arXiv subjects
Publications and source records attributed to Harvendra Singh.
We consider de Sitter spacetime solutions and the corresponding de Sitter kind of plane-wave solutions in M* theory. We attempt to write down corresponsing matrix model which is found to have explicit negative energy mass terms as well as negative energy kinetic terms for the matrix fields.
In this note we aim to study plane-wave limits of the solutions of type II$^*$ superstring theories. We consider Freund-Rubin type $dS_5\times H^5$ solutions of type IIB$^*$ theory and obtain a new kind of plane-wave solutions, we refer them as de Sitter plane-waves or Dpp-waves. Considering Hull's time-like T-duality we are able to map the Dpp wave solution to maximally supersymmetric Hpp-wave in IIB string theory and vice-versa.
In this paper we construct generalised Penrose limits for the solutions of massive type IIA supergravity. We consider a Freund-Rubin type solution and apply these {\it massive} Penrose limits and obtain supersymmetric pp-wave which is a standard type IIA background. We point out that results in this paper are easily generalised for the cases of gauged supergravities.
In this paper we study half-supersymmetric (D6,D8) bound state brane configuration of massive type IIA supergravity. We show that this bound state can also be generated by using massive T-duality rules of type-II supergravities in D=9, starting from D7-branes. We write down corresponding Killing spinors and find that these backgrounds indeed preserve 16 supersymmetries like any other D$p$-brane bound state with $B$-field. We also make a point on the massive nature of the $B$-field in this background. The Seiberg-Witten limits to obtain 9-dimensional NCYMs are also discussed, but the full understanding of such gauge theories remains unanswered.
We construct M5-branes in pp-wave background and find that they preserve exactly half of the background pp-wave supersymmetries. We explicitly write down the standard as well as supernumerary Killing spinors and find that their respective numbers are also half of those for the pp-wave background. This is in line with the recent work of Dabholkar et.al. which shows half-supersymmetric D-branes can be constructed in Hpp-wave background.
We study $T^2$ compactification of massive type IIA supergravity in presence of possible Ramond-Ramond (RR) background fluxes. The resulting theory in D=8 is shown to possess full $SL(2,R)\times SL(2,R)$ T-duality symmetry similar to the massless case. It is shown that elements of duality symmetry interpolate between massive type IIA compactified on $T^2$ and ordinary type IIA compactified on $T^2$ with RR 2-form flux. We also discuss relationship between M-theory vacua and massive type IIA vacua. The D8-brane is found to correspond to M-theory `pure gravity' solution which is a direct product of 7-dimensional Minkowski space and a 4-dimensional instanton. We also construct D6-D8 bound state which preserves 1/2 supersymmetries. We then discuss massive IIA compactification on $T^4$ and point out that when all possible RR fluxes on $T^4$ are turned on the six-dimensional theory appears to assume a nice SO(4,4) invariant form.
In this paper we study $T^2$ compactification of 6-dimensional massive type IIA supergravity in presence of Ramond-Ramond background fluxes. The resulting theory in four dimensions is shown to possess $SL(2,R)\times SL(2,R)\times O(4,20)$ duality symmetry. It is shown that specific elements of this symmetry relate massive type IIA compactified on $K3\times T^2$ (with fluxes along $K3$) to the ordinary type IIA compactified on $K3\times T^2$ (with fluxes along $T^2$). In turn, this relationship is exploited to relate Romans theory to heterotic strings. The D8-brane (domain-wall) wrapped on $K3\times T^2$ is related to {\it pure gravity} heterotic solution which is a direct product of 6-dimensional flat spacetime and a 4-dimensional Taub-NUT instanton.
In this paper we study K3 compactification of ten-dimensional massive type IIA theory with all possible Ramond-Ramond background fluxes turned on. The resulting six-dimensional theory is a new massive (gauged) supergravity with an action that is manifestly invariant under an O(4,20) / (O(4) times O(20)) duality symmetry. We discover that this six-dimensional theory interpolates between vacua of ten-dimensional massive IIA supergravity and vacua of massless IIA supergravity with appropriate background fluxes turned on. This in turn suggests a new 11-dimensional interpretation for the massive type IIA theory.
We study Euclidean D=4, N=4 gauged $SU(2) \times SU(1,1)$ supergravity theory which has been obtained from dimensional reduction of N=1, D=10 supergravity on $S^3 \times AdS_3$. We obtain supersymmetric configurations like domain wall, electro-vac type of solutions with geometries $E^2 \times S^2$, $E^2 \times AdS_2$ and axio-vac type $E^1 \times S^3$ solution in this Euclidean Freedman-Schwarz (EFS) model. We also show that the Euclidean gravitational instantons with nontrivial (anti)self-dual U(1) gauge fields are stable vacua preserving one fourth of the original supersymmetry.
We perform explicitly the toroidal compactification of eleven dimensional supergravity to six dimensions and present its action in a manifestly $SO(5,5)\over SO(5)\times SO(5)$ invariant form using the recently proposed covariant formulation of theories involving chiral fields.
In this note we extend our work in a previous paper hep-th/9801038. We show here that various intersecting brane-like configurations can be found in the vacuum of $D=4, N=4$ supergravity with gauged R-symmetry group $SU(2)\times SU(2)$. These include intersections of domain-walls, strings and point-like objects. Some of these intersecting configurations preserve 1/2 and 1/4 of supersymmetry. We observe that the previously obtained $AdS_3\times R^1$ pure axionic vacuum or `axio-vac' is an intersection of domain-wall with extended string with 1/2 supersymmetries. Also the solutions known as `electro-vac' with geometry $AdS_2\times R^2$ can be simply interpreted as the intersection of domain-wall with point-like object.
In this paper we obtain supersymmetric brane-like configurations in the vacuum of N=4 gauged $SU(2)\times SU(2)$ supergravity theory in four spacetime dimensions. Almost all of these vacuum solutions preserve either half or one quarter of the supersymmetry in the theory. We also study the solutions in presence of nontrivial axionic and gauge field backgrounds. In the case of pure gravity with axionic charge the geometry of the spacetime is $AdS_3\times R^1$ with N=1 supersymmetry. An interesting observation is that the domain walls of this theory cannot be given an interpretation of a 2-brane in four dimensions. But it still exists as a stable vacuum. This feature is quite distinct from the domain-wall configuration in massive type IIA supergravity in ten dimensions.
In this report we obtain explicit string-like solutions of equations of motion of massive heterotic supergravity recently obtained by Bergshoeff, Roo and Eyras. We also find consistent string source which can be embedded in these backgrounds when space-time dimension is greater than or equal to six.
The order $g^5$ contribution to the pressure of massless $g^2 ϕ^4$ theory at nonzero temperature is obtained explicitly. Lower order contributions are reconsidered and two issues leading to the optimal choice of rearranged Lagrangian for such calculations are clarified.
We consider wormhole solutions in $2+1$ Euclidean dimensions. A duality transformation is introduced to derive a new action from magnetic wormhole action of Gupta, Hughes, Preskill and Wise. The classical solution is presented. The vertex operators corresponding to the wormhole are derived. Conformally coupled scalars and spinors are considered in the wormhole background and the vertex operators are computed. ( To be published in Phys. Rev. D15)