35 research outputs found
Rolling down to D-brane and tachyon matter
We investigate the spatially inhomogeneous decay of an unstable D-brane and
construct an asymptotic solution which describes a codimension one D-brane and
the tachyon matter in boundary string field theory. In this solution, the
tachyon matter exists around the lower-dimensional D-brane.Comment: 8 pages, references added, solution corrected, revised and extended
version, v4:published versio
Aspects of Tachyonic Inflation with Exponential Potential
We consider issues related to tachyonic inflation with exponential potential.
We find exact solution of evolution equations in the slow roll limit in FRW
cosmology. We also carry out similar analysis in case of Brane assisted
tachyonic inflation. We investigate the phase space behavior of the system and
show that the dust like solution is a late time attractor. The difficulties
associated with reheating in the tachyonic model are also indicated.Comment: New References added. To appear in Phys. Rev.
On open superstring partition function in inhomogeneous rolling tachyon background
We consider open superstring partition function Z on the disc in
time-dependent tachyon background T= f(x_i) e^{m x_0} where the profile
function f depends on spatial coordinates. We compute Z to second order in
derivatives of f and compare the result with some previously suggested
effective actions depending only on the first derivatives of the tachyon field.
We also compute the target-space stress-energy tensor in this background and
demonstrate its conservation in the ``on-shell'' case of the linear profile f=
f_0 + q_i x_i corresponding to a marginal perturbation. We comment on the role
of the rolling tachyon with linear spatial profile in the decay of an unstable
D-brane.Comment: 32p, latex, v2: introduction revised to expand and correct comments
on the paper by Kutasov and Niarchos, v3: corrected typos and formulas in
section 4, final version to appear in JHE
Electromagnetic String Fluid in Rolling Tachyon
We study Born-Infeld type effective action for unstable D3-brane system
including a tachyon and an Abelian gauge field, and find the rolling tachyon
with constant electric and magnetic fields as the most general homogeneous
solution. Tachyonic vacua are characterized by magnitudes of the electric and
magnetic fields and the angle between them. Analysis of small fluctuations in
this background shows that the obtained configuration may be interpreted as a
fluid consisting of string-like objects carrying electric and magnetic fields.
They are stretched along one direction and the rolling tachyon move in a
perpendicular direction to the strings. Direction of the propagating waves
coincides with that of strings with velocity equal to electric field.Comment: LaTeX, 18 pages, 1 figure, minor correction
Inflationary Attractor from Tachyonic Matter
We study the complete evolution of a flat and homogeneous universe dominated
by tachyonic matter. We demonstrate the attractor behaviour of the tachyonic
inflation using the Hamilton-Jacobi formalism. We else obtain analytical
approximations to the trajectories of the tachyon field in different regions.
The numerical calculation shows that an initial non-vanishing momentum does not
prevent the onset of inflation. The slow-rolling solution is an attractor.Comment: 4 pages, 2 figures, RevTe
Caustic Formation in Tachyon Effective Field Theories
Certain configurations of D-branes, for example wrong dimensional branes or
the brane-antibrane system, are unstable to decay. This instability is
described by the appearance of a tachyonic mode in the spectrum of open strings
ending on the brane(s). The decay of these unstable systems is described by the
rolling of the tachyon field from the unstable maximum to the minimum of its
potential. We analytically study the dynamics of the inhomogeneous tachyon
field as it rolls towards the true vacuum of the theory in the context of
several different tachyon effective actions. We find that the vacuum dynamics
of these theories is remarkably similar and in particular we show that in all
cases the tachyon field forms caustics where second and higher derivatives of
the field blow up. The formation of caustics signals a pathology in the
evolution since each of the effective actions considered is not reliable in the
vicinity of a caustic. We speculate that the formation of caustics is an
artifact of truncating the tachyon action, which should contain all orders of
derivatives acting on the field, to a finite number of derivatives. Finally, we
consider inhomogeneous solutions in p-adic string theory, a toy model of the
bosonic tachyon which contains derivatives of all orders acting on the field.
For a large class of initial conditions we conclusively show that the evolution
is well behaved in this case. It is unclear if these caustics are a genuine
prediction of string theory or not.Comment: 23 pages, 5 figures; accepted for publication in JHEP. Revised
derivation of eikonal equation for the DBI action. Added comments concerning
the relationship between p-adic string theory and tachyon matter. Added
second example of inhomogeneous evolution in p-adic string theory. Misleading
statements concerning caustic-free evolution removed, references adde
Tachyon Kinks on Unstable Dp-branes
In the context of tachyon effective theory coupled to Born-Infeld
electromagnetic fields, we obtain all possible singularity-free static flat
configurations of codimension one on unstable Dp-branes. Computed tension and
string charge density suggest that the obtained kinks are D(p-1) or
D(p-1)F1-branes.Comment: 22pages, LaTeX2e, 7figure
Decay of Unstable D-branes with Electric Field
Using the techniques of two dimensional conformal field theory we construct
time dependent classical solutions in open string theory describing the decay
of an unstable D-brane in the presence of background electric field, and
explicitly evaluate the time dependence of the energy momentum tensor and the
fundamental string charge density associated with this solution. The final
decay product can be interpreted as a combination of stretched fundamental
strings and tachyon matter.Comment: 35 pages, LaTe
Survival probability of mutually killing Brownian motions and the O'Connell process
Recently O'Connell introduced an interacting diffusive particle system in
order to study a directed polymer model in 1+1 dimensions. The infinitesimal
generator of the process is a harmonic transform of the quantum Toda-lattice
Hamiltonian by the Whittaker function. As a physical interpretation of this
construction, we show that the O'Connell process without drift is realized as a
system of mutually killing Brownian motions conditioned that all particles
survive forever. When the characteristic length of interaction killing other
particles goes to zero, the process is reduced to the noncolliding Brownian
motion (the Dyson model).Comment: v2: AMS-LaTeX, 20 pages, 2 figures, minor corrections made for
publication in J. Stat. Phy