524,565 research outputs found

### String Theory

This is a rendering of a review talk on the state of String Theory, given at
the EPS-2003 Conference, intended for a wide audience of experimental and
theoretical physicists. It emphasizes general ideas rather than technical
aspects.Comment: 11 pages. Contribution to the EPS2003 conferenc

### A Universal w String Theory

It has been shown that there is a sequential embedding structure in a $w_N$\
string theory based on a linearized $W_N$\ algebra. The $w_N$\ string theory is
obtained as a special realization of the $w_{N+1}$\ string. The $w_{\infty}$\
string theory is a universal string theory in this sense. We have also shown
that there is a similar sequence for $N=1$\ string theory. The $N=1\ w_N$\
string can be given as a special case of the $N=1\ w_{N+1}$\ string. In
addition, we show that the $w_3$\ string theory is obtained as a special
realization of the $N=1\ w_3$\ string. We conjecture that the $w_N$\ string can
be obtained as a special $N=1\ w_N$\ string for general $w_N$. If this is the
case, $N=1\ w_{\infty}$\ string theory is more universal since it includes both
$N=0$\ and $N=1$\ $w_N$\ string theories.Comment: 19 pages, uses PHYZZX, typological errors corrected, OU-HET 18

### Gravitational Scattering Amplitudes and Closed String Field Theory in the Proper-Time Gauge

We construct a covariant closed string field theory by extending recent works
on the covariant open string field theory in the proper-time gauge. Rewriting
the string scattering amplitudes generated by the closed string field theory in
terms of the Polyakov string path integrals, we identify the Fock space
representations of the closed string vertices. We show that the Fock space
representations of the closed string field theory may be completely factorized
into those of the open string field theory. It implies that the well known
Kawai-Lewellen-Tye (KLT) relations of the first quantized string theory may be
promoted to the second quantized closed string theory. We explicitly calculate
the scattering amplitudes of three gravitons by using the closed string field
theory in the proper-time gauge.Comment: 5 pages, 1 figure, Talk given at 13th International Conference on
Gravitation, Astrophysics, and Cosmolog

### D-Branes, Tachyons, and String Field Theory

In these notes we provide a pedagogical introduction to the subject of
tachyon condensation in Witten's cubic bosonic open string field theory. We use
both the low-energy Yang-Mills description and the language of string field
theory to explain the problem of tachyon condensation on unstable D-branes. We
give a self-contained introduction to open string field theory using both
conformal field theory and overlap integrals. Our main subjects are the Sen
conjectures on tachyon condensation in open string field theory and the
evidence that supports these conjectures. We conclude with a discussion of
vacuum string field theory and projectors of the star-algebra of open string
fields. We comment on the possible role of string field theory in the
construction of a nonperturbative formulation of string theory that captures
all possible string backgrounds.Comment: 103 pages, 11 figures. Lectures presented at TASI 2001. v2:
references added. v3: minor errors corrected; reference, discussion added
regarding other results on open string spectrum in stable vacuu

### Nonrelativistic String Theory in Background Fields

Nonrelativistic string theory is a unitary, ultraviolet finite quantum
gravity theory with a nonrelativistic string spectrum. The vertex operators of
the worldsheet theory determine the spacetime geometry of nonrelativistic
string theory, known as the string Newton-Cartan geometry. We compute the Weyl
anomaly of the nonrelativistic string worldsheet sigma model describing strings
propagating in a string Newton-Cartan geometry, Kalb-Ramond and dilaton
background. We derive the equations of motion that dictate the backgrounds on
which nonrelativistic string theory can be consistently defined quantum
mechanically. The equations of motion we find from our study of the conformal
anomaly of the worldsheet theory are to nonrelativistic string theory what the
(super)gravity equations of motion are to relativistic string theory.Comment: 32 pages; v2: minor clarifications, fixed typos, references added;
v3: a reference adde

### String Interactions from Matrix String Theory

The Matrix String Theory, i.e. the two dimensional U(N) SYM with N=(8,8)
supersymmetry, has classical BPS solutions that interpolate between an initial
and a final string configuration via a bordered Riemann surface. The Matrix
String Theory amplitudes around such a classical BPS background, in the strong
Yang--Mills coupling, are therefore candidates to be interpreted in a stringy
way as the transition amplitude between given initial and final string
configurations. In this paper we calculate these amplitudes and show that the
leading contribution is proportional to the factor g_s^{-\chi}, where \chi is
the Euler characteristic of the interpolating Riemann surface and g_s is the
string coupling. This is the factor one expects from perturbative string
interaction theory.Comment: 15 pages, 2 eps figures, JHEP Latex class, misprints correcte

### Twist Field as Three String Interaction Vertex in Light Cone String Field Theory

It has been suggested that matrix string theory and light-cone string field
theory are closely related. In this paper, we investigate the relation between
the twist field, which represents string interactions in matrix string theory,
and the three-string interaction vertex in light-cone string field theory
carefully. We find that the three-string interaction vertex can reproduce some
of the most important OPEs satisfied by the twist field.Comment: 19 pages, 3 figures, LaTeX2e; v2: minor corrections, a reference
adde

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