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56
Recent Developments in Superstring Theory
, 2000
"... The talk contains a brief introduction string theory, followed by a discussion of some of the recent developments. This talk will begin with a brief review of pre1994 string theory. Then I shall describe the develoments during 19941996 which include duality symmetries, Dbranes and black holes. Fi ..."
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The talk contains a brief introduction string theory, followed by a discussion of some of the recent developments. This talk will begin with a brief review of pre1994 string theory. Then I shall describe the develoments during 19941996 which include duality symmetries, Dbranes and black holes. Finally I shall turn to the discussion of some of the developments during 19972000. The topics covered will include (M)atrix theory, Maldacena conjecture, noncommutative geometry, tachyon condensation, special limits of string theory in which gravity decouples (little string theories, OM theory etc.) and large radius compactification. This however is not an exhaustive review of string theory. Indeed, many of the important developments in this subject, like mirror symmetry, new ideas about cosmological constant, etc. will be left out of this review. I shall work in the convention ¯h = 1, c = 1.
Note on DBI dynamics of Dbrane near NS5branes,” Phys
 Rev. D
"... In this note, we investigate the homogeneous radial dynamics of (Dp, NS5)systems without and with one compactified transverse direction, in the framework of DBI effective action. During the homogeneous evolution, the electric field on the Dbrane is always conserved and the radial motion could be r ..."
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In this note, we investigate the homogeneous radial dynamics of (Dp, NS5)systems without and with one compactified transverse direction, in the framework of DBI effective action. During the homogeneous evolution, the electric field on the Dbrane is always conserved and the radial motion could be reduced to an onedimension dynamical system with an effective potential. When the Dpbrane energy is not high, the brane moves in a restricted region, with the orbits depending on the conserved energy, angular momentum through the form of the effective potential. When the Dpbrane energy is high enough, it can escape to the infinity. Moreover, the conserved angular momentum plays an interesting role in the dynamics.
Matrix Model, Noncommutative Gauge Theory and the Tachyon Potential
, 2000
"... We describe the D2 braneantiD2brane system in the framework of BFSS Matrix model and noncommutative gauge theory. We find the physical spectrum of fields by appropriate gauge fixing and compute the exact tachyon potential. We provide an exact description of tachyon condensation in terms of physica ..."
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We describe the D2 braneantiD2brane system in the framework of BFSS Matrix model and noncommutative gauge theory. We find the physical spectrum of fields by appropriate gauge fixing and compute the exact tachyon potential. We provide an exact description of tachyon condensation in terms of physical variables of the NC gauge theory. We exhibit multiple vortex production with increasing topological charge and interpret this as gradual conversion of the braneantibrane system to D0 branes. The entire analysis is carried out using the known hamiltonian of the Matrix model, which is equivalent to the hamiltonian of the NC gauge theory. We identify the supersymmetric ground state of this hamiltonian with the tachyonic vacuum; Sen’s conjecture about the latter follows simply from this identification. We also find two types of closed string excitations, solitonic as well as
Quantum corrections in padic string theory,” arXiv:hepth/0105312
 19 M. Gutperle and A. Strominger, “Spacelike branes,” JHEP
, 2002
"... We compute loop corrections in padic open string field theory. We argue that quantum effects induce a pole with m 2 ∼ − ln g for the open string field at the locally stable vacuum. We also compute the one loop effective potential and show that the potential develops an imaginary piece when the fie ..."
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We compute loop corrections in padic open string field theory. We argue that quantum effects induce a pole with m 2 ∼ − ln g for the open string field at the locally stable vacuum. We also compute the one loop effective potential and show that the potential develops an imaginary piece when the field becomes tachyonic. 1
Branes Ending On Branes In A Tachyon Model
, 2001
"... In a tachyon model proposed by Minahan and Zwiebach, we construct various new solutions which correspond to nontrivial brane configurations in string theory. Our solutions include DpD(p−2) bound states, (F, Dp) bound states, string junctions, D(p−2)branes ending on a Dpbrane, D(p−2)branes suspen ..."
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In a tachyon model proposed by Minahan and Zwiebach, we construct various new solutions which correspond to nontrivial brane configurations in string theory. Our solutions include DpD(p−2) bound states, (F, Dp) bound states, string junctions, D(p−2)branes ending on a Dpbrane, D(p−2)branes suspended between parallel Dpbranes and their noncommutative generalizations. We find the Bogomol’nyi bounds and the BPS equations for some of our solutions, and check the physical consistency of our solutions with the Dbrane picture by looking at the distributions of their energies and RRcharges in space. We also give conjectures for a few other brane configurations.
2001 Pulse propagation in Born–Infeld theory, the world volume equivalence principle and the equation of state of the Chaplygin gas Preprint hepth/0104015
"... A recently proposed worldvolume equivalence principal involving the Boillat, as opposed to the Einstein, metric is examined in the context of some colliding wave solutions of the BornInfeld equations for which two plane polarized pulses pass through one another without distortion. They suffer a de ..."
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A recently proposed worldvolume equivalence principal involving the Boillat, as opposed to the Einstein, metric is examined in the context of some colliding wave solutions of the BornInfeld equations for which two plane polarized pulses pass through one another without distortion. They suffer a delay with respect to the usual Einstein metric but not with respect to the Boillat metric. Both metrics are flat in this case, and the closed string and open string causal structures are interchanged by the Legendre transformation that is used for solving the associated MongeAmpère equation. In 1+1 dimensions the equations are known to be equivalent to the vorticity free motion of a Chaplygin gas. The latter is shown to be described by the scalar BornInfeld equation in all dimensions and it is pointed out that the equation of state is Hagedornlike: there is an upper bound to the pressure and temperature. 1
Komaba Lectures on
, 2001
"... These lectures provide an introduction to noncommutative geometry and its origins in quantum mechanics and to the construction of solitons in noncommutative field theory. These ideas are applied to the construction of Dbranes as solitons of the tachyon field in noncommutative open string theory. A ..."
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These lectures provide an introduction to noncommutative geometry and its origins in quantum mechanics and to the construction of solitons in noncommutative field theory. These ideas are applied to the construction of Dbranes as solitons of the tachyon field in noncommutative open string theory. A brief discussion is given of the Ktheory classification
Interpolating between open and closed strings  a BSFT approach,” [arXiv:hepth/0203185
"... We address the conjecture that at the tachyonic vacuum open strings get transformed into closed strings. We show that it is possible in the context of boundary string field theory to interpolate between the conventional open string theory, characterized by having the D25 brane as the boundary state, ..."
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We address the conjecture that at the tachyonic vacuum open strings get transformed into closed strings. We show that it is possible in the context of boundary string field theory to interpolate between the conventional open string theory, characterized by having the D25 brane as the boundary state, and an offshell (open) string theory where the boundary state is identified with the closed string vacuum, where holomorphic and antiholomorphic modes decouple and where bulk vertex operator correlation functions are identical to those of the closed string. 1
Strings as Flux Tube and Deconfinement on Branes in Gauge Theories
, 2001
"... We propose gauge theories in which the unstable branes and the fundamental string are realized as classical solutions. While the former are represented by domain wall like configurations of a scalar field coupled to the gauge field, the latter is by a confined flux tube in the bulk. It is shown that ..."
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We propose gauge theories in which the unstable branes and the fundamental string are realized as classical solutions. While the former are represented by domain wall like configurations of a scalar field coupled to the gauge field, the latter is by a confined flux tube in the bulk. It is shown that the confined flux tube is really a source of the bulk Bfield. Our model also provides a natural scenario of the confinement on the brane in the context of the open string tachyon condensation. It is also argued that the fundamental string can be realized as a classical solution in a certain IIB matrix model as in our model.