U-duality p-branes in toroidally compactified type II superstring theories in space-time dimensio... more U-duality p-branes in toroidally compactified type II superstring theories in space-time dimensions 10> D ≥ 4 can be constructed explicitly based on the conjectured U-duality symmetries and the corresponding known single-charge super p-brane configurations. As concrete examples, we first construct explicitly the SL(3,Z) superstrings and SL(3,Z) × SL(2,Z) 0-branes as well as their corresponding magnetic duals in D = 8. For the SL(3,Z) superstrings (3-branes), each of them is characterized by a triplet of integers corresponding to the electric-like (magneticlike) charges associated with the three 2-form gauge potentials present in the theory. For the SL(3,Z) × SL(2,Z) 0-branes (4-branes), each of them is labelled by a pair of triplets of integers corresponding to the electric-like (magnetic-like) charges associated with the two sets of three 1-form gauge potentials. The string (3-brane) tension and central charge are shown to be given by SL(3,Z) invariant expressions. It is argued ...
We show directly in the Lax operator approach how the Virasoro and W-constraints on the τ-functio... more We show directly in the Lax operator approach how the Virasoro and W-constraints on the τ-function arise in the p-reduced KP hierarchy or Generalized KdV hierarchy. In particular, we consider the KdV and the Boussinesq hierarchy to show that the Virasoro and the W-constraints follow from the string equation by expanding the “additional symmetry” operator in terms of the Lax operator. We also mention how this method could be generalized for higher KdV hierarchies. (∗) Address after 1st November 1992: Institute for Theoretical Physics, Groningen University,
It is known from the work in [1] of Lu et. al. that the non-supersymmetric charged D3-brane (with... more It is known from the work in [1] of Lu et. al. that the non-supersymmetric charged D3-brane (with anisotropies in time as well as one of the spatial directions of D3-brane) of type IIB string theory is characterized by five independent parameters. By fixing one of the parameters and zooming into a particular region of space-time we construct a four parameter family of solution in AdS5, which interpolates between AdS5 black hole and AdS5 soliton (when one of spatial directions in the Poincare coordinates is compact) by continuously changing the parameters (there is no need to take a double Wick rotation as is usual to go from one solution to the other) from one set of values to another. We consider two cases. In the first case the dilaton is constant for this transition and there are only three independent parameters, whereas in the second case the dilaton varies and there are four independent parameters. In the latter case, the solution interpolates between AdS5 black hole, AdS5 sol...
We construct a four dimensional de Sitter space upto a conformal transformation by compactifying ... more We construct a four dimensional de Sitter space upto a conformal transformation by compactifying the anisotropic SD3-brane solution of type IIB string theory on a six dimensional product space of the form H_5 × S^1, where H_5 is a five dimensional hyperbolic space and S^1 is a circle. The radius of the hyperbolic space is chosen to be constant. The radius of the circle and the dilaton in four dimensions are time dependent and not constant in general. By different choices of parameters characterizing the SD3-brane solution either the dilaton or the radius of the circle can be made constant but not both. The form-field is also non-vanishing in general, but it can be made to vanish without affecting the solution. This construction might be useful for a better understanding of dS/CFT correspondence as well as for cosmology.
We construct the intersecting non-supersymmetric (non-susy) D1/D5 solution of type IIB string the... more We construct the intersecting non-supersymmetric (non-susy) D1/D5 solution of type IIB string theory. While, as usual, the solution is charged under an electric two-form and an electric six-form gauge field, it also contains a non-susy chargeless (non-BPS) D0-brane. The S-dual of this solution is the non-susy F/NS5 solution. We show how these solutions nicely interpolate between the corresponding black (or non-extremal) solutions and the Kaluza-Klein (KK) "bubble of nothing" (BON) by continuously changing some parameters characterizing the solutions from one set of values to another. We show, by a time symmetric general bubble initial data analysis, that the final bubbles in these cases are static and stable and the interpolations can be physically interpreted as closed string tachyon condensation. As special cases, we recover the transition of two charge black F-string to BON, considered by Horowitz, and also the transition from AdS_3 black hole to global AdS_3.
