3,859 research outputs found
Flavor Changing Scalar Interactions
The smallness of fermion masses and mixing angles has recently been been
attributed to approximate global symmetries, one for each fermion type.
The parameters associated with these symmetry breakings are estimated here
directly from observed masses and mixing angles. It turns out that although
flavor changing reaction rates may be acceptably small in electroweak theories
with several scalar doublets without imposing any special symmetries on the
scalars themselves, such theories generically yield too much CP violation in
the neutral kaon mass matrix. Hence in these theories CP must also be a good
approximate symmetry. Such models provide an alternative mechanism for CP
violation and have various interesting phenomenological features.Comment: 18 pages. UTTG-22-92; LBL 33016; UCB 92/3
Gauge Unification In Six Dimensions
We study the breaking of a supersymmetric SO(10) GUT in 6 dimensions by
orbifold compactification. In 4 dimensions we obtain a N=1 supersymmetric
theory with the standard model gauge group enlarged by an additional U(1)
symmetry. The 4-dimensional gauge symmetry is obtained as intersection of the
Pati-Salam and the Georgi-Glashow subgroups of SO(10), which appear as unbroken
subgroups in the two 5 dimensional subspaces, respectively. The doublet-triplet
splitting arises as in the recently discussed SU(5) GUTs in 5 dimensions.Comment: Latex2e, 9 pages, 1 figure; references added, to be published in
Phys. Lett
Flavor Unification and Discrete Nonabelian Symmetries
Grand unified theories with fermions transforming as irreducible
representations of a discrete nonabelian flavor symmetry can lead to realistic
fermion masses, without requiring very small fundamental parameters. We
construct a specific example of a supersymmetric GUT based on the flavor
symmetry --- a subgroup of --- which can explain the
observed quark and lepton masses and mixing angles. The model predicts
and gives a neutrino mass eV, with other neutrino masses much lighter. Combined
constraints of light quark masses and perturbative unification place flavor
symmetry breaking near the GUT scale; it may be possible to probe these
extremely high energies by continuing the search for flavor changing neutral
currents.Comment: 24 pages, UCSD-PTH-93-30 (uuencoded file; requires epsf.tex,
available from this bulletin board
Finestructure and microstructure in the North Atlantic Current
The relationship between intrusive finestructure and optical microstructure was studied by simultaneous CTD Tow-yos and deployments of the shadowgraph profiler SCIMP. Strong thermohaline intrusions, 5 to 50 m thick, were tracked laterally for 5 to 10 km in the front associated with the North Atlantic Current...
Effective Lagrangians and Parity-Conserving Time-Reversal Violation at Low Energies
Using effective Lagrangians, we argue that any time-reversal-violating but
parity-conserving effects are too small to be observed in flavor-conserving
nuclear processes without dramatic improvement in experimental accuracy. In the
process we discuss other arguments that have appeared in the literature.Comment: Revised manuscript, 11 pages, RevTex, epsf.st
A Topcolor Jungle Gym
We discuss an alternative to the topcolor seesaw mechanism. In our scheme,
all the light quarks carry topcolor, and there are many composite SU(2)
doublets. This makes it possible to get the observed top quark mass and
observed breaking in a way that is quite different from the
classic seesaw mechanism. We discuss a model of this kind that arises naturally
in the context of dynamically broken topcolor. There are many composite scalars
in a theory of this kind. This has important effects on the Pagels-Stokar
relation and the Higgs mass. We find GeV, lighter than in
typical topcolor models. We also show that the electroweak singlet quarks in
such a model can be lighter than the corresponding quarks in a seesaw model.Comment: 23 pages, LaTeX, uses epsf and psfi
Invariant Operators in Collinear Effective Theory
We consider processes which produce final state hadrons whose energy is much
greater than their mass. In this limit interactions involving collinear
fermions and gluons are constrained by a symmetry, and we give a general set of
rules for constructing leading and subleading invariant operators. Wilson
coefficients C(mu,P) are functions of a label operator P, and do not commute
with collinear fields. The symmetry is used to reproduce a two-loop result for
factorization in B -> D pi in a simple way.Comment: 11 pages, 2 figs, journal versio
Renormalization of initial conditions and the trans-Planckian problem of inflation
Understanding how a field theory propagates the information contained in a
given initial state is essential for quantifying the sensitivity of the cosmic
microwave background to physics above the Hubble scale during inflation. Here
we examine the renormalization of a scalar theory with nontrivial initial
conditions in the simpler setting of flat space. The renormalization of the
bulk theory proceeds exactly as for the standard vacuum state. However, the
short distance features of the initial conditions can introduce new divergences
which are confined to the surface on which the initial conditions are imposed.
We show how the addition of boundary counterterms removes these divergences and
induces a renormalization group flow in the space of initial conditions.Comment: 22 pages, 4 eps figures, uses RevTe
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