570 research outputs found
Massive Superstrings are Black Holes
We argue that it is inconsistent to ignore the gravitational backreaction for
on-shell superstring states at the Planck mass and beyond, and that these
quantum states become Kerr black holes in the classical limit. Consequences are
discussed.Comment: 10 pages, IFP-708-UNC and VAND-TH-94-1
On the Greedy Algorithm for the Shortest Common Superstring Problem with Reversals
We study a variation of the classical Shortest Common Superstring (SCS)
problem in which a shortest superstring of a finite set of strings is
sought containing as a factor every string of or its reversal. We call this
problem Shortest Common Superstring with Reversals (SCS-R). This problem has
been introduced by Jiang et al., who designed a greedy-like algorithm with
length approximation ratio . In this paper, we show that a natural
adaptation of the classical greedy algorithm for SCS has (optimal) compression
ratio , i.e., the sum of the overlaps in the output string is at least
half the sum of the overlaps in an optimal solution. We also provide a
linear-time implementation of our algorithm.Comment: Published in Information Processing Letter
A Tissue P System and a DNA Microfluidic Device for Solving the Shortest Common Superstring Problem
This paper describes a tissue P system for solving the Shortest
Common Superstring Problem in linear time. This tissue P system is well
suited for parallel and distributed implementation using a micro°uidic device
working with DNA strands. The tP system is not based on the usual brute
force generate/test technique applied in DNA computing, but builds the space
solution gradually. The possible solutions/superstrings are build step by step
through the parallel distributed combination of strings using the overlapping
concatenation operation. Moreover, the DNA micro°uidic device solves the
problem autonomously, without the need of external control or manipulation
Heterotic M(atrix) Strings and Their Interactions
Following recent proposal of Dijkgraaf, Verlinde and Verlinde, we show that
the M(atrix) theory compactified on provides with a non-perturbative
description of second-quantized light-cone heterotic string. This so-called
heterotic M(atrix) string theory is defined by two-dimensional (8,0)
supersymmetric chiral gauge theory with gauge group SO(2N) in the large N
limit. We argue that at strong coupling fixed point the chiral gauge theory
flows to a (8,0) superconformal field theory defined via symmetric
product space orbifold. We show that the leading order correction to the strong
coupling expansion corresponds to a unique irrelevant operator of scaling
dimension three and describes joining and splitting cubic interactions of
light-cone heterotic string. We also speculate on M(atrix) description of
bosonic strings via dimensional reduction of d=26 Yang-Mills theory.Comment: 20 pages, section 3.1 expanded, more references adde
Seeking String Theory in the Cosmos
We review the existence, formation and properties of cosmic strings in string
theory, the wide variety of observational techniques that are being employed to
detect them, and the constraints that current observations impose on string
theory models.Comment: 25 pages; contribution for String Cosmology issue of Classical and
Quantum Gravity. References added and other improvements. Matches journal
versio
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