55,329 research outputs found
The Effect of Spatial Curvature on the Classical and Quantum Strings
We study the effects of the spatial curvature on the classical and quantum
string dynamics. We find the general solution of the circular string motion in
static Robertson-Walker spacetimes with closed or open sections. This is given
closely and completely in terms of elliptic functions. The physical properties,
string length, energy and pressure are computed and analyzed. We find the {\it
back-reaction} effect of these strings on the spacetime: the self-consistent
solution to the Einstein equations is a spatially closed spacetime with
a selected value of the curvature index (the scale f* is normalized to
unity). No self-consistent solutions with exist. We semi-classically
quantize the circular strings and find the mass in each case. For
the very massive strings, oscillating on the full hypersphere, have {\it independent} of and the level spacing {\it
grows} with while the strings oscillating on one hemisphere (without
crossing the equator) have and a {\it finite} number of
states For there are infinitely many string states
with masses that is, the level spacing grows {\it slower} than
The stationary string solutions as well as the generic string fluctuations
around the center of mass are also found and analyzed in closed form.Comment: 30 pages Latex + three tables and five figures (not included
On the connections between Skyrme and Yang Mills theories
Skyrme theories on S^3 and S^2, are analyzed using the generalized zero
curvature in any dimensions. In the first case, new symmetries and integrable
sectors, including the B =1 skyrmions, are unraveled. In S^2 the relation to
QCD suggested by Faddeev is discussedComment: Talk at the Workshop on integrable theories, solitons and duality.
IFT Sao Paulo July 200
Tau-functions and Dressing Transformations for Zero-Curvature Affine Integrable Equations
The solutions of a large class of hierarchies of zero-curvature equations
that includes Toda and KdV type hierarchies are investigated. All these
hierarchies are constructed from affine (twisted or untwisted) Kac-Moody
algebras~. Their common feature is that they have some special ``vacuum
solutions'' corresponding to Lax operators lying in some abelian (up to the
central term) subalgebra of~; in some interesting cases such subalgebras
are of the Heisenberg type. Using the dressing transformation method, the
solutions in the orbit of those vacuum solutions are constructed in a uniform
way. Then, the generalized tau-functions for those hierarchies are defined as
an alternative set of variables corresponding to certain matrix elements
evaluated in the integrable highest-weight representations of~. Such
definition of tau-functions applies for any level of the representation, and it
is independent of its realization (vertex operator or not). The particular
important cases of generalized mKdV and KdV hierarchies as well as the abelian
and non abelian affine Toda theories are discussed in detail.Comment: 27 pages, plain Te
Simple quantum model for light depolarization
Depolarization of quantum fields is handled through a master equation of the
Lindblad type. The specific feature of the proposed model is that it couples
dispersively the field modes to a randomly distributed atomic reservoir, much
in the classical spirit of dealing with this problem. The depolarizing dynamics
resulting from this model is analyzed for relevant states.Comment: Improved version. Accepted for publication in the Journal of the
Optical Society of America
Renormalization Group and Grand Unification with 331 Models
By making a renormalization group analysis we explore the possibility of
having a 331 model as the only intermediate gauge group between the standard
model and the scale of unification of the three coupling constants. We shall
assume that there is no necessarily a group of grand unification at the scale
of convergence of the couplings. With this scenario, different 331 models and
their corresponding supersymmetric versions are considered, and we find the
versions that allow the symmetry breaking described above. Besides, the allowed
interval for the 331 symmetry breaking scale, and the behavior of the running
coupling constants are obtained. It worths saying that some of the
supersymmetric scenarios could be natural frameworks for split supersymmetry.
Finally, we look for possible 331 models with a simple group at the grand
unification scale, that could fit the symmetry breaking scheme described above.Comment: 18 pages. 3 figures. Some results reinterpreted, a new section and
references added. Version to appear in International Journal of Modern
Physics
Canonical Seesaw Mechanism in Electro-Weak SU(4)L x U(1)Y Models
In this paper we prove that the canonical seesaw mechanism can naturally be
implemented in a particular class of electro-weak SU(4)L x U(1)Y gauge models.
The resulting neutrino mass spectrum is determined by just tuning a unique free
parameter 'a' within the algebraical method of solving gauge models with high
symmetries. All the Standard Model phenomenology is preserved, being unaffected
by the new physics occuring at a high breaking scale m ~ 10^11GeV.Comment: 12 pages, 1 Table, no figure
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