4,818 research outputs found
Classical trajectories and quantum supersymmetry
We analyze a supersymmetric system with four flat directions. We observe
several interesting properties, such as the coexistence of the discrete and
continuous spectrum in the same range of energies. We also solve numerically
the classical counterpart of this system. A similar analysis is then done for
an alike, but non-supersymmetric system. The comparison of theses classical and
quantum results may serve as a suggestion about classical manifestations of
supersymmetry.Comment: 16 pages, 12 figures, 5 tables, some misspellings correcte
On the vacuum of the minimal nonsupersymmetric SO(10) unification
We study a class of nonsupersymmetric SO(10) grand unified scenarios where
the first stage of the symmetry breaking is driven by the vacuum expectation
values of the 45-dimensional adjoint representation. Three decade old results
claim that such a Higgs setting may lead exclusively to the flipped SU(5) x
U(1) intermediate stage. We show that this conclusion is actually an artifact
of the tree level potential. The study of the accidental global symmetries
emerging in various limits of the scalar potential offers a simple
understanding of the tree level result and a rationale for the drastic impact
of quantum corrections. We scrutinize in detail the simplest and paradigmatic
case of the 45_{H} + 16_{H} Higgs sector triggering the breaking of SO(10) to
the standard electroweak model. We show that the minimization of the one-loop
effective potential allows for intermediate SU(4)_C x SU(2)_L x U(1)_R and
SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L} symmetric stages as well. These are
the options favoured by gauge unification. Our results, that apply whenever the
SO(10) breaking is triggered by , open the path for hunting the simplest
realistic scenario of nonsupersymmetric SO(10) grand unification.Comment: 22 pages, 1 figure. Refs added. To appear in Phys. Rev.
Complementary colors of colorons: the elementary excitations of the SU(3) Haldane--Shastry model
We propose two possible trial wave functions for the elementary excitations
of the SU(3) Haldane--Shastry model, but then argue on very general grounds
that only one or the other can be a valid excitation. We then prove explicitly
that the trial wave function describing a coloron excitation which transforms
according to representation under SU(3) rotations if the spins of the
original model transform according to representation 3, is exact. If a basis
for the spins on the chain is spanned by the colors blue, red, and green, a
basis for the coloron excitations is hence given by the complementary colors
yellow, cyan, and magenta. We obtain the dispersion and the exclusion
statistics among polarized colorons. Furthermore, we compare our results with
the asymptotic Bethe Ansatz and discuss the generalization to SU()
Bypassing the axial anomalies
Many meson processes are related to the U_A(1) axial anomaly, present in the
Feynman graphs where fermion loops connect axial vertices with vector vertices.
However, the coupling of pseudoscalar mesons to quarks does not have to be
formulated via axial vertices. The pseudoscalar coupling is also possible, and
this approach is especially natural on the level of the quark substructure of
hadrons. In this paper we point out the advantages of calculating these
processes using (instead of the anomalous graphs) the Feynman graphs where
axial vertices are replaced by pseudoscalar vertices. We elaborate especially
the case of the processes related to the Abelian axial anomaly of QED, but we
speculate that it seems possible that effects of the non-Abelian axial anomaly
of QCD can be accounted for in an analogous way.Comment: 12 pages, 4 figures, uses ws-ijmpa.cls, published in the proceedings
of MRST 2005 conference, Utica, New York, 16-18 May 200
Comment on "The Phenomenology of a Nonstandard Higgs Boson in W_L W_L Scattering"
We show that in Composite Higgs models, the coupling of the Higgs resonance
to a pair of bosons is weaker than the corresponding Standard Model
coupling, provided the Higgs arises from electroweak doublets only. This is
partly due to the effects of the nonlinear realization of the chiral symmetries
at the compositeness scale.Comment: 6 pages, BU-HEP 94-2
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
Comparison of 1/mQ^2 Corrections in Mesons and Baryons
We extend our relativistic quark model to the study of the decay Lambda_b ->
Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry
constraints at order 1/mQ^2. We isolate a strong dependence on a parameter
which measures the relative distortion in the light-quark wave functions of the
Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be
small. The dependence on a corresponding parameter in the meson case leads to
large 1/mQ^2 corrections.Comment: 9 pages, LaTeX, 3 self-contained LaTeX figures in separate fil
A QCD Axion from Higher Dimensional Gauge Field
We point out that a QCD axion solving the strong CP problem can arise
naturally from parity-odd gauge field C_M in 5-dimensional (5D) orbifold field
theory. The required axion coupling to the QCD anomaly comes from the 5D
Chern-Simons coupling, and all other unwanted U(1)_{PQ} breaking axion
couplings can be avoided naturally by the 5D gauge symmetry of C_M and the 5D
locality. If the fifth dimension is warped, the resulting axion scale is
suppressed by small warp factor compared to the Planck scale, thereby the model
can generate naturally an intermediate axion scale f_a=10^{10} - 10^{12}GeV.Comment: 5 pages, Revtex
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
Intermediate left-right gauge symmetry, unification of couplings and fermion masses in SUSY
If left-right gauge theory occurs as an intermediate symmetry in a GUT then,
apart from other advantages, it is possible to obtain the see-saw scale
necessary to understand small neutrino masses with Majorana coupling of order
unity. Barring threshold or non-renormalizable gravitational effects, or
assumed presence of additional light scalar particles of unprescribed origin,
all other attempts to achieve manifest one-loop gauge coupling unification in
SUSY SO(10) with left-right intermediate symmetry have not been successful so
far. Attributing this failure to lack of flavor symmetry in the GUT, we show
how the spontaneous symmetry breaking of leads to such
intermediate scale extending over a wide range, GeV
to GeV. All the charged fermion masses are fitted at the see-saw
scale, GeV which is obtained with
Majorana coupling . Using a constrained parametrization in which
CP-violation originates only from quark sector, besides other predictions made
in the neutrino sector, the reactor mixing angle is found to be which is in the range accessible to ongoing and
planned experiments. The leptonic Dirac phase turns out to be radians with Jarlskog invariant .Comment: Minor clarification and few references added to match the published
versio
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