In a previous work, we have shown that, like BPS Dp branes, bulk gravity gets decoupled from the ... more In a previous work, we have shown that, like BPS Dp branes, bulk gravity gets decoupled from the brane even for the non-susy Dp branes of type II string theories indicating a possible extension of AdS/CFT correspondence for the non-supersymmetric case. In that work, the decoupling of gravity on the non-susy Dp branes has been shown numerically for the general case as well as analytically for some special case. Here we discuss the decoupling limit and the throat geometry of the non-susy D3 brane when the charge associated with the brane is very large. We show that in the decoupling limit the throat geometry of the non-susy D3 brane, under appropriate coordinate change, reduces to the Constable-Myers solution and thus confirming that this solution is indeed the holographic dual of a (non-gravitational) gauge theory discussed there. We also show that when one of the parameters of the solution takes a specific value, it reduces, under another coordinate change, to the five-dimensional s...
We show that the (M5, M2, M2', MW) bound state solution of eleven dimensional supergravity re... more We show that the (M5, M2, M2', MW) bound state solution of eleven dimensional supergravity recently constructed in hep-th/0009147 is related to the (M5, M2) bound state one by a finite Lorentz boost along a M5-brane direction perpendicular to the M2-brane. Given the (M5, M2) bound state as a defining system for OM theory and the above relation between this system and the (M5, M2, M2', MW) bound state, we test the recently proposed V-duality conjecture in OM theory. Insisting to have a decoupled OM theory, we find that the allowed Lorentz boost has to be infinitesimally small, therefore resulting in a family of OM theories related by Galilean boosts. We argue that such related OM theories are equivalent to each other. In other words, V-duality holds for OM theory as well. Upon compactification on either an electric or a `magnetic' circle (plus T-dualities as well), the V-duality for OM theory gives the known one for either noncommutative open string theories or noncommuta...
We consider the space-like Dp brane solutions of type II string theories having isometries ISO(p+... more We consider the space-like Dp brane solutions of type II string theories having isometries ISO(p+1) × SO(8-p,1). These are asymptotically flat solutions or in other words, the metrics become flat at the time scale τ≫τ_0. On the other hand, when τ∼τ_0, we get (p+1)+1 dimensional flat FLRWmetrics upon compactification on a (8-p) dimensional hyperbolic space with time dependent radii. We show that the resultant (p+1)+1 dimensional metrics describe transient accelerating cosmologies for all p from 1 to 6, i.e., from (2+1) to (7+1) space-time dimensions. We show how the acceleration changes with the interplay of the various parameters characterizing the solutions in (3+1) dimensions. Finally, for τ≪τ_0, after compactification on (8-p) dimensional hyperbolic space, the resultant metrics are shown to take the form of (p+1)+1 dimensional de Sitter spaces upto a conformal transformation. Cosmologies here are decelerating, but, only in a particular conformal frame we get eternal acceleration.
This is a companion paper of our previous work [1] where we studied the thermodynamics and phase ... more This is a companion paper of our previous work [1] where we studied the thermodynamics and phase structure of asymptotically flat black p-branes in a cavity in arbitrary dimensions D in a canonical ensemble. In this work we study the thermodynamics and phase structure of the same in a grand canonical ensemble. Since the boundary data in two cases are different (for the grand canonical ensemble boundary potential is fixed instead of the charge as in canonical ensemble) the stability analysis and the phase structure in the two cases are quite different. In particular, we find that there exists an analog of one-variable analysis as in canonical ensemble, which gives the same stability condition as the rather complicated known (but generalized from black holes to the present case) two-variable analysis. When certain condition for the fixed potential is satisfied, the phase structure of charged black p-branes is in some sense similar to that of the zero charge black p-branes in canonical...
We compute the expectation values of both the time-like and the light-like Wilson loops in a stro... more We compute the expectation values of both the time-like and the light-like Wilson loops in a strongly coupled plasma of (p+1)-dimensional Yang-Mills theories using gravity/gauge theory correspondence. From the time-like Wilson loop we obtain the velocity dependent quark-antiquark potential where the dipole is moving through the plasma with an arbitrary velocity 0<v<1 and also obtain expressions for the screening lengths. When the velocity v--> 1, the Wilson loop becomes light-like and we obtain the form of the jet quenching parameter in those strongly coupled plasma.
