203 research outputs found
Evolving fuzzy CP^n and lattice n-simplex
Generalizing the previous works on evolving fuzzy two-sphere, I discuss
evolving fuzzy CP^n by studying scalar field theory on it. The space-time
geometry is obtained in continuum limit, and is shown to saturate locally the
cosmic holographic principle. I also discuss evolving lattice n-simplex
obtained by `compactifying' fuzzy CP^n. It is argued that an evolving lattice
n-simplex does not approach a continuum space-time but decompactifies into an
evolving fuzzy CP^n.Comment: Typos corrected, 13 pages, no figures, LaTe
A Note on String Field Theory in the Temporal Gauge
In this note, we review the recent developments in the string field theory in
the temporal gauge. (Based on a talk presented by N.I. in the workshop {\it
Quantum Field Theory, Integrable Models and Beyond}, Yukawa Institute for
Theoretical Physics, Kyoto University, 14-18 February 1994.)Comment: 20 pages, KEK-TH-411, LaTex fil
Dualities of the entropy bound
I study the hypothetical thermodynamic system which saturates the so-called
Hubble entropy bound and show that it is invariant under the S- and T-dualities
of string theory as well as the interchanges of the eleventh dimension of
M-theory. I also discuss how unique the entropy bound is under the dualities
and some related issues.Comment: 7 pages, LaTeX, a reference replaced, minor correction
Field theory on evolving fuzzy two-sphere
I construct field theory on an evolving fuzzy two-sphere, which is based on
the idea of evolving non-commutative worlds of the previous paper. The
equations of motion are similar to the one that can be obtained by dropping the
time-derivative term of the equation derived some time ago by Banks, Peskin and
Susskind for pure-into-mixed-state evolutions. The equations do not contain an
explicit time, and therefore follow the spirit of the Wheeler-de Witt equation.
The basic properties of field theory such as action, gauge invariance and
charge and momentum conservation are studied. The continuum limit of the scalar
field theory shows that the background geometry of the corresponding continuum
theory is given by ds^2 = -dt^2+ t d Omega^2, which saturates locally the
cosmic holographic principle.Comment: Typos corrected, minor changes, 23 pages, no figures, LaTe
A Cooper pair light emitting diode
We demonstrate Cooper-pair's drastic enhancement effect on band-to-band
radiative recombination in a semiconductor. Electron Cooper pairs injected from
a superconducting electrode into an active layer by the proximity effect
recombine with holes injected from a p-type electrode and dramatically
accelerate the photon generation rates of a light emitting diode in the
optical-fiber communication band. Cooper pairs are the condensation of
electrons at a spin-singlet quantum state and this condensation leads to the
observed enhancement of the electric-dipole transitions. Our results indicate
the possibility to open up new interdisciplinary fields between
superconductivity and optoelectronics.Comment: 5 pages (4 figures
One-loop unitarity of scalar field theories on Poincare invariant commutative nonassociative spacetimes
We study scalar field theories on Poincare invariant commutative
nonassociative spacetimes. We compute the one-loop self-energy diagrams in the
ordinary path integral quantization scheme with Feynman's prescription, and
find that the Cutkosky rule is satisfied. This property is in contrast with
that of noncommutative field theory, since it is known that noncommutative
field theory with space/time noncommutativity violates unitarity in the above
standard scheme, and the quantization procedure will necessarily become
complicated to obtain a sensible Poincare invariant noncommutative field
theory. We point out a peculiar feature of the non-locality in our
nonassociative field theories, which may explain the property of the unitarity
distinct from noncommutative field theories. Thus commutative nonassociative
field theories seem to contain physically interesting field theories on
deformed spacetimes.Comment: 25 pages, 9 figures ; appendix and references adde
Self-consistency in Theories with a Minimal Length
The aim of this paper is to clarify the relation between three different
approaches of theories with a minimal length scale: A modification of the
Lorentz-group in the 'Deformed Special Relativity', theories with a
'Generalized Uncertainty Principle' and those with 'Modified Dispersion
Relations'. It is shown that the first two are equivalent, how they can be
translated into each other, and how the third can be obtained from them. An
adequate theory with a minimal length scale requires all three features to be
present.Comment: typos corrected, published with new title following referee's advic
Quantum field theory on a growing lattice
We construct the classical and canonically quantized theories of a massless
scalar field on a background lattice in which the number of points--and hence
the number of modes--may grow in time. To obtain a well-defined theory certain
restrictions must be imposed on the lattice. Growth-induced particle creation
is studied in a two-dimensional example. The results suggest that local mode
birth of this sort injects too much energy into the vacuum to be a viable model
of cosmological mode birth.Comment: 28 pages, 2 figures; v.2: added comments on defining energy, and
reference
Strings from position-dependent noncommutativity
We introduce a new set of noncommutative space-time commutation relations in
two space dimensions. The space-space commutation relations are deformations of
the standard flat noncommutative space-time relations taken here to have
position dependent structure constants. Some of the new variables are
non-Hermitian in the most natural choice. We construct their Hermitian
counterparts by means of a Dyson map, which also serves to introduce a new
metric operator. We propose PTlike symmetries, i.e.antilinear involutory maps,
respected by these deformations. We compute minimal lengths and momenta arising
in this space from generalized versions of Heisenberg's uncertainty relations
and find that any object in this two dimensional space is string like,
i.e.having a fundamental length in one direction beyond which a resolution is
impossible. Subsequently we formulate and partly solve some simple models in
these new variables, the free particle, its PT-symmetric deformations and the
harmonic oscillator.Comment: 11 pages, Late
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