3,490 research outputs found
Branes with Background Fields in Boundary State Formalism
Interaction of branes in presence of internal gauge fields is considered by
using the boundary state formalism. This approach enables us to consider the
problems that are not easily accessible to the canonical approach via open
strings. The effects of compactification of some of the dimensions on tori are
also discussed. Also we study the massless state contribution on this
interaction.Comment: 12 pp. No figure
Heavy quark potential in the instanton liquid model
We study the heavy quark potential in the instanton liquid model by carefully
measuring Wilson loops out to a distance of order 3. A random instanton
ensemble with a fixed radius = 1/3 generates a potential
growing very slowly at large . In contrast, a more realistic size
distribution growing as at small and decaying as at
large , leads to a potential which grows linearly with . The string
tension, however, is only about 1/10 of the phenomenological value.Comment: LATTICE98(confine
Function generator eliminates necessity of series summation
Diode generator using four building-block circuits produces complex waveforms without the necessity of series summation. This highly specialized method of producing complex waveforms requires less power than present methods and uses simpler circuitry
Charged Black Holes in Two-Dimensional String Theory
We discuss two dimensional string theories containing gauge fields introduced
either via coupling to open strings, in which case we get a Born-Infeld type
action, or via heterotic compactification. The solutions to the modified
background field equations are charged black holes which exhibit interesting
space-time geometries. We also compute their masses and charges.Comment: 39 page
Gauge Fields and Space-Time
In this article I attempt to collect some ideas,opinions and formulae which
may be useful in solving the problem of gauge/ string / space-time
correspondence This includes the validity of D-brane representation, counting
of gauge-invariant words, relations between the null states and the Yang-Mills
equations and the discussion of the strong coupling limit of the string sigma
model. The article is based on the talk given at the "Odyssey 2001" conference.Comment: 20 page
Mixed Branes Interaction in Compact Spacetime
We present a general description of two mixed branes interactions. For this
we consider two mixed branes with dimensions p_1 and p_2, in external field
B_{\mu\nu} and arbitrary gauge fields A^1_{\alpha_1} and A^2_{\alpha_2} on the
world volume of them, in spacetime in which some of its directions are
compactified on circles with different radii. Some examples are considered to
clear these general interactions. Finally contribution of the massless states
on the interactions is extracted. Closed string with mixed boundary conditions
and boundary state formalism, provide useful tools for calculation of these
interactions.Comment: 22 pages, to appear in Nucl. Phys.
Anomaly induced effective actions in even dimensions and reliability of s-wave approximation
The reduction of 4d matter-gravity theory to , or leads to
effective 2d dilatonic gravity with dilaton coupled matter. Spinors give the
exceptional example of the theory which is conformally invariant in 4d as well
as in 2d, after reduction. We find 4d and 2d conformal anomaly induced
effective action (EA) for Majorana spinor. It is expected for some time that
s-wave EA (i.e. the one for dilaton coupled 2d matter) is some (s-wave)
approximation to 4d EA. We compare such 2d and 4d spinor EAs on the same
gravitational background and argue that s-wave EA indeed qualitatively
corresponds to no higher derivatives approximation for 4d EA.Comment: LaTeX file, 12 pages, the discussion of the Hawking radiation is
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Born-Infeld strings between D-branes
We examine the solutions of world-volume action for a D3-brane being put near
other D3-brane which is replaced by the background configuration of bulk space.
It is shown that the BPS solutions are not affected by the D3-brane background,
and they are interpreted as dyonic strings connecting two branes. On the
contrary, the non-BPS configurations are largely influenced by the background
D-brane, and we find that the solutions with pure electric charge cannot
connect two branes. These solutions are corresponding to the bound state of
brane and anti-brane which has been found by Callan and MaldacenaComment: 14 pages, 8 figure
S-Wave Scattering of Charged Fermions by a Magnetic Black Hole
We argue that, classically, -wave electrons incident on a magnetically
charged black hole are swallowed with probability one: the reflection
coefficient vanishes. However, quantum effects can lead to both electromagnetic
and gravitational backscattering. We show that, for the case of extremal,
magnetically charged, dilatonic black holes and a single flavor of low-energy
charged particles, this backscattering is described by a perturbatively
computable and unitary -matrix, and that the Hawking radiation in these
modes is suppressed near extremality. The interesting and much more difficult
case of several flavors is also discussed.Comment: 9p
Simulation study of intracity helicopter operations under instrument conditions to category 1 minimums
A fixed-base simulator study was conducted to define pilot workload and task performance associated with instrument flight operations for an intracity helicopter passenger service. Displays considered necessary to provide a minimal capability under Instrument Flight Rules conditions were used to fly a representative commercial helicopter route structure in the New York area, with each terminal assumed to be equipped with a precision approach guidance system. A cross section of pilots participated as test subjects, and despite the high workload level, the results indicated that for the assumptions employed, minimums of 61 m (200 ft) ceiling and 805 m (0.5 mile) visibility were feasible
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