It was shown in Dey and Roy (2012) that the near horizon limit of the 1/4 BPS threshold F-Dp (for... more It was shown in Dey and Roy (2012) that the near horizon limit of the 1/4 BPS threshold F-Dp (for 0≤ p ≤ 5, p ≠ 4) bound state solutions of type II string theories give rise to space-time metrics endowed with Lifshitz scaling along with hyperscaling violation. Here we compute the holographic entanglement entropy of this system for all p ≠ 4 (for p=4 the space-time has AdS_2 structure). For p=3,5, we get the expected area law behavior of the entanglement entropy. For p=0,1, the entanglement entropy has new area law violations and has the behavior which is in between the linear and logarithmic behaviors. For p=2, we get a logarithmic violation of the area law. We also compute the entanglement entropy at finite temperature and show that as the temperature rises, the entanglement entropy makes a crossover to the thermal entropy of the system. We thus obtain the string theoretic realization of holographic EE and various of its aspects noted earlier for generic metric with hyperscaling vi...
It is found that a necessary completion of phase structure of D-dimensional charged black p-brane... more It is found that a necessary completion of phase structure of D-dimensional charged black p-brane (p > 0) in a cavity requires two additional thermodynamical phases, the so-called "bubble of nothing" and/or the extremal brane, in canonical ensemble. This finding resolves the puzzle about the missing phases which are needed for the underlying phase diagram when d̃ = D - p - 3 ≤ 2 and gives a new (bubble) phase which can become globally stable when d̃ > 2. An analog of Hawking-Page transition is also found among other new phase transitions, giving a complete phase structure in this setup.
By using the non-supersymmetric p-brane solutions delocalized in arbitrary number of transverse d... more By using the non-supersymmetric p-brane solutions delocalized in arbitrary number of transverse directions in type II supergravities, we show how they can be regarded as interpolating solutions between unstable Dp-branes (a non-BPS D-brane or a pair of coincident D-brane-antiD-brane) and fundamental strings and also between unstable Dp-branes and NS5-branes. We also show that some of these solutions can be regarded as interpolating solutions between NS5/N̅S̅5 and Dp-branes (for p ≤ 5). This gives a closed string description of the tachyon condensation and lends support to the conjecture that the open string theory on unstable D-branes at the tachyonic vacuum has soliton solutions describing not only the lower dimensional BPS D-branes, but also the fundamental strings as well as the NS5-branes.
By directly solving the equations of motion we obtain the time dependent solutions of supergravit... more By directly solving the equations of motion we obtain the time dependent solutions of supergravities with dilaton and a q-form field-strength in arbitrary dimensions. The metrics are assumed to have the symmetries ISO(p+1) × SO(d-p-2,1) and can be regarded as those of the magnetically charged Euclidean or space-like branes. When we impose the extremality condition, we find that the magnetic charges of the branes become imaginary and the corresponding real solutions then represent the Ep-branes of type II^∗ theories (for the field-strengths belonging to the RR sector). On the other hand, when the extremality condition is relaxed we find real solutions in type II theories which resemble the solutions found by Kruczenski-Myers-Peet. In d=10 they match exactly. We point out the relations between the solutions found in this paper and those of Chen-Gal'tsov-Gutperle in arbitrary dimensions. Although there is no extremal limit for these solutions, we find another class of solutions, wh...
Following Bai:2006vv we here consider the supergravity solutions representing the charged non-sup... more Following Bai:2006vv we here consider the supergravity solutions representing the charged non-supersymmetric p-brane (for 1≤ p ≤ 6) intersecting with chargeless non-supersymmetric 1-brane and 0-brane of type II string theories. We show how these solutions nicely interpolate between black p-branes and the Kaluza-Klein "bubble of nothing" (BON) by continuously varying some parameters characterizing the solutions from one set of values to another. By performing a time symmetric general bubble initial data analysis, we show that the interpolation implies a possible transition from black p-branes to KK BON only for p≤ 4, as in these cases there exist locally stable static bubbles under certain conditions. However, for p>4, black branes always decay into dynamical bubbles. Contrary to what is known in the literature, we argue that under certain conditions, the mechanism causing this transition to stable static bubbles can be the closed string tachyon condensation for all p≤ 4...
