arXiv subjects

Koushik Ganesan

Publications and source records attributed to Koushik Ganesan.

6 recordsLinked to original sources

arXiv2023

Analogue viscous current flow near the onset of superconductivity

Spatially resolved transport in two-dimensional quantum materials can reveal dynamics which is invisible in conventional bulk transport measurements. We predict striking patterns in spatially inhomogeneous transport just above the critical temperature in two-dimensional superconducting thin films, where electrical current will appear to flow as if it were a viscous fluid obeying the Navier-Stokes equations. Compared to viscous electron fluids in ultrapure metals such as graphene, this analogue viscous vortex fluid can exhibit a far more tunable crossover, as a function of temperature, from Ohmic to non-Ohmic transport, with the latter arising on increasingly large length scales close to the critical temperature. Experiments using nitrogen vacancy center magnetometry, or transport through patterned thin films, could reveal this analogue viscous flow in a wide variety of materials.

cond-mat.supr-con↗

arXiv2022

Spatial Distribution of Solar PV Deployment: An Application of the Region-Based Convolutional Neural Network

This paper presents a comprehensive analysis of the social and environmental determinants of solar photovoltaic (PV) deployment rates in Colorado, USA. Using 652,795 satellite imagery and computer vision frameworks based on a convolutional neural network, we estimated the proportion of households with solar PV systems and the roof areas covered by solar panels. At the census block group level, 7% of Coloradan households have a rooftop PV system, and 2.5% of roof areas in Colorado are covered by solar panels as of 2021. Our machine learning models predict solar PV deployment based on 43 natural and social characteristics of neighborhoods. Using four algorithms (Random Forest, CATBoost, LightGBM, XGBoost), we find that the share of Democratic party votes, hail risks, strong wind risks, median home value, and solar PV permitting timelines are the most important predictors of solar PV count per household. In addition to the size of the houses, PV-to-roof area ratio is highly dependent on solar PV permitting timelines, proportion of renters and multifamily housing, and winter weather risks. We also find racial and ethnic disparities in rooftop solar deployment. The average marginal effects of median household income on solar deployment are lower in communities with a greater proportion of African American and Hispanic residents and are higher in communities with a greater proportion of White and Asian residents. In the ongoing energy transition, knowing the key predictors of solar deployment can better inform business and policy decision making for more efficient and equitable grid infrastructure investment and distributed energy resource management.

cs.CY↗

arXiv2021

Renormalization group in quantum critical theories with Harris-marginal disorder

We develop a renormalization group for weak Harris-marginal disorder in otherwise strongly interacting quantum critical theories, focusing on systems which have emergent conformal invariance. Using conformal perturbation theory, we argue that previously proposed random lines of fixed points with Lifshitz scaling in fact flow towards other universal fixed points, and this flow is captured by a "one-loop" analysis. Our approach appears best controlled in theories with only a few operators with low scaling dimension. In this regime, we compare our predictions for the flow of disorder to holographic models, and find complete agreement.

hep-th↗

arXiv2020

Holographic subdiffusion

We initiate a study of finite temperature transport in gapless and strongly coupled quantum theories with charge and dipole conservation using gauge-gravity duality. In a model with non-dynamical gravity, the bulk fields of our model include a suitable mixed-rank tensor which encodes the boundary multipole symmetry. We describe how such a theory can arise at low energies in a theory with a covariant bulk action. Studying response functions at zero density, we find that charge relaxes via a fourth-order subdiffusion equation, consistent with a recently-developed field-theoretic framework.

hep-th↗

arXiv2020

Public Sentiment Toward Solar Energy: Opinion Mining of Twitter Using a Transformer-Based Language Model

Public acceptance and support for renewable energy are important determinants of renewable energy policies and market conditions. This paper examines public sentiment toward solar energy in the United States using data from Twitter, a micro-blogging platform in which people post messages, known as tweets. We filtered tweets specific to solar energy and performed a classification task using Robustly optimized Bidirectional Encoder Representations from Transformers (RoBERTa). Analyzing 71,262 tweets during the period of late January to early July 2020, we find public sentiment varies significantly across states. Within the study period, the Northeastern U.S. region shows more positive sentiment toward solar energy than did the Southern U.S. region. Solar radiation does not correlate to variation in solar sentiment across states. We also find that public sentiment toward solar correlates to renewable energy policy and market conditions, specifically, Renewable Portfolio Standards (RPS) targets, customer-friendly net metering policies, and a mature solar market.

cs.CL↗

arXiv2020

Breakdown of emergent Lifshitz symmetry in holographic matter with Harris-marginal disorder

We revisit the theory of strongly correlated quantum matter perturbed by Harris-marginal random-field disorder, using the simplest holographic model. We argue that for weak disorder, the ground state of the theory is not Lifshitz invariant with a non-trivial disorder-dependent dynamical exponent, as previously found. Instead, below a non-perturbatively small energy scale, we predict infrared physics becomes independent of the disorder strength.

hep-th↗