Suresh Govindarajan

Bio: Suresh Govindarajan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Superpotential & Siegel modular form. The author has an hindex of 21, co-authored 130 publications receiving 1500 citations. Previous affiliations of Suresh Govindarajan include University of Pennsylvania & Indian Institutes of Technology.

Heterotic M(atrix) theory at generic points in Narain moduli space

Abstract: Type II compactifications with varying string coupling can be described elegantly in F-theory/M-theory as compactifications on U - manifolds. Using a similar approach to describe Super Yang-Mills with a varying coupling constant, we argue that at generic points in Narain moduli space, the $E_8 \times E_8$ Heterotic string compactified on $T^2$ is described in M(atrix) theory by N=4 SYM in 3+1 dimensions with base $S^1 \times CP^1$ and a holomorphically varying coupling constant. The $CP^1$ is best described as the base of an elliptic K3 whose fibre is the complexified coupling constant of the Super Yang-Mills theory leading to manifest U-duality. We also consider the cases of the Heterotic string on $S^1$ and $T^3$. The twisted sector seems to (almost) naturally appear at precisely those points where enhancement of gauge symmetry is expected and need not be postulated. A unifying picture emerges in which the U-manifolds which describe type II orientifolds (dual to the Heterotic string) as M- or F- theory compactifications play a crucial role in Heterotic M(atrix) theory compactifications.

Interaction of dissolution, sorption and biodegradation on transport of BTEX in a saturated groundwater system: Numerical modeling and spatial moment analysis

Abstract: Interaction of various physical, chemical and biological transport processes plays an important role in deciding the fate and migration of contaminants in groundwater systems. In this study, a numerical investigation on the interaction of various transport processes of BTEX in a saturated groundwater system is carried out. In addition, the multi-component dissolution from a residual BTEX source under unsteady flow conditions is incorporated in the modeling framework. The model considers Benzene, Toluene, Ethyl Benzene and Xylene dissolving from the residual BTEX source zone to undergo sorption and aerobic biodegradation within the groundwater aquifer. Spatial concentration profiles of dissolved BTEX components under the interaction of various sorption and biodegradation conditions have been studied. Subsequently, a spatial moment analysis is carried out to analyze the effect of interaction of various transport processes on the total dissolved mass and the mobility of dissolved BTEX components. Results from the present numerical study suggest that the interaction of dissolution, sorption and biodegradation significantly influence the spatial distribution of dissolved BTEX components within the saturated groundwater system. Mobility of dissolved BTEX components is also found to be affected by the interaction of these transport processes.

Mathematical Modeling on Mobility and Spreading of BTEX in a Discretely Fractured Aquifer System Under the Coupled Effect of Dissolution, Sorption, and Biodegradation

Abstract: This paper presents a numerical model to investigate the migration of BTEX (benzene, toluene, ethylbenzene, and xylene) within a fractured aquifer system at the scale of a single fracture under the coupled effect of various transport processes such as dissolution, sorption, biodegradation. The developed model also considers the influence of equilibrium- and kinetic-controlled sorption scenarios on BTEX transport. Further, the transport characteristics of dissolved BTEX within the fracture–matrix system (FMS) are obtained by carrying out the spatial moment analysis on the concentration profiles simulated. In this study, the spatial moment analysis is conducted to estimate the following transport characteristics of dissolved BTEX: (a) velocity within the fracture, (b) dispersion coefficient within the fracture, (c) dissolved mass within the matrix. In order to investigate the sensitivity of various input parameters, two sensitivity indices are computed based on the variation in the velocity of dissolved BTEX constituent within the fracture (SI_vel) and on the variation in the dissolved mass of BTEX constituents within the matrix (SI_mat). Results from the present simulation study suggest that the sorption and biodegradation reactions influence the concentration distribution of highly soluble BTEX constituents (benzene, toluene) within the FMS significantly. The influence of biodegradation on the migration of BTEX within the FMS is found to be more when it co-occurs with the sorption reaction. The effect of sorption and biodegradation reactions on the mobility and dispersion coefficient of dissolved BTEX constituents within the FMS is found to be significant during the early simulation period.

Chemical Affinity Modeling of Methane Hydrate Formation and Dissociation in the Presence of Surfactants

Abstract: Methane hydrate formation, dissociation and its kinetics after addition of Sodium Dodecyl Benzene Sulfonate (SDBS), Cetyl-Tri-methyl Ammonium Bromide (CTAB) and Tergitol in aqueous phase have been investigated experimentally along with the storage capacity. The experiments were carried out with surfactant concentrations varying between 0 and 10000 ppm in the aqueous phase. Nucleation temperature, pressure, dissociation temperature and point, pressure drops, formation rate and storage capacity were significantly varied following by the addition of surfactants in aqueous phase during hydrate formation and dissociation. Maximum sub-cooling was required for the nucleation after addition of 5000 ppm of SDBS. Hydrate formation rate and rate constants has been found to increase with the addition of surfactants, while the same gets reduced with time. Formation rate increases 443 folds after addition of 10000 ppm SDBS in aqueous phase. Maximum storage capacity occurred at 1000 ppm of SDBS in aqueous phase and then...

Fractional two-branes, toric orbifolds and the quantum McKay correspondence

Abstract: We systematically study and obtain the large-volume analogues of fractional two-branes on resolutions of the orbifolds 3/n. We also study a generalisation of the McKay correspondence proposed in hep-th/0504164 called the quantum McKay correspondence by constructing duals to the fractional two-branes. Details are explicitly worked out for two examples – the crepant resolutions of 3/3 and 3/5.

The Topological Vertex

Abstract: We construct a cubic field theory which provides all genus amplitudes of the topological A-model for all non-compact toric Calabi-Yau threefolds. The topology of a given Feynman diagram encodes the topology of a fixed Calabi-Yau, with Schwinger parameters playing the role of Kahler classes of the threefold. We interpret this result as an operatorial computation of the amplitudes in the B-model mirror which is the quantum Kodaira-Spencer theory. The only degree of freedom of this theory is an unconventional chiral scalar on a Riemann surface. In this setup we identify the B-branes on the mirror Riemann surface as fermions related to the chiral boson by bosonization.

Moduli spaces of local systems and higher Teichmüller theory

Abstract: Let G be a split semisimple algebraic group over Q with trivial center. Let S be a compact oriented surface, with or without boundary. We define positive representations of the fundamental group of S to G(R), construct explicitly all positive representations, and prove that they are faithful, discrete, and positive hyperbolic; the moduli space of positive representations is a topologically trivial open domain in the space of all representations. When S have holes, we defined two moduli spaces closely related to the moduli spaces of G-local systems on S. We show that they carry a lot of interesting structures. In particular we define a distinguished collection of coordinate systems, equivariant under the action of the mapping class group of S. We prove that their transition functions are subtraction free. Thus we have positive structures on these moduli spaces. Therefore we can take their points with values in any positive semifield. Their positive real points provide the two higher Teichmuller spaces related to G and S, while the points with values in the tropical semifields provide the lamination spaces. We define the motivic avatar of the Weil–Petersson form for one of these spaces. It is related to the motivic dilogarithm.

The statistics of string/M theory vacua

Abstract: We discuss systematic approaches to the classification of string/M theory vacua, and physical questions this might help us resolve. To this end, we initiate the study of ensembles of effective Lagrangians, which can be used to precisely study the predictive power of string theory, and in simple examples can lead to universality results. Using these ideas, we outline an approach to estimating the number of vacua of string/M theory which can realize the Standard Model.