The flow of homogeneous fluids through porous media: analogies with other physical problems

http://cds.cern.ch/record/994225/files/0610327.pdf

Four-dimensional string compactifications with D-branes, orientifolds and fluxes

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.

/pdf/the-topological-vertex-3lrad1kwkt.pdf

The Topological Vertex

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.

/pdf/moduli-spaces-of-local-systems-and-higher-teichmuller-theory-36h32nsutb.pdf

Moduli spaces of local systems and higher Teichmüller theory

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.

https://iopscience.iop.org/article/10.1088/1126-6708/2003/05/046/pdf

The statistics of string/M theory vacua

The global lifestyle of this modern world has become more dependent on petroleum-based products, whose applications are involved almost everywhere. Since a large quantity of oil is being used on a daily basis, the spilling of oil by various means during its storage and transportation has become inevitable. This work focuses on the spilling of oil in a marine environment, generally referred to as an offshore oil spill, in contrast to an onshore oil spill associated with a terrestrial environment. These oil spills not only devastate the natural resources and unsettle the economy, they also jeopardize marine life, as well as human health. The remediation of an oil spill remains very challenging, when the disaster is associated with a large aerial extent. In this context, a sound understanding is required on the origin, seeping, composition and properties of the spilled oil in order to better monitor the spreading of the oil spill. In this manuscript, a detailed list of fundamental queries, which will be required to be addressed at the instance of an oil spill has been deduced, which will be extremely useful for the oil spill respondents as there are no previous studies that exclusively provide the type and nature of data required to be collected, immediately following an oil spill. Furthermore, this manuscript has deduced a list of sensitive and essential plots that will be required in order to analyse and forecast the spreading of an oil spill. An essence of weathering and its associated movement of oil spill has been included.

/pdf/oil-spill-in-a-marine-environment-requirements-following-an-4p5ob6cnwy.pdf

Oil spill in a marine environment: requirements following an offshore oil spill

We systematically study and obtain the large-volume analogues of fractional two-branes on resolutions of orbifolds C^3/Z_n. We 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 C^3/Z_3 and C^3/Z_5.

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

We present a geometric interpretation for the torsion constraints in (2,0) supergravity using G-structures. This leads to a classification of the constraints as given by Ref. 1. We also present the essential torsion constraints for (p,q) geometry.

http://www.physics.iitm.ac.in/~suresh/sgtalk/talk_html/torsion.pdf

A geometric interpretation for the torsion constraints of (2,0) heterotic worldsheet supergravity

We consider Landau-Ginzburg (LG) models with boundary conditions preserving A-type N=2 supersymmetry. We show the equivalence of a linear class of boundary conditions in the LG model to a particular class of boundary states in the corresponding CFT by an explicit computation of the open-string Witten index in the LG model. We extend the linear class of boundary conditions to general non-linear boundary conditions and determine their consistency with A-type N=2 supersymmetry. This enables us to provide a microscopic description of special Lagrangian submanifolds in C^n due to Harvey and Lawson. We generalise this construction to the case of hypersurfaces in P^n. We find that the boundary conditions must necessarily have vanishing Poisson bracket with the combination (W(\phi)-\bar{W}(\bar{\phi})), where W(\phi) is the appropriate superpotential for the hypersurface. An interesting application considered is the T^3 supersymmetric cycle of the quintic in the large complex structure limit.

On the Landau-Ginzburg description of Boundary CFTs and special Lagrangian submanifolds

\n The present work focuses on the improvement of flow properties during the transportation of heavy oil via 0.0254-, 0.0381-, and 0.0508-m-diameter pipelines. The effect of temperature, water cut, natural extract Madhuca Longifolia (ML), and potato starch (PS) on pressure drop, shear viscosity, and flow behavior index (n) was experimentally investigated. Minimum pressure drop occurred in the 0.0508-m-inner-diameter (ID) pipeline because of the combined consequence of temperature and 2,000 ppm ML during the transportation of 85% heavy oil + 15% water. A new correlation was developed to predict the friction factor for the heavy oil/emulsions during its transportation in a 0.0254-m-ID pipeline using the linear regression method for friction factor. Flow behavior index inclined toward Newtonian from shear-thinning behavior (i.e., n = 0.2181 to 0.9834) after the addition of 2,000 ppm ML at 50°C. From the comparative studies of the bioadditives ML and PS, it was found that ML was more effective in decreasing pressure drop. A new hybrid artificial intelligence (AI) technique was developed and used to optimize flow-influencing parameters to minimize the pressure drop and shear viscosity and improve flow behavior index. Minimum pressure drop (58,659.72 Pa), shear viscosity (1.56 Pa·s), and maximum flow behavior index (0.71) were achieved during the heavy oil flow in the 0.0508-m-ID pipeline after addition of 15% water, 1,320 ppm ML for 12.33-m3/h flow rate at 27°C. ML and PS are substantially efficient enough to decrease the pressure drop and shear viscosity and increase the flow behavior index in pipelines. However, from the studies, it was concluded that ML shows better performance compared with PS. Because both ML and PS are biodegradable and nontoxic, the petroleum industry may use both as a cost-effective alternative to decrease pour point and improve flowability for heavy crude oil.

Suresh Govindarajan

Papers

Oil spill in a marine environment: requirements following an offshore oil spill

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

A geometric interpretation for the torsion constraints of (2,0) heterotic worldsheet supergravity

On the Landau-Ginzburg description of Boundary CFTs and special Lagrangian submanifolds

Remediation of Heavy Oil Transportation Problems via Pipelines Using Biodegradable Additives: An Experimental and Artificial Intelligence Approach