1,207 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
Conformal Symmetry and Duality between Free Particle, H-atom and Harmonic Oscillator
We establish a duality between the free massless relativistic particle in d
dimensions, the non-relativistic hydrogen atom (1/r potential) in (d-1) space
dimensions, and the harmonic oscillator in (d-2) space dimensions with its mass
given as the lightcone momentum of an additional dimension. The duality is in
the sense that the classical action of these systems are gauge fixed forms of
the same worldline gauge theory action at the classical level, and they are all
described by the same unitary representation of the conformal group SO(d,2) at
the quantum level. The worldline action has a gauge symmetry Sp(2) which treats
canonical variables (x,p) as doublets and exists only with a target spacetime
that has d spacelike dimensions and two timelike dimensions. This spacetime is
constrained due to the gauge symmetry, and the various dual solutions
correspond to solutions of the constraints with different topologies. For
example, for the H-atom the two timelike dimensions X^{0'},X^{0} live on a
circle. The model provides an example of how realistic physics can be viewed as
existing in a larger covariant space that includes two timelike coordinates,
and how the covariance in the larger space unifies different looking physics
into a single system.Comment: Latex, 23 pages, minor improvements. In v3 a better gauge choice for
u for the H-atom is made; the results are the sam
Supersymmetric Two-Time Physics
We construct an Sp(2,R) gauge invariant particle action which possesses
manifest space-time SO(d,2) symmetry, global supersymmetry and kappa
supersymmetry. The global and local supersymmetries are non-abelian
generalizations of Poincare type supersymmetries and are consistent with the
presence of two timelike dimensions. In particular, this action provides a
unified and explicit superparticle representation of the superconformal groups
OSp(N/4), SU(2,2/N) and OSp(8*/N) which underlie various AdS/CFT dualities in
M/string theory. By making diverse Sp(2,R) gauge choices our action reduces to
diverse one-time physics systems, one of which is the ordinary (one-time)
massless superparticle with superconformal symmetry that we discuss explicitly.
We show how to generalize our approach to the case of superalgebras, such as
OSp(1/32), which do not have direct space-time interpretations in terms of only
zero branes, but may be realizable in the presence of p-branes.Comment: Latex, 18 page
Exact Effective Action and Spacetime Geometry in Gauged WZW Models
We present an effective quantum action for the gauged WZW model
. It is conjectured that it is valid to all orders of the
central extension on the basis that it reproduces the exact spacetime
geometry of the zero modes that was previously derived in the algebraic
Hamiltonian formalism. Besides the metric and dilaton, the new results that
follow from this approach include the exact axion field and the solution of the
geodesics in the exact geometry. It is found that the axion field is generally
non-zero at higher orders of even if it vanishes at large . We work
out the details in two specific coset models, one non-abelian, i.e.
and one abelian, i.e SL(2,\IR)\otimes
SO(1,1)^{d-2}/SO(1,1). The simplest case SL(2,\IR)/\IR corresponds to a
limit.Comment: 20 pages, harvmac, USC-93/HEP-B1, (The exact general expression for
the dilaton is added in Sec.5
Examples of D=11 S-supersymmetric actions for point-like dynamical systems
A non standard super extensions of the Poincare algebra (S-algebra [1,2]),
which seems to be relevant for construction of various D=11 models, are
studied. We present two examples of actions for point-like dynamical systems,
which are invariant under off-shell closed realization of the S-algebra as well
as under local fermionic -symmetry. On this ground, an explicit form of
the S-algebra is advocated.Comment: 18 pages, LaTex fil
Conformally Exact Metric and Dilaton in String Theory on Curved Spacetime
Using a Hamiltonian approach to gauged WZW models, we present a general
method for computing the conformally exact metric and dilaton, to all orders in
the expansion, for any bosonic, heterotic, or type-II superstring model
based on a coset . We prove the following relations: (i) For type-II
superstrings the conformally exact metric and dilaton are identical to those of
the non-supersymmetric {\it semi-classical} bosonic model except for an overall
renormalization of the metric obtained by . (ii) The exact
expressions for the heterotic superstring are derived from their exact bosonic
string counterparts by shifting the central extension (but an
overall factor remains unshifted). (iii) The combination
is independent of and therefore can be computed in lowest
order perturbation theory as required by the correct formulation of a
conformally invariant path integral measure. The general formalism is applied
to the coset models that are relevant for
string theory on curved spacetime. Explicit expressions for the conformally
exact metric and dilaton for the cases are given. In the
semiclassical limit our results agree with those obtained with
the Lagrangian method up to 1-loop in perturbation theory.Comment: USC-92/HEP-B2, 19 pages and 3 figure
Green-Schwarz type formulation of D=11 S - invariant superstring and superparticle actions
A manifestly Poincare invariant formulations for and SO(2,9)
superstring actions are proposed. The actions are invariant under a local
fermionic -symmetry as well as under a number of global symmetries,
which turn out to be on-shell realization of the known ``new supersymmetry``
S-algebra. Canonical quantization of the theory is performed and relation of
the quantum state spectrum with that of type IIA Green-Schwarz superstring is
discussed. Besides, a mechanical model is constructed, which is a zero tension
limit of the D=11 superstring and which incorporates all essential features of
the latter. A corresponding action invariant under off-shell closed realization
of the S-algebra is obtained.Comment: Revised version, in particular, discussion of SO(2,9) case is
included. To be published in Int. J. Mod. Phys.
Modified Kantowski-Sachs Cosmologies from Coset Models
We show how different modifications of Kantowski-Sachs cosmologies emerge in
four dimensions as dimensional reduction of the gauged Wess-Zumino-Witten model
based on .Comment: 7 pages, Latex, no figure
Hamiltonian Noether theorem for gauge systems and two time physics
The Noether theorem for Hamiltonian constrained systems is revisited. In
particular, our review presents a novel method to show that the gauge
transformations are generated by the conserved quantities associated with the
first class constraints. We apply our results to the relativistic point
particle, to the Friedberg et al. model and, with special emphasis, to two time
physics.Comment: 20 pages, Latex, references added, the "massless" sense of (87) is
clarifie
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