557 research outputs found
Boundary Inflation
Inflationary solutions are constructed in a specific five-dimensional model
with boundaries motivated by heterotic M-theory. We concentrate on the case
where the vacuum energy is provided by potentials on those boundaries. It is
pointed out that the presence of such potentials necessarily excites bulk
Kaluza-Klein modes. We distinguish a linear and a non-linear regime for those
modes. In the linear regime, inflation can be discussed in an effective
four-dimensional theory in the conventional way. We lift a four-dimensional
inflating solution up to five dimensions where it represents an inflating
domain wall pair. This shows explicitly the inhomogeneity in the fifth
dimension. We also demonstrate the existence of inflating solutions with
unconventional properties in the non-linear regime. Specifically, we find
solutions with and without an horizon between the two boundaries. These
solutions have certain problems associated with the stability of the additional
dimension and the persistence of initial excitations of the Kaluza-Klein modes.Comment: 35 pages, Latex, one eps-figur
Moduli Spaces of Fivebranes on Elliptic Calabi-Yau Threefolds
We present a general method for calculating the moduli spaces of fivebranes
wrapped on holomorphic curves in elliptically fibered Calabi-Yau threefolds, in
particular, in the context of heterotic M theory. The cases of fivebranes
wrapped purely on a fiber curve, purely on a curve in the base and,
generically, on a curve with components both in the fiber and the base are each
discussed in detail. The number of irreducible components of the fivebrane and
their properties, such as their intersections and phase transitions in moduli
space, follow from the analysis. Even though generic curves have a large number
of moduli, we show that there are isolated curves that have no moduli
associated with the Calabi-Yau threefold. We present several explicit examples,
including cases which correspond to potentially realistic three family models
with grand unified gauge group SU(5).Comment: 56 pages, latex2e with amsmath and epsfig, 9 postscript figure
Five--Branes and Supersymmetry Breaking in M--Theory
Supersymmetry breaking via gaugino condensation is studied in vacua of
heterotic M-theory with five-branes. We show that supersymmetry is still broken
by a global mechanism and that the non-perturbative superpotential takes the
standard form. When expressed in terms of low energy fields, a modification
arises due to a threshold correction in the gauge kinetic function that depends
on five-brane moduli. We also determine the form of the low energy matter field
Kahler potential. These results are used to discuss the soft supersymmetry
breaking parameters, in particular the question of universality.Comment: 28 pages, Late
Higher-Derivative Gravitation in Bosonic and Superstring Theories
A discussion of the number of degrees of freedom, and their dynamical
properties, in higher-derivative gravitational theories is presented. The
complete non-linear sigma model for these degrees of freedom is exhibited using
the method of auxiliary fields. As a by-product we present a consistent
non-linear coupling of a spin-2 tensor to gravitation. It is shown that
non-vanishing terms arise in ,
superstring Lagrangians due to one-loop radiative corrections with light field
internal lines.Comment: 8 pages, LaTeX2e and AMS-LaTeX 1.2, Talk presented at SUSY'95, Ecole
Polytechnique in Palaiseau, Palaiseau, France, May 15-19, 199
Non-Perturbative Vacua and Particle Physics in M-Theory
In this letter, we introduce a general theory for the construction of
particle physics theories, with three families and realistic gauge groups,
within the context of heterotic M-theory. This is achieved using semi-stable
holomorphic gauge bundles over elliptically fibered Calabi-Yau three-folds.
Construction of realistic theories is facilitated by the appearance of
non-perturbative five-branes in the vacuum. The complete moduli space of these
five-branes is computed and their worldvolume gauge theory discussed. It is
shown, within the context of holomorphic gauge bundles, how grand unified gauge
groups can be spontaneously broken to the gauge group of the standard model.
These ideas are illustrated in an explicit SU(5) three-family example.Comment: 16 pages, Latex 2e with amsmath, some typos correcte
Holomorphic Vector Bundles and Non-Perturbative Vacua in M-Theory
We review the spectral cover formalism for constructing both U(n) and SU(n)
holomorphic vector bundles on elliptically fibered Calabi-Yau three-folds which
admit a section. We discuss the allowed bases of these three-folds and show
that physical constraints eliminate Enriques surfaces from consideration.
Relevant properties of the remaining del Pezzo and Hirzebruch surfaces are
presented. Restricting the structure group to SU(n), we derive, in detail, a
set of rules for the construction of three-family particle physics theories
with phenomenologically relevant gauge groups. We show that anomaly
cancellation generically requires the existence of non-perturbative vacua
containing five-branes. We illustrate these ideas by constructing four explicit
three-family non-perturbative vacua.Comment: 44 pages, Latex 2e with amsmath, typos correcte
Standard Model Vacua in Heterotic M-Theory
We present a class of N=1 supersymmetric ``standard'' models of particle
physics, derived directly from heterotic M-theory, that contain three families
of chiral quarks and leptons coupled to the gauge group SU(3)_C X SU(2)_L X
U(1)_Y. These models are a fundamental form of ``brane world'' theories, with
an observable and hidden sector each confined, after compactification on a
Calabi--Yau threefold, to a BPS three-brane separated by a higher dimensional
bulk space with size of the order of the intermediate scale. The requirement of
three families, coupled to the fundamental conditions of anomaly freedom and
supersymmetry, constrains these models to contain additional five-branes
located in the bulk space and wrapped around holomorphic curves in the
Calabi--Yau threefold.Comment: 10 pages, Latex file, no figures. Talk given at STRINGS'99, Potsdam,
Germany, July 19-24, 199
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