We construct non-supersymmetric p-brane solutions of type II supergravities in arbitrary dimensio... more We construct non-supersymmetric p-brane solutions of type II supergravities in arbitrary dimensions (d) delocalized in one of the spatial transverse directions. By a Wick rotation we convert these solutions into Euclidean p-branes delocalized in the transverse time-like direction. The former solutions in d=10 nicely interpolate between the (p+1)-dimensional non-BPS D-branes and the p-dimensional BPS D-branes very similar to the picture of tachyon condensation for the tachyonic kink solution on the non-BPS D-branes. On the other hand the latter solutions interpolate between the (p+1)-dimensional non-BPS D-branes and the tachyon matter supergravity configuration very similar to the picture of rolling tachyon on the non-BPS D-branes.
By using the gauge/gravity duality and the Maldacena prescription we compute the expectation valu... more By using the gauge/gravity duality and the Maldacena prescription we compute the expectation values of the Wilson loops in noncommutative Yang-Mills (NCYM) theory in (3+1) dimensions. We consider both the time-like and the light-like Wilson loops. The gravity dual background is given by a particular decoupling limit of (D1,D3) bound state of type IIB string theory. We obtain the velocity dependent quark-antiquark potential and numerically study how the dipole length and the potential change with velocity (for 0 < v < 1, i.e., the Wilson loop is time-like) of the dipole as well as noncommutativity. We discuss and compare the results with the known commutative results. We also obtain an analytic expression for the screening length when the rapidity is large and the noncommutativity parameter is small with the product remaining small. When v \rightarrow 1, the time-like Wilson loop becomes light-like and in that case we obtain the form of the jet quenching parameter for the stron...
A particular decoupling limit of non-extremal (D1, D3) brane bound state system of type IIB strin... more A particular decoupling limit of non-extremal (D1, D3) brane bound state system of type IIB string theory is known to give the gravity dual of space-space non- commutative Yang-Mills (NCYM) theory at finite temperature. We use a string probe in this background to compute the jet quenching parameter in the strongly coupled plasma of hot non-commutative Yang-Mills theory in (3+1)-dimensions from gauge/gravity duality. We give the expressions for the jet quenching parameter for both small and large non-commutativity. For small non-commutativity, we find that the value of the jet quenching parameter gets reduced from its commutative value. The reduction is enhanced with temperature as T^7 for fixed non-commutativity and the fixed 't Hooft coupling. We further generalize the results for the non-commutative Yang-Mills theories in diverse dimensions.
U-duality p-branes in toroidally compactified type II superstring theories in space-time dimensio... more U-duality p-branes in toroidally compactified type II superstring theories in space-time dimensions 10> D ≥ 4 can be constructed explicitly based on the conjectured U-duality symmetries and the corresponding known single-charge super p-brane configurations. As concrete examples, we first construct explicitly the SL(3,Z) superstrings and SL(3,Z) × SL(2,Z) 0-branes as well as their corresponding magnetic duals in D = 8. For the SL(3,Z) superstrings (3-branes), each of them is characterized by a triplet of integers corresponding to the electric-like (magneticlike) charges associated with the three 2-form gauge potentials present in the theory. For the SL(3,Z) × SL(2,Z) 0-branes (4-branes), each of them is labelled by a pair of triplets of integers corresponding to the electric-like (magnetic-like) charges associated with the two sets of three 1-form gauge potentials. The string (3-brane) tension and central charge are shown to be given by SL(3,Z) invariant expressions. It is argued ...
We show directly in the Lax operator approach how the Virasoro and W-constraints on the τ-functio... more We show directly in the Lax operator approach how the Virasoro and W-constraints on the τ-function arise in the p-reduced KP hierarchy or Generalized KdV hierarchy. In particular, we consider the KdV and the Boussinesq hierarchy to show that the Virasoro and the W-constraints follow from the string equation by expanding the “additional symmetry” operator in terms of the Lax operator. We also mention how this method could be generalized for higher KdV hierarchies. (∗) Address after 1st November 1992: Institute for Theoretical Physics, Groningen University,
It is known from the work in [1] of Lu et. al. that the non-supersymmetric charged D3-brane (with... more It is known from the work in [1] of Lu et. al. that the non-supersymmetric charged D3-brane (with anisotropies in time as well as one of the spatial directions of D3-brane) of type IIB string theory is characterized by five independent parameters. By fixing one of the parameters and zooming into a particular region of space-time we construct a four parameter family of solution in AdS5, which interpolates between AdS5 black hole and AdS5 soliton (when one of spatial directions in the Poincare coordinates is compact) by continuously changing the parameters (there is no need to take a double Wick rotation as is usual to go from one solution to the other) from one set of values to another. We consider two cases. In the first case the dilaton is constant for this transition and there are only three independent parameters, whereas in the second case the dilaton varies and there are four independent parameters. In the latter case, the solution interpolates between AdS5 black hole, AdS5 sol...
