65 research outputs found
A Note On R-Parity Violation and Fermion Masses
We consider a class of supersymmetric SU(3)\times SU(2)\times U(1) multihiggs
models in which R-parity is violated through bilinear Higgs-lepton
interactions. The required, due to R-parity violation, higgs-lepton rotations
introduce an alternative way to generate the phenomenologically desirable
fermion mass matrix structures independently of the equality of Yukawas,
possibly imposed by superstring or other unification.Comment: 8 pages, uses LaTeX2
Quantum Pieri rules for isotropic Grassmannians
We study the three point genus zero Gromov-Witten invariants on the
Grassmannians which parametrize non-maximal isotropic subspaces in a vector
space equipped with a nondegenerate symmetric or skew-symmetric form. We
establish Pieri rules for the classical cohomology and the small quantum
cohomology ring of these varieties, which give a combinatorial formula for the
product of any Schubert class with certain special Schubert classes. We also
give presentations of these rings, with integer coefficients, in terms of
special Schubert class generators and relations.Comment: 59 pages, LaTeX, 6 figure
Stable Grothendieck polynomials and K-theoretic factor sequences
We formulate a nonrecursive combinatorial rule for the expansion of the stable Grothendieck polynomials of [Fomin-Kirillov '94] in the basis of stable Grothendieck polynomials for partitions. This gives a common generalization, as well as new proofs of the rule of [Fomin-Greene '98] for the expansion of the stable Schubert polynomials into Schur polynomials, and the K-theoretic Grassmannian Littlewood-Richardson rule of [Buch '02]. The proof is based on a generalization of the Robinson-Schensted and Edelman-Greene insertion algorithms. Our results are applied to prove a number of new formulas and properties for K-theoretic quiver polynomials, and the Grothendieck polynomials of [Lascoux-Schutzenberger '82]. In particular, we provide the first -theoretic analogue of the factor sequence formula of [Buch-Fulton '99] for the cohomological quiver polynomials
The Fermat-Torricelli problem in normed planes and spaces
We investigate the Fermat-Torricelli problem in d-dimensional real normed
spaces or Minkowski spaces, mainly for d=2. Our approach is to study the
Fermat-Torricelli locus in a geometric way. We present many new results, as
well as give an exposition of known results that are scattered in various
sources, with proofs for some of them. Together, these results can be
considered to be a minitheory of the Fermat-Torricelli problem in Minkowski
spaces and especially in Minkowski planes. This demonstrates that substantial
results about locational problems valid for all norms can be found using a
geometric approach
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Market conditions, trader types and price–volume relation in energy futures markets
We investigate the asymmetric relations between trading volume and price changes, and trading volume and price volatility of energy futures contracts across maturities and under different market conditions. Using a relatively long sample of daily observations, we examine whether the impact of trading volume on returns and volatility of futures contracts can be time-varying and dependent on the market condition. We differentiate the market condition based on the slope of the forward curve into backwardation and contango. The results indicate that trading volume and returns are positively related when the market is in backwardation and negatively related when the market is in contango. In addition, the positive relation between changes in trading volume and volatility of futures contracts seem to be stronger when the market is in backwardation than when it is in contango. Finally, the results indicate that, to a certain extent, trade participation and trading activities of agents in energy futures markets can be explained by the slope of the forward curve which reflects the market condition and sentiment
Constraints on R-parity violating supersymmetry from leptonic and semileptonic tau, B_d and B_s decays
We put constraints on several products of R-parity violating lambda lambda'
and lambda' lambda' type couplings from leptonic and semileptonic tau, B_d and
B_s decays. Most of them are one to two orders of magnitude better than the
existing bounds, and almost free from theoretical uncertainties. A significant
improvement of these bounds can be made in high luminosity tau-charm or B
factories.Comment: 14 pages, latex. A few references added, two typos corrected. Version
to be published in Physical Review
B-physics constraints on baryon number violating couplings: grand unification or R-parity violation
We investigate the role that baryon number violating interactions may play in
phenomenology. Present in various grand unified theories, supersymmetric
theories with R-parity violation and composite models, a diquark state could be
quite light. Using the data on B decays as well as mixing, we
find strong constraints on the couplings that such a light diquark state may
have with the Standard Model quarks.Comment: 19 pages, latex, no figures, 13 tables include
Suppressing dimension-5 operators in general SU(5) models
We discuss dimension-5 operators in supersymmetric models containing extra
hypercharge 1/3 color-triplets. We derive a general formula relating
dimension-5 operator to the color-triplet mass matrix. We show that certain
zeros in the triplet mass-matrix together with some triplet coupling selection
rules can lead to elimination of dimension-5 operators. In particular we focus
on SU(5) models and show that (a) Dimension-5 operators can be eliminated in
the standard SU(5) model by the introduction of an extra pair of 5+5b Higgses
with specific couplings (b) Flipped SU(5) models with extra 10+10b Higgses are
free of dimension-5 operators (c) Flipped SU(5) models with extra 5+5b and/or
extra 10+10b Higgses can be made free of dimension-5 operators for a textured
form of the triplet mass-matrix accompanied by constraints on the 5-plet
couplings to matter. Our analysis is motivated by the recently put forward
M-theory phenomenological framework that requires a strong string coupling and
reintroduces the problem of eliminating dimension-5 operators.Comment: 10 pages, Latex2e, minor changes, references adde
b-tau Unification and neutrino masses in SU(5) extensions of the MSSM with radiative electroweak symmetry breaking
We make a complete analysis of the Yukawa coupling unification in SU(5)
extensions of the MSSM in the framework of the radiative symmetry breaking
scenario. Both logarithmic and finite threshold corrections of sparticles have
been included in the determination of the gauge and Yukawa couplings at M_Z.
The effect of the heavy masses of each model in the renormalization group
equations is also included. We find that in the minimal SU(5) model b-tau
Yukawa unification can be achieved for too large a value of alpha_s. On the
other hand the Peccei-Quinn version of the Missing Doublet model, with the
effect of the right handed neutrino also included, exhibits b-tau unification
in excellent agreement with all low energy experimental data. Unification of
all Yukawa couplings is also discussed.Comment: 20 pages, LaTeX2e,uses psfig,5 figures,full postscript file available
at http://artemis.cc.uoi.gr/~adedes/new97.ps.g
Goldstone Fermion Dark Matter
We propose that the fermionic superpartner of a weak-scale Goldstone boson
can be a natural WIMP candidate. The p-wave annihilation of this `Goldstone
fermion' into pairs of Goldstone bosons automatically generates the correct
relic abundance, whereas the XENON100 direct detection bounds are evaded due to
suppressed couplings to the Standard Model. Further, it is able to avoid
indirect detection constraints because the relevant s-wave annihilations are
small. The interactions of the Goldstone supermultiplet can induce non-standard
Higgs decays and novel collider phenomenology.Comment: 25 pages, 6 figures. References added, minor typos corrected.
Submitted to JHE
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