arXiv subjects
Publications and source records attributed to Kamal L. Panigrahi.
We derive intersecting brane solutions in pp-wave spacetime by solving the supergravity field equations explicitly. The general intersection rules are presented. We also generalize the construction to the non-extremal solutions. Both the extremal and non-extremal solutions presented here are asymptotic to BFHP plane waves. We find that these solutions do not have regular horizons.
The light-like linear dilaton background presents a simple time dependent solution of type II supergravity equations of motion that preserves 1/2 supersymmetry in ten dimensions. We construct supergravity D-brane solutions in a linear dilaton background starting from the known intersecting brane solutions in string theory. By applying a Penrose limit on the intersecting (NS1-NS5-NS5')- brane solution, we find out a D5-brane in a linear dilaton background. We solve the Killing spinor equations for the brane solutions explicitly, and show that they preserve 1/4 supersymmetry. We also find a M5-brane solution in eleven dimensional supergravity.
We study aspects of Dirichlet S-branes, which are defined as Dirichlet boundary condition on a time like embedding of open strings, in general backgrounds. By applying T-duality along an isometry of the unphysical dS2-branes in NS-NS supported AdS3-background, we find S0-brane. We also study the time dependent tachyon condensation on the unstable Dp-brane and interpret the singular solutions as lower dimensional S(p-1)-brane that couples to real Ramond-Ramond fields while to imaginary NS-NS modes.
By using the Dirac-Born-Infeld action we study the dynamics of Dp-brane propagating in the NS5-near horizon plane wave background. We study systematically D-brane embedding in this pp-wave background, and analyze the equations of motion for various auxiliary fields. We further discuss the motion of the probe Dq-brane in the presence of source Dp-branes in this plane wave background.
We study the anti-de Sitter D-brane dynamics in Hamiltonian formulation. By exploiting the existence of certain conserved charges, we solve the equation of motion for a D1-brane in the AdS3 background and find the space-time dependent solutions. We further study the dynamics by mapping the problem to that of the open string tachyon, and examine the time dependent solutions in some detail.
We study D-branes in a two-dimensional Lorentzian orbifold R^{1,1}/Γwith a discrete boost Γ. This space is known as Misner or Milne space, and includes big crunch/big bang singularity. In this space, there are D0-branes in spiral orbits and D1-branes with or without flux on them. In particular, we observe imaginary parts of partition functions, and interpret them as the rates of open string pair creation for D0-branes and emission of winding closed strings for D1-branes. These phenomena occur due to the time-dependence of the background. Open string 2 -> 2 scattering amplitude on a D1-brane is also computed and found to be less singular than closed string case.
We study the homogeneous and time dependent dynamics of the supertube in diverse backgrounds. After deriving a general form of the Hamiltonian in general background, we use a particular gauge fixing, relevant to our analysis to derive a simpler Hamiltonian. We then study the homogeneous solutions of the equations of motion in various backgrounds and study the effective potential in detail.
We study D-branes in the Nappi-Witten model, which is a gauged WZW model based on (SL(2,R) x SU(2)) / (U(1) x U(1)). The model describes a four dimensional space-time consisting of cosmological regions with big bang/big crunch singularities and static regions with closed time-like curves. The aim of this paper is to investigate by D-brane probes whether there are pathologies associated with the cosmological singularities and the closed time-like curves. We first classify D-branes in a group theoretical way, and then examine DBI actions for effective theories on the D-branes. In particular, we show that D-brane metric from the DBI action does not include singularities, and wave functions on the D-branes are well behaved even in the presence of closed time-like curves.
We study rolling radion dynamics of electrified D-brane in NS5-brane background, both in effective field theory and in full open string theory. We construct exact boundary states and, from them, extract conserved Noether currents. We argue that T-duality and Lorentz boost offer an intuitive approach. In the limit of large number of NS5-branes, both boundary wave functions and conserved currents are sharply peaked and agree with those deduced from the effective field theory. As the number of NS5-branes is reduced, width around the peak becomes wider by string corrections. We also study radiative decay process. By applying Lorentz covariance, we show how the decay of electrified D-brane is related to that of bare D-brane. We compute spectral moments of final state energy and winding quantum number. Using Lorentz covariance argument, we explain in elementary way why winding quantum number should be included and derive rules how to do so. We conclude that Kutasov's "geometric realization" between radion rolling dynamics and tachyon rolling dynamics holds universally, both for bare and electrified D-branes.
By using Dirac-Born-Infeld action we study the real time dynamics of D-branes in the vicinity of a stack of Dp-branes where the role of the tachyon of the open string models is played by the radial mode on the D-branes. We examine the behaviour of the tachyon potential and study the hamiltonian formulation and classical solutions of such systems. We also study the homogeneous solutions of the classical equations of motion in these cases.
We present two classes of brane solutions in pp-wave spacetime. The first class of branes with a rotation parameter are constructed in an exact string background with NS-NS and R-R flux. The spacetime supersymmetry is analyzed by solving the standard Killing spinor equations and is shown to preserve the same amount of supersymmetry as the case without the rotation. This class of branes do not admit regular horizon. The second class of brane solutions are constructed by applying a null Melvin twist to the brane solutions of flat spacetime supergravity. These solutions admit regular horizon. We also comment on some thermodynamic properties of this class of solutions.
A class of Dp and Dp-D(p+4)-brane solutions are constructed in the Penrose limit of the linear-dilaton geometry. The classical solutions are shown to break all space-time supersymmetries. In the worldsheet description, the branes preserve as many supersymmetries as D-branes in flat space. It is shown that these supersymmetries do not have zero modes on the worldsheet and hence do not admit local space-time realizations. This indicates that, unlike the perturbative spectrum, the D-brane spectrum of strings in the linear-dilaton pp-wave is not similar to the flat space case.
We present classical solutions of Dp-branes $(p \ge 5)$ in plane wave spacetime with nonconstant R-R 3-form flux. We also show the existence of a system of D3-branes in this background. We further analyze the supersymmetric properties of these branes by solving type II Killing spinor equations explicitly.
We find classical solutions of D-branes in pp-wave spacetime with nonconstant NS-NS flux. We also present Dp-Dp' bound state solutions in this background. We further analyze the supersymmetric properties of these brane solutions by solving the type IIB killing spinor equations explicitly.
We present several supergravity solutions corresponding to both Dp, as well as Dp-Dp' systems, in NS-NS and R-R PP-wave background originating from AdS_3 times S^3 times R^4. The Dp brane solutions, p=1,..,5 are fully localized, whereas Dp-Dp' are localized along common transverse directions. We also discuss the supersymmetry properties of these solutions and the worldsheet construction for the p-p' system.
We construct new D-brane bound states using charged macroscopic type IIB string solutions.A generic bound state solution, when dimensionally reduced, carries multiple gauge charges. Starting with D=9 charged macroscopic strings, we obtain solutions in D=10, which are interpreted as carrying (F, D0, D2) charges as well as nonzero momenta. The masses and charges are also explicitly shown to satisfy the non-threshold bound of 1/2 BPS objects. Our solutions reduce to the known D-brane bound state solutions with appropriate restrictions in the parameter space. We further generalize the results to (Dp- D(p+2)) bound state in IIA/B theories, giving an explicit example with p=1.