844 research outputs found
The Exact MSSM Spectrum from String Theory
We show the existence of realistic vacua in string theory whose observable
sector has exactly the matter content of the MSSM. This is achieved by
compactifying the E_8 x E_8 heterotic superstring on a smooth Calabi-Yau
threefold with an SU(4) gauge instanton and a Z_3 x Z_3 Wilson line.
Specifically, the observable sector is N=1 supersymmetric with gauge group
SU(3)_C x SU(2)_L x U(1)_Y x U(1)_{B-L}, three families of quarks and leptons,
each family with a right-handed neutrino, and one Higgs-Higgs conjugate pair.
Importantly, there are no extra vector-like pairs and no exotic matter in the
zero mode spectrum. There are, in addition, 6 geometric moduli and 13 gauge
instanton moduli in the observable sector. The holomorphic SU(4) vector bundle
of the observable sector is slope-stable.Comment: 15 pages, LaTeX; v2: Hidden sector is unstable, symbol typesetting
error corrected, clarifications and references added; v3: New discussion of
hidden secto
Moduli Dependent mu-Terms in a Heterotic Standard Model
In this paper, we present a formalism for computing the non-vanishing Higgs
mu-terms in a heterotic standard model. This is accomplished by calculating the
cubic product of the cohomology groups associated with the vector bundle moduli
(phi), Higgs (H) and Higgs conjugate (Hbar) superfields. This leads to terms
proportional to phi H Hbar in the low energy superpotential which, for non-zero
moduli expectation values, generate moduli dependent mu-terms of the form
H Hbar. It is found that these interactions are subject to two very restrictive
selection rules, each arising from a Leray spectral sequence, which greatly
reduce the number of moduli that can couple to Higgs-Higgs conjugate fields. We
apply our formalism to a specific heterotic standard model vacuum. The
non-vanishing cubic interactions phi H Hbar are explicitly computed in this
context and shown to contain only four of the nineteen vector bundle moduli.Comment: 23 pages, LaTe
Smooth Fano polytopes whose Ehrhart polynomial has a root with large real part
The symmetric edge polytopes of odd cycles (del Pezzo polytopes) are known as
smooth Fano polytopes. In this paper, we show that if the length of the cycle
is 127, then the Ehrhart polynomial has a root whose real part is greater than
the dimension. As a result, we have a smooth Fano polytope that is a
counterexample to the two conjectures on the roots of Ehrhart polynomials.Comment: 4 pages, We changed the order of the auhors and omitted a lot of
parts of the paper. (If you are interested in omitted parts, then please read
v1
Stability of the Minimal Heterotic Standard Model Bundle
The observable sector of the "minimal heterotic standard model" has precisely
the matter spectrum of the MSSM: three families of quarks and leptons, each
with a right-handed neutrino, and one Higgs-Higgs conjugate pair. In this
paper, it is explicitly proven that the SU(4) holomorphic vector bundle leading
to the MSSM spectrum in the observable sector is slope-stable.Comment: LaTeX, 19 page
Yukawa Couplings in Heterotic Standard Models
In this paper, we present a formalism for computing the Yukawa couplings in
heterotic standard models. This is accomplished by calculating the relevant
triple products of cohomology groups, leading to terms proportional to Q*H*u,
Q*Hbar*d, L*H*nu and L*Hbar*e in the low energy superpotential. These
interactions are subject to two very restrictive selection rules arising from
the geometry of the Calabi-Yau manifold. We apply our formalism to the
"minimal" heterotic standard model whose observable sector matter spectrum is
exactly that of the MSSM. The non-vanishing Yukawa interactions are explicitly
computed in this context. These interactions exhibit a texture rendering one
out of the three quark/lepton families naturally light.Comment: 21 pages, LaTe
Lattice Point Generating Functions and Symmetric Cones
We show that a recent identity of Beck-Gessel-Lee-Savage on the generating
function of symmetrically contrained compositions of integers generalizes
naturally to a family of convex polyhedral cones that are invariant under the
action of a finite reflection group. We obtain general expressions for the
multivariate generating functions of such cones, and work out the specific
cases of a symmetry group of type A (previously known) and types B and D (new).
We obtain several applications of the special cases in type B, including
identities involving permutation statistics and lecture hall partitions.Comment: 19 page
High resolution studies of low-energy electron attachment to SF5Cl: Product anions and absolute cross sections
Low energy electron attachment to SFCl was studied at high energy resolution by mass spectrometric detection of the product anions. Two variants of the laser photoelectron attachment (LPA) technique (Kaiserslautern) were used for determining the threshold behaviour of the yield for SF formation at about 1 meV resolution, and to investigate the relative cross sections for Cl, FCl, and SF formation towards higher energies (up to 1 eV) at about 20 meV resolution. Thermal swarm measurements (Birmingham) were used to place the relative LPA cross sections on an absolute scale. A trochoidal electron monochromator (Innsbruck) was used for survey measurements of the relative cross sections for the different product anions over the energy range of 0-14 eV with a resolution of 0.30 eV. Combined with earlier beam data (taken at Berlin, J. Chem. Phys. 88 (1988) 149), the present experimental results provide a detailed set of partial cross sections for anion formation in low-energy electron collisions with SFCl
Heterotic Compactification, An Algorithmic Approach
We approach string phenomenology from the perspective of computational
algebraic geometry, by providing new and efficient techniques for proving
stability and calculating particle spectra in heterotic compactifications. This
is done in the context of complete intersection Calabi-Yau manifolds in a
single projective space where we classify positive monad bundles. Using a
combination of analytic methods and computer algebra we prove stability for all
such bundles and compute the complete particle spectrum, including gauge
singlets. In particular, we find that the number of anti-generations vanishes
for all our bundles and that the spectrum is manifestly moduli-dependent.Comment: 36 pages, Late
A QCD motivated model for soft interactions at high energies
In this paper we develop an approach to soft scattering processes at high
energies,which is based on two mechanisms: Good-Walker mechanism for low mass
diffractionand multi-Pomeron interactions for high mass diffraction. The
pricipal idea, that allows us to specify the theory for Pomeron interactions,
is that the so called soft processes occur at rather short distances
(r^2 \propto 1 /^2 \propto \alpha'_\pom \approx 0.01 GeV^{-2}), where
perturbative QCD is valid. The value of the Pomeron slope \alpha'_\pom was
obtained from the fit to experimental data. Using this theoretical approach we
suggest a model that fits all soft data in the ISR-Tevatron energy range, the
total, elastic, single and double diffractive cross sections, including
dependence of the differential elastic cross section, and the mass dependence
of single diffraction. In this model we calculate the survival probability of
diffractive Higgs production, and obtained a value for this observable, which
is smaller than 1% at the LHC energy range.Comment: 33pp,20 figures in eps file
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