for MAC
We show that the next-to-leading corrections to the kernel of the gap
equation can be large and of opposite sign to the lowest order kernel, in the
presence of a gauge boson mass. This calls into question the reliability of the
Most Attractive Channel hypothesis.Comment: 8 pages, 1 figure, LaTe
Calculation of the Chiral Lagrangian Coefficients from the Underlying Theory of QCD: A Simple Approach
We calculate the coefficients in the chiral Lagrangian approximately from QCD
based on a previous study of deriving the chiral Lagrangian from the first
principles of QCD in which the chiral Lagrangian coefficients are defined in
terms of certain Green's functions in QCD. We first show that, in the large
N(c)-limit, the anomaly part contributions to the coefficients are exactly
cancelled by certain terms in the normal part contributions, and the final
results of the coefficients only concern the remaining normal part
contributions depending on QCD interactions. We then do the calculation in a
simple approach with the approximations of taking the large-N(c) limit, the
leading order in dynamical perturbation theory, and the improved ladder
approximation, thereby the relevant Green's functions are expressed in terms of
the quark self energy. By solving the Schwinger-Dyson equation for the quark
self energy, we obtain the approximate QCD predicted coefficients and the quark
condensate which are consistent with the experimental values.Comment: Further typos corrected, to appear in Phys. Rev.
Charged Vacuum Bubble Stability
A type of scenario is considered where electrically charged vacuum bubbles,
formed from degenerate or nearly degenerate vacuua separated by a thin domain
wall, are cosmologically produced due to the breaking of a discrete symmetry,
with the bubble charge arising from fermions residing within the domain wall.
Stability issues associated with wall tension, fermion gas, and Coulombic
effects for such configurations are examined. The stability of a bubble depends
upon parameters such as the symmetry breaking scale and the fermion coupling. A
dominance of either the Fermi gas or the Coulomb contribution may be realized
under certain conditions, depending upon parameter values.Comment: 16 pages,revtex; accepted for publication in Phys.Rev.
Are Four-Fermion Operators Relevant for the Fermion Mass Problem?
Four-fermion operators may have large anomalous scaling and become relevant
operators in some strongly interacting gauge theories. We present a detailed
model which illustrates some of the implications of such operators for the
generation of quark and lepton masses. Such operators would originate at high
scales where quarks and leptons experience a new strong interaction, but no
unbroken technicolor interaction is required. The breakdown of both the new
gauge symmetry and electroweak gauge symmetry is associated with a dynamical
TeV mass for fourth family quarks. Among the new physics signatures are
anomalous (chromo)magnetic moments and their flavor-changing counterparts.Comment: 23 pages, postscript, version to be published in PRD, PDF file is
available at http://miteymac.physics.utoronto.ca/bh/papers/papers.htm
CP Violation from the Neutrino Sector: A Case for the Superweak Model
We discuss how CP violation originating in the right-handed neutrino sector
can feed into the quark sector, in an otherwise CP invariant theory. The
dominant effects are superweak, and we suggest that this may yield a natural
resolution of the strong CP problem. This work builds on and extends a
previously proposed model of quark and lepton masses, based on a new strong
flavor interaction above the weak scale.Comment: 15 pages, LaTeX, version to be published in PR
Chiral Symmetry Breaking via Multi-fermion Green Functions
Previous results on fermion chirality-flipping four-point functions are
extended to gauge theories. The problem is purely non-perturbative, and
it is approached by truncating the Schwinger-Dyson hierarchy. The large-
limit also simplifies the problem substantially. The resulting equation is
solved numerically by relaxation techniques and an estimate of the critical
coupling and momentum behavior is obtained. We also comment on the behavior of
chirality-flipping -point functions for general .Comment: 17 pages, LaTeX + 3 figures, version to be publishe
Derivation of the Effective Chiral Lagrangian for Pseudoscalar Mesons from QCD
We formally derive the chiral Lagrangian for low lying pseudoscalar mesons
from the first principles of QCD considering the contributions from the normal
part of the theory without taking approximations. The derivation is based on
the standard generating functional of QCD in the path integral formalism. The
gluon-field integration is formally carried out by expressing the result in
terms of physical Green's functions of the gluon. To integrate over the
quark-field, we introduce a bilocal auxiliary field Phi(x,y) representing the
mesons. We then develop a consistent way of extracting the local pseudoscalar
degree of freedom U(x) in Phi(x,y) and integrating out the rest degrees of
freedom such that the complete pseudoscalar degree of freedom resides in U(x).
With certain techniques, we work out the explicit U(x)-dependence of the
effective action up to the p^4-terms in the momentum expansion, which leads to
the desired chiral Lagrangian in which all the coefficients contributed from
the normal part of the theory are expressed in terms of certain Green's
functions in QCD. Together with the existing QCD formulae for the anomaly
contributions, the present results leads to the complete QCD definition of the
coefficients in the chiral Lagrangian. The relation between the present QCD
definition of the p^2-order coefficient F_0^2 and the well-known approximate
result given by Pagels and Stokar is discussed.Comment: 16 pages in RevTex, some typos are corrected, version for publication
in Phys. Rev.
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