We construct a four dimensional de Sitter space upto a conformal transformation by compactifying ... more We construct a four dimensional de Sitter space upto a conformal transformation by compactifying the anisotropic SD3-brane solution of type IIB string theory on a six dimensional product space of the form H_5 × S^1, where H_5 is a five dimensional hyperbolic space and S^1 is a circle. The radius of the hyperbolic space is chosen to be constant. The radius of the circle and the dilaton in four dimensions are time dependent and not constant in general. By different choices of parameters characterizing the SD3-brane solution either the dilaton or the radius of the circle can be made constant but not both. The form-field is also non-vanishing in general, but it can be made to vanish without affecting the solution. This construction might be useful for a better understanding of dS/CFT correspondence as well as for cosmology.
We construct the intersecting non-supersymmetric (non-susy) D1/D5 solution of type IIB string the... more We construct the intersecting non-supersymmetric (non-susy) D1/D5 solution of type IIB string theory. While, as usual, the solution is charged under an electric two-form and an electric six-form gauge field, it also contains a non-susy chargeless (non-BPS) D0-brane. The S-dual of this solution is the non-susy F/NS5 solution. We show how these solutions nicely interpolate between the corresponding black (or non-extremal) solutions and the Kaluza-Klein (KK) "bubble of nothing" (BON) by continuously changing some parameters characterizing the solutions from one set of values to another. We show, by a time symmetric general bubble initial data analysis, that the final bubbles in these cases are static and stable and the interpolations can be physically interpreted as closed string tachyon condensation. As special cases, we recover the transition of two charge black F-string to BON, considered by Horowitz, and also the transition from AdS_3 black hole to global AdS_3.
In a previous work, we have shown that, like BPS Dp branes, bulk gravity gets decoupled from the ... more In a previous work, we have shown that, like BPS Dp branes, bulk gravity gets decoupled from the brane even for the non-susy Dp branes of type II string theories indicating a possible extension of AdS/CFT correspondence for the non-supersymmetric case. In that work, the decoupling of gravity on the non-susy Dp branes has been shown numerically for the general case as well as analytically for some special case. Here we discuss the decoupling limit and the throat geometry of the non-susy D3 brane when the charge associated with the brane is very large. We show that in the decoupling limit the throat geometry of the non-susy D3 brane, under appropriate coordinate change, reduces to the Constable-Myers solution and thus confirming that this solution is indeed the holographic dual of a (non-gravitational) gauge theory discussed there. We also show that when one of the parameters of the solution takes a specific value, it reduces, under another coordinate change, to the five-dimensional s...
We show that the (M5, M2, M2', MW) bound state solution of eleven dimensional supergravity re... more We show that the (M5, M2, M2', MW) bound state solution of eleven dimensional supergravity recently constructed in hep-th/0009147 is related to the (M5, M2) bound state one by a finite Lorentz boost along a M5-brane direction perpendicular to the M2-brane. Given the (M5, M2) bound state as a defining system for OM theory and the above relation between this system and the (M5, M2, M2', MW) bound state, we test the recently proposed V-duality conjecture in OM theory. Insisting to have a decoupled OM theory, we find that the allowed Lorentz boost has to be infinitesimally small, therefore resulting in a family of OM theories related by Galilean boosts. We argue that such related OM theories are equivalent to each other. In other words, V-duality holds for OM theory as well. Upon compactification on either an electric or a `magnetic' circle (plus T-dualities as well), the V-duality for OM theory gives the known one for either noncommutative open string theories or noncommuta...
We consider the space-like Dp brane solutions of type II string theories having isometries ISO(p+... more We consider the space-like Dp brane solutions of type II string theories having isometries ISO(p+1) × SO(8-p,1). These are asymptotically flat solutions or in other words, the metrics become flat at the time scale τ≫τ_0. On the other hand, when τ∼τ_0, we get (p+1)+1 dimensional flat FLRWmetrics upon compactification on a (8-p) dimensional hyperbolic space with time dependent radii. We show that the resultant (p+1)+1 dimensional metrics describe transient accelerating cosmologies for all p from 1 to 6, i.e., from (2+1) to (7+1) space-time dimensions. We show how the acceleration changes with the interplay of the various parameters characterizing the solutions in (3+1) dimensions. Finally, for τ≪τ_0, after compactification on (8-p) dimensional hyperbolic space, the resultant metrics are shown to take the form of (p+1)+1 dimensional de Sitter spaces upto a conformal transformation. Cosmologies here are decelerating, but, only in a particular conformal frame we get eternal acceleration.
