Ashutosh Dash

Goethe University Frankfurt

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Victor Roy

National Institute of Science Education and Research

Subhasis Samanta

Jan Kochanowski University

B. Mohanty

National Institute of Science Education and Research

Rajesh Biswas

Homi Bhabha National Institute

Najmul Haque

National Institute of Science Education and Research

Ankit Kumar Panda

National Institute of Science Education and Research

Amaresh Jaiswal

National Institute of Science Education and Research

Siddhesh B. Ghag

Center for Excellence in Basic Sciences

Victor Roy

Payal Mohanty

National Institute of Science Education and Research

Cooperative Institutions

Homi Bhabha National Institute

National Institute of Science Education and Research

Variable Energy Cyclotron Centre

Saha Institute of Nuclear Physics

Tata Institute of Fundamental Research

Physical Sciences (United States)

Goethe University Frankfurt

Physical Research Laboratory

Indian Institute of Technology Gandhinagar

Bose Institute

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Functional Renormalization Group analysis of the quark-condensation pattern on the Fermi surface: A simple effective-model approach

arXiv (Cornell University) (2024)

Kie Sang Jeong Fabrizio Murgana Ashutosh Dash Dirk H. Rischke

A simple effective model for the intermediate-density regime is constructed from the high-density effective theory of quantum chromodynamics (QCD). In the effective model, under a renormalization-group (RG) scaling towards low momenta, the original QCD interactions lead to four-quark contact interactions for the relevant quark and hole modes around the Fermi surface. The contact interaction in the scalar channel can be traced back to zero-sound-type collinear quark scattering near the Fermi surface in an instanton background. The quark and hole states in opposite directions of a given Fermi velocity form the collective scalar bosonic mode $\sigma$. The magnitude of $\sigma$ is investigated via the non-perturbative Functional Renormalization Group (FRG) evolution of the effective average action from the ultraviolet (UV) to the infrared (IR). In the mean background-field approximation for $\sigma$, nontrivial minima ($\bar{\sigma} \neq 0$) are found in the IR limit of the effective average action. A nonvanishing $\bar{\sigma}$ corresponds to condensation of quark and hole states in opposite directions of a given Fermi velocity, in a thin shell-like structure in momentum space around the Fermi surface. This looks similar to the shell-like baryon distribution in momentum space assumed in the quarkyonic-matter concept. However, when including a dynamic bosonic $\sigma$-mode in the RG flow, we find that its diffusive nature destroys the quark-hole condensate, i.e., the IR potential does not show any minima beyond the trivial one.

Functional renormalization group

10.48550/arxiv.2407.13589

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Flow correlation as a measure of phase transition: results from a new hydrodynamic code

arXiv (Cornell University) (2019)

Ashutosh Dash Victor Roy

Finding the existence and the location of the QCD critical point on the temperature T and baryon chemical potential $\mu_{b}$ plane is one of the main goals of the RHIC beam energy scan program. To make theoretical predictions and corroborate with the experimental data requires modelling the space-time evolution of the matter created in heavy-ion collisions by some dynamical models such as the relativistic hydrodynamics with a proper Equation of State (EoS). In the present exploratory study, we use a newly developed ideal 2+1 dimensional event-by-event (e-by-e) hydrodynamic code with two different Equation of State (EoS) (i) Lattice QCD + HRG EoS with a crossover transition, (ii) EoS with a first-order phase transition. Using the MC-Glauber model initial condition we calculate the event-by-event distribution of flow coefficients $v_{n}$ and eccentricities $\epsilon_{n}$ ($n=2-4$) for two different centrality Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. We show that the Pearson correlation coefficient $c(v_{2},v_{3})$ and $c(v_{3},v_{4})$ can be used as an EoS meter. We found $\sim 10\%$ difference in $c(v_{2},v_{3})$ and $c(v_{3},v_{4})$ for the two different EoSs for $20\%-30\%$ collision centrality irrespective of the initial condition used. The same observable was shown to be quite insensitive to the initial state fluctuation and/or shear viscosity of the medium in a previous study by Niemi et al. This indicates that these observables can be used to gain information about the QCD EoS from experimental data. In addition to that, we also found $\sim 15\% -30\%$ difference (depending on the model parameters and centrality of the collisions) in $c(\epsilon_{n}, v_{n})$ for $n=2-4$ for the two different EoSs. These observations may be attributed to very different evolutionary dynamics of the system for the two different EoS.

Glauber

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Functional characterization of an inducible bidirectional promoