363 research outputs found
Cosmology in a brane-universe
This contribution presents the cosmological models with extra dimensions that
have been recently elaborated, which assume that ordinary matter is confined on
a surface, called brane, embedded in a higher dimensional spacetime.Comment: 12 pages; Invited review talk at the JENAM 2002 workshop on "The
cosmology of extra dimensions and varying fundamental constants", Porto,
Portugal, September 200
A Note on the Generalized Friedmann Equations for a Thick Brane
Within our thick brane approach previously used to obtain the cosmological
evolution equations on a thick brane embedded in a five-dimensional
Schwarzschild Anti-de Sitter spacetime it is explicitly shown that the
consistency of these equations with the energy conservation equation requires
that, in general, the thickness of the brane evolves in time. This varying
brane thickness entails the possibility that both Newton's gravitational
constant and the effective cosmological constant are time
dependent.Comment: 6 pages,To appear in GR
Gaugino Condensation in N=1 Supergravity Models with Multiple Dilaton-Like Fields
We study supersymmetry breaking by hidden-sector gaugino condensation in N=1
D=4 supergravity models with multiple dilaton-like moduli fields. Our work is
motivated by Type I string theory, in which the low-energy effective Lagrangian
can have different dilaton-like fields coupling to different sectors of the
theory. We construct the effective Lagrangian for gaugino condensation and use
it to compute the visible-sector gaugino masses. We find that the gaugino
masses can be of order the gravitino mass, in stark contrast to heterotic
string models with a single dilaton field.Comment: LaTeX, 17 pages, 2 eps figure
Cosmology and Gravitation: the grand scheme for High-Energy Physics
These lectures describe how the Standard Model of cosmology (CDM)
has developped, based on observational facts but also on ideas formed in the
context of the theory of fundamental interactions, both gravitational and
nongravitational, the latter being described by the Standard Model of high
energy physics. It focuses on the latest developments, in particular the
precise knowledge of the early Universe provided by the observation of the
Cosmic Microwave Background and the discovery of the present acceleration of
the expansion of the Universe. While insisting on the successes of the Standard
Model of cosmology, we will stress that it rests on three pillars which involve
many open questions: the theory of inflation, the nature of dark matter and of
dark energy. We will devote one chapter to each of these issues, describing in
particular how this impacts our views on the theory of fundamental
interactions. More technical parts are given in italics. They may be skipped
altogether.Comment: 75 pages, contribution to the 2012 European School of High-Energy
Physics, La Pommeraye, Anjou, France, 06-19 Jun 2012, edited by C. Grojean
and M. Mulder
Gaugino condensation and the anomalous
We study gaugino condensation in presence of an anomalous gauge group
and find that global supersymmetry is dynamically broken. An example of
particular interest is provided by effective string models with 4-dimensional
Green-Schwarz anomaly cancellation mechanism. The structure of the hidden
sector is constrained by the anomaly cancellation conditions and the scale of
gaugino condensation is shifted compared with the usual case. We explicitly
compute the resulting soft supersymmetry breaking terms.Comment: 13 page
Dilaton, moduli and string/five-brane duality as seen from four dimensions
A naive dimensional reduction of the supergravity theory that
naturally arises in five-brane models is used to determine the r\^ole of two
fields which are basic ingredients of string models: the dilaton and, among the
moduli, the breathing mode. It is shown that, under the duality transformation
that relates five-branes and strings, these two fields exchange the r\^oles of
10-dimensional dilaton and radius of the compact manifold. A description of
this phenomenon in terms of the linear multiplets of the 4-dimensional
supergravity is also presented.Comment: 14 pages, Latex, NSF-ITP-93-6
Self-Duality in Nonlinear Electromagnetism
We discuss duality invariant interactions between electromagnetic fields and
matter. The case of scalar fields is treated in some detail.Comment: 10 pages, full postscript also available from
http://theor1.lbl.gov/www/theorygroup/papers/40770.p
Global vs local cosmic strings from pseudo-anomalous U(1)
We study the structure of cosmic strings produced at the breaking of an
anomalous U(1) gauge symmetry present in many superstring compactification
models. We show that their coupling with the axion necessary in order to cancel
the anomalies does not prevent them from being local, even though their energy
per unit length is found to diverge logarithmically. We discuss the formation
of such strings and the phenomenological constraints that apply to their
parameters.Comment: 6 pages, uses RevTeX, no figur
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