This is a companion paper of our previous work [1] where we studied the thermodynamics and phase ... more This is a companion paper of our previous work [1] where we studied the thermodynamics and phase structure of asymptotically flat black p-branes in a cavity in arbitrary dimensions D in a canonical ensemble. In this work we study the thermodynamics and phase structure of the same in a grand canonical ensemble. Since the boundary data in two cases are different (for the grand canonical ensemble boundary potential is fixed instead of the charge as in canonical ensemble) the stability analysis and the phase structure in the two cases are quite different. In particular, we find that there exists an analog of one-variable analysis as in canonical ensemble, which gives the same stability condition as the rather complicated known (but generalized from black holes to the present case) two-variable analysis. When certain condition for the fixed potential is satisfied, the phase structure of charged black p-branes is in some sense similar to that of the zero charge black p-branes in canonical...
We compute the expectation values of both the time-like and the light-like Wilson loops in a stro... more We compute the expectation values of both the time-like and the light-like Wilson loops in a strongly coupled plasma of (p+1)-dimensional Yang-Mills theories using gravity/gauge theory correspondence. From the time-like Wilson loop we obtain the velocity dependent quark-antiquark potential where the dipole is moving through the plasma with an arbitrary velocity 0<v<1 and also obtain expressions for the screening lengths. When the velocity v--> 1, the Wilson loop becomes light-like and we obtain the form of the jet quenching parameter in those strongly coupled plasma.
It was shown in Dey and Roy (2012) that the near horizon limit of the 1/4 BPS threshold F-Dp (for... more It was shown in Dey and Roy (2012) that the near horizon limit of the 1/4 BPS threshold F-Dp (for 0≤ p ≤ 5, p ≠ 4) bound state solutions of type II string theories give rise to space-time metrics endowed with Lifshitz scaling along with hyperscaling violation. Here we compute the holographic entanglement entropy of this system for all p ≠ 4 (for p=4 the space-time has AdS_2 structure). For p=3,5, we get the expected area law behavior of the entanglement entropy. For p=0,1, the entanglement entropy has new area law violations and has the behavior which is in between the linear and logarithmic behaviors. For p=2, we get a logarithmic violation of the area law. We also compute the entanglement entropy at finite temperature and show that as the temperature rises, the entanglement entropy makes a crossover to the thermal entropy of the system. We thus obtain the string theoretic realization of holographic EE and various of its aspects noted earlier for generic metric with hyperscaling vi...
It is found that a necessary completion of phase structure of D-dimensional charged black p-brane... more It is found that a necessary completion of phase structure of D-dimensional charged black p-brane (p > 0) in a cavity requires two additional thermodynamical phases, the so-called "bubble of nothing" and/or the extremal brane, in canonical ensemble. This finding resolves the puzzle about the missing phases which are needed for the underlying phase diagram when d̃ = D - p - 3 ≤ 2 and gives a new (bubble) phase which can become globally stable when d̃ > 2. An analog of Hawking-Page transition is also found among other new phase transitions, giving a complete phase structure in this setup.
By using the non-supersymmetric p-brane solutions delocalized in arbitrary number of transverse d... more By using the non-supersymmetric p-brane solutions delocalized in arbitrary number of transverse directions in type II supergravities, we show how they can be regarded as interpolating solutions between unstable Dp-branes (a non-BPS D-brane or a pair of coincident D-brane-antiD-brane) and fundamental strings and also between unstable Dp-branes and NS5-branes. We also show that some of these solutions can be regarded as interpolating solutions between NS5/N̅S̅5 and Dp-branes (for p ≤ 5). This gives a closed string description of the tachyon condensation and lends support to the conjecture that the open string theory on unstable D-branes at the tachyonic vacuum has soliton solutions describing not only the lower dimensional BPS D-branes, but also the fundamental strings as well as the NS5-branes.
