572 research outputs found
Two-Time Physics with gravitational and gauge field backgrounds
It is shown that all possible gravitational, gauge and other interactions
experienced by particles in ordinary d-dimensions (one-time) can be described
in the language of two-time physics in a spacetime with d+2 dimensions. This is
obtained by generalizing the worldline formulation of two-time physics by
including background fields. A given two-time model, with a fixed set of
background fields, can be gauged fixed from d+2 dimensions to (d-1) +1
dimensions to produce diverse one-time dynamical models, all of which are
dually related to each other under the underlying gauge symmetry of the unified
two-time theory. To satisfy the gauge symmetry of the two-time theory the
background fields must obey certain coupled differential equations that are
generally covariant and gauge invariant in the target d+2 dimensional
spacetime. The gravitational background obeys a null homothety condition while
the gauge field obeys a differential equation that generalizes a similar
equation derived by Dirac in 1936. Explicit solutions to these coupled
equations show that the usual gravitational, gauge, and other interactions in d
dimensions may be viewed as embedded in the higher d+2 dimensional space, thus
displaying higher spacetime symmetries that otherwise remain hidden.Comment: Latex, 19 pages, references adde
Noncommutative Sp(2,R) Gauge Theories - A Field Theory Approach to Two-Time Physics
Phase-space and its relativistic extension is a natural space for realizing
Sp(2,R) symmetry through canonical transformations. On a Dx2 dimensional
covariant phase-space, we formulate noncommutative field theories, where
Sp(2,R) plays a role as either a global or a gauge symmetry group. In both
cases these field theories have potential applications, including certain
aspects of string theories, M-theory, as well as quantum field theories. If
interpreted as living in lower dimensions, these theories realize Poincare'
symmetry linearly in a way consistent with causality and unitarity. In case
Sp(2,R) is a gauge symmetry, we show that the spacetime signature is determined
dynamically as (D-2,2). The resulting noncommutative Sp(2,R) gauge theory is
proposed as a field theoretical formulation of two-time physics: classical
field dynamics contains all known results of `two-time physics', including the
reduction of physical spacetime from D to (D-2) dimensions, with the associated
`holography' and `duality' properties. In particular, we show that the solution
space of classical noncommutative field equations put all massless scalar,
gauge, gravitational, and higher-spin fields in (D-2) dimensions on
equal-footing, reminiscent of string excitations at zero and infinite tension
limits.Comment: 32 pages, LaTe
Black hole entropy reveals a 12th "dimension"
The Beckenstein-Hawking black hole entropy in string theory and its
extensions, as expressed in terms of charges that correspond to central
extensions of the supersymmetry algebra, has more symmetries than U-duality. It
is invariant under transformations of the charges, involving a 12th (or 13th)
``dimension''. This is an indication that the secret theory behind string
theory has a superalgebra involving Lorentz non-scalar extensions (that are not
strictly central), as suggested in S-theory, and which could be hidden in M- or
F- theories. It is suggested that the idea of spacetime is broader than usual,
and that a larger ``spacetime" is partially present in black holes.Comment: Latex, 20 pages, minor formatting correction
Global Analysis of New Gravitational Singularities in String and Particle Theories
We present a global analysis of the geometries that arise in non-compact
current algebra (or gauged WZW) coset models of strings and particles
propagating in curved space-time. The simplest case is the 2d black hole. In
higher dimensions these geometries describe new and much more complex
singularities. For string and particle theories (defined in the text) we
introduce general methods for identifying global coordinates and give the
general exact solution for the geodesics for any gauged WZW model for any
number of dimensions. We then specialize to the 3d geometries associated with
(and also ) and discuss in detail the global
space, geodesics, curvature singularities and duality properties of this space.
