788 research outputs found
A Hidden Twelve-Dimensional SuperPoincare Symmetry In Eleven Dimensions
First, we review a result in our previous paper, of how a ten-dimensional
superparticle, taken off-shell, has a hidden eleven-dimensional superPoincare
symmetry. Then, we show that the physical sector is defined by three
first-class constraints which preserve the full eleven-dimensional symmetry.
Applying the same concepts to the eleven dimensional superparticle, taken
off-shell, we discover a hidden twelve dimensional superPoincare symmetry that
governs the theory.Comment: 13 page
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
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
Superstar in Noncommutative Superspace via Covariant Quantization of the Superparticle
A covariant quantization method is developed for the off-shell superparticle
in 10 dimensions. On-shell it is consistent with lightcone quantization, while
off-shell it gives a noncommutative superspace that realizes non-linearly a
hidden 11-dimensional super Poincare symmetry. The non-linear commutation rules
are then used to construct the supersymmetric generalization of the covariant
Moyal star product in noncommutative superspace. As one of the possible
applications, we propose this new product as the star product in supersymmetric
string field theory. Furthermore, the formalism introduces new techniques and
concepts in noncommutative (super)geometry.Comment: 17 pages, LaTe
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
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
Quantum Coherent String States in AdS_3 and SL(2,R) WZWN Model
In this paper we make the connection between semi-classical string
quantization and exact conformal field theory quantization of strings in 2+1
Anti de Sitter spacetime. More precisely, considering the WZWN model
corresponding to SL(2,R) and its covering group, we construct quantum {\it
coherent} string states, which generalize the ordinary coherent states of
quantum mechanics, and show that in the classical limit they correspond to
oscillating circular strings. After quantization, the spectrum is found to
consist of two parts: A continuous spectrum of low mass states (partly
tachyonic) fulfilling the standard spin-level condition necessary for unitarity
|j|< k/2, and a discrete spectrum of high mass states with asymptotic behaviour
m^2\alpha'\propto N^2 (N positive integer). The quantization condition for the
high mass states arises from the condition of finite positive norm of the
coherent string states, and the result agrees with our previous results
obtained using semi-classical quantization. In the k\to\infty limit, all the
usual properties of coherent or {\it quasi-classical} states are recovered. It
should be stressed that we consider the circular strings only for simplicity
and clarity, and that our construction can easily be used for other string
configurations too. We also compare our results with those obtained in the
recent preprint hep-th/0001053 by Maldacena and Ooguri.Comment: Misprints corrected. Final version to appear in Phys. Rev.
Метафора як когнітивний механізм номінації та її роль у мовній картині світу
Лексические единицы, образованные путем метафоризации, исследуются с
точки зрения когнитивной лингвистики как языковые репрезентации продуктов
концептуализации и категоризации социокультурной действительности сознанием человека. Объект исследования проанализирован в границах антропоцентричной парадигмы с применением компонентного, семантического и концептуального анализа.Важливим чинником актуальності дослідження є виявлення особливостей
лінгвокреативної діяльності людини, відображення її сучасного світобачення,
що проявляється у вербалізації та категоризації набутого нею досвіду і знань
про навколишню дійсність. Вивчення когнітивних механізмів номінації, а саме
процесів метафоризації з точки зору когнітивної лінгвістики, є актуальним аспектом вивчення мовного матеріалу. Застосований в роботі когнітивний підхід
до вивчення процесів метафоризації дозволив прослідкувати процес формування нового значення слова, встановити ті фрагменти знань і досвіду людини,
які отримали своє позначення в актах номінації за допомогою семантичної деривації.The semantic derivation is the main object of the article. The research of metaphor from the point of view of cognitive linguistics is actual in modern scientific linguistic
schools. The research focuses on cognitive mechanisms of new words coinage,
on their correlation with cognitive structures, on verbalization of relevant cognitive
structures. The emphasis is laid upon the metaphor as a cognitive mechanism of
nomination. The method of the conceptual analysis and componential analysis are
the major methods of the research
On the Possibility of a Trans-Planckian Duality
We investigate the possibility of a trans-Planckian duality, which exchanges
a manifold of events (space-time), with a manifold of momenta
(energy-momentum). Gravity has a dual counter-part, that is, a geometric theory
defined on the manifold of momenta. We provide a mathematical framework that
can possibly realize this idea, and analyze its classical behaviour.Comment: 21 pages, 4 figure
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