By directly solving the equations of motion we obtain the time dependent solutions of supergravit... more By directly solving the equations of motion we obtain the time dependent solutions of supergravities with dilaton and a q-form field-strength in arbitrary dimensions. The metrics are assumed to have the symmetries ISO(p+1) × SO(d-p-2,1) and can be regarded as those of the magnetically charged Euclidean or space-like branes. When we impose the extremality condition, we find that the magnetic charges of the branes become imaginary and the corresponding real solutions then represent the Ep-branes of type II^∗ theories (for the field-strengths belonging to the RR sector). On the other hand, when the extremality condition is relaxed we find real solutions in type II theories which resemble the solutions found by Kruczenski-Myers-Peet. In d=10 they match exactly. We point out the relations between the solutions found in this paper and those of Chen-Gal'tsov-Gutperle in arbitrary dimensions. Although there is no extremal limit for these solutions, we find another class of solutions, wh...
Following Bai:2006vv we here consider the supergravity solutions representing the charged non-sup... more Following Bai:2006vv we here consider the supergravity solutions representing the charged non-supersymmetric p-brane (for 1≤ p ≤ 6) intersecting with chargeless non-supersymmetric 1-brane and 0-brane of type II string theories. We show how these solutions nicely interpolate between black p-branes and the Kaluza-Klein "bubble of nothing" (BON) by continuously varying some parameters characterizing the solutions from one set of values to another. By performing a time symmetric general bubble initial data analysis, we show that the interpolation implies a possible transition from black p-branes to KK BON only for p≤ 4, as in these cases there exist locally stable static bubbles under certain conditions. However, for p>4, black branes always decay into dynamical bubbles. Contrary to what is known in the literature, we argue that under certain conditions, the mechanism causing this transition to stable static bubbles can be the closed string tachyon condensation for all p≤ 4...
We construct non-supersymmetric p-brane solutions of type II supergravities in arbitrary dimensio... more We construct non-supersymmetric p-brane solutions of type II supergravities in arbitrary dimensions (d) delocalized in one of the spatial transverse directions. By a Wick rotation we convert these solutions into Euclidean p-branes delocalized in the transverse time-like direction. The former solutions in d=10 nicely interpolate between the (p+1)-dimensional non-BPS D-branes and the p-dimensional BPS D-branes very similar to the picture of tachyon condensation for the tachyonic kink solution on the non-BPS D-branes. On the other hand the latter solutions interpolate between the (p+1)-dimensional non-BPS D-branes and the tachyon matter supergravity configuration very similar to the picture of rolling tachyon on the non-BPS D-branes.
By using the gauge/gravity duality and the Maldacena prescription we compute the expectation valu... more By using the gauge/gravity duality and the Maldacena prescription we compute the expectation values of the Wilson loops in noncommutative Yang-Mills (NCYM) theory in (3+1) dimensions. We consider both the time-like and the light-like Wilson loops. The gravity dual background is given by a particular decoupling limit of (D1,D3) bound state of type IIB string theory. We obtain the velocity dependent quark-antiquark potential and numerically study how the dipole length and the potential change with velocity (for 0 < v < 1, i.e., the Wilson loop is time-like) of the dipole as well as noncommutativity. We discuss and compare the results with the known commutative results. We also obtain an analytic expression for the screening length when the rapidity is large and the noncommutativity parameter is small with the product remaining small. When v \rightarrow 1, the time-like Wilson loop becomes light-like and in that case we obtain the form of the jet quenching parameter for the stron...
A particular decoupling limit of non-extremal (D1, D3) brane bound state system of type IIB strin... more A particular decoupling limit of non-extremal (D1, D3) brane bound state system of type IIB string theory is known to give the gravity dual of space-space non- commutative Yang-Mills (NCYM) theory at finite temperature. We use a string probe in this background to compute the jet quenching parameter in the strongly coupled plasma of hot non-commutative Yang-Mills theory in (3+1)-dimensions from gauge/gravity duality. We give the expressions for the jet quenching parameter for both small and large non-commutativity. For small non-commutativity, we find that the value of the jet quenching parameter gets reduced from its commutative value. The reduction is enhanced with temperature as T^7 for fixed non-commutativity and the fixed 't Hooft coupling. We further generalize the results for the non-commutative Yang-Mills theories in diverse dimensions.
Uploads
Papers by Shibaji Roy