The large-small (or mirror) type duality property is reformulated as an
inversion in group parameter space. The 3d global space has two topologically
distinct sectors, with patches of different sectors related by duality. The
first sector has a singularity surface with the topology of ``pinched double
trousers". It can be pictured as the world sheet of two closed strings that
join into a single closed string and then split into two closed strings, but
with a pinch in each leg of the trousers. The second sector has a singularity
surface with the topology of ``double saddle", pictured as the world sheets of
two infinite open strings that come close but do not touch. We discuss the
geodesicaly complete spaces on each side of these surfaces and interpret the
motion of particles in physical terms. A cosmological interpretation is
suggested and comments are mode on possible physical applications.Comment: 31 pages, plus 4 figure
Gravitational instantons and black plane solutions in 4-d string theory
We consider gauged Wess-Zumino models based on the non compact group
. It is shown that by vector gauging the maximal compact subgroup
the resulting backgrounds obey the gravity-dilaton one loop string
vacuum equations of motion in four dimensional euclidean space. The torsionless
solution is then interpreted as a pseudo-instanton of the Liouville
theory coupled to gravity. The presence of a traslational isometry in the model
allows to get another string vacuum backgrounds by using target duality that we
identify with those corresponding to the axial gauging. We also compute the
exact backgrounds. Depending on the value of , they may be interpreted as
instantons connecting a highly singular big bang like universe with a static
singular or regular black plane geometry.Comment: 29 page
Breakdown of large-N quenched reduction in SU(N) lattice gauge theories
We study the validity of the large-N equivalence between four-dimensional
SU(N) lattice gauge theory and its momentum quenched version--the Quenched
Eguchi-Kawai (QEK) model. We find that the assumptions needed for the proofs of
equivalence do not automatically follow from the quenching prescription. We use
weak-coupling arguments to show that large-N equivalence is in fact likely to
break down in the QEK model, and that this is due to dynamically generated
correlations between different Euclidean components of the gauge fields. We
then use Monte-Carlo simulations at intermediate couplings with 20 <= N <= 200
to provide strong evidence for the presence of these correlations and for the
consequent breakdown of reduction. This evidence includes a large discrepancy
between the transition coupling of the "bulk" transition in lattice gauge
theories and the coupling at which the QEK model goes through a strongly
first-order transition. To accurately measure this discrepancy we adapt the
recently introduced Wang-Landau algorithm to gauge theories.Comment: 51 pages, 16 figures, Published verion. Historical inaccuracies in
the review of the quenched Eguchi-Kawai model are corrected, discussion on
reduction at strong-coupling added, references updated, typos corrected. No
changes to results or conclusion
U*(1,1) Noncommutative Gauge Theory As The Foundation of 2T-Physics in Field Theory
A very simple field theory in noncommutative phase space X^{M},P^{M} in d+2
dimensions, with a gauge symmetry based on noncommutative u*(1,1), furnishes
the foundation for the field theoretic formulation of Two-Time Physics. This
leads to a remarkable unification of several gauge principles in d dimensions,
including Maxwell, Einstein and high spin gauge principles, packaged together
into one of the simplest fundamental gauge symmetries in noncommutative quantum
phase space in d+2 dimensions. A gauge invariant action is constructed and its
nonlinear equations of motion are analyzed. Besides elegantly reproducing the
first quantized worldline theory with all background fields, the field theory
prescribes unique interactions among the gauge fields. A matrix version of the
theory, with a large N limit, is also outlinedComment: 24 pages, LaTe
Non-Singularity of the Exact Two-Dimensional String Black Hole
We study the global structure of the exact two-dimensional space-time which
emerges from string theory. Previous work has shown that in the semi-classical
limit, this is a black hole similar to the Schwarzschild solution. However, we
find that in the exact case, a new Euclidean region appears "between" the
singularity and black hole interior. However the boundary between the
Lorentzian and Euclidean regions is a coordinate singularity, which turns out
to be a surface of time reflection symmetry in an extended space-time. Thus
strings having fallen through the black hole horizon would eventually emerge
through another one into a new asymptotically flat region. The maximally
extended space-time consists of an infinite number of universes connected by
wormholes. There are no singularities present in this geometry. We also
calculate the mass and temperature associated with the space-time.Comment: 9 pages, latex, DAMTP R93/
Antisymmetric tensor coupling and conformal invariance in sigma models corresponding to gauged WZNW theories
String backgrounds associated with gauged WZNW models generically
depend on or . The exact expressions for the corresponding
metric G_{\m\n}, antisymmetric tensor B_{\m\n}, and dilaton can be
obtained by eliminating the gauge field from the local part of the
effective action of the gauged WZNW model. We show that there exists a
manifestly gauge-invariant prescription for the derivation of the antisymmetric
tensor coupling. When the subgroup is one-dimensional and is simple the
antisymmetric tensor is given by the semiclassical (-independent)
expression. We consider in detail the simplest non-trivial example with
non-trivial B_{\m\n} -- the D=3 sigma model corresponding to the gauged WZNW theory (`charged black string') and show that the exact
expressions for G_{\m\n}, B_{\m\n} and solve the Weyl invariance
conditions in the two-loop approximation. Similar conclusion is reached for the
closely related chiral gauged WZNW model. We find that there exists
a scheme in which the semiclassical background is also a solution of the
two-loop conformal invariance equations (but the tachyon equation takes a
non-canonical form). We discuss in detail the role of field redefinitions
(scheme dependence) in establishing a correspondence between the sigma model
and conformal field theory results.Comment: 55 pages, harvmac, CERN-TH.6969/93, THU-93/25, Imperial/TP/92-93/59.
(Another prescription for extracting the exact antisymmetric tensor is
described leading to a purely semiclassical expression for it
Relativistic quantum model of confinement and the current quark masses
We consider a relativistic quantum model of confined massive spinning quarks
and antiquarks which describes leading Regge trajectories of mesons. The quarks
are described by the Dirac equations and the gluon contribution is approximated
by the Nambu-Goto straight-line string. The string tension and the current
quark masses are the main parameters of the model. Additional parameters are
phenomenological constants which approximate nonstring short-range
contributions. Comparison of the measured meson masses with the model
predictions allows one to determine the current quark masses (in MeV) to be
. The chiral
model[23] makes it possible to estimate from here the - and -quark masses
to be ~ Mev and Mev.Comment: 15 pages, LATEX, 2 tables. (submitted to Phys.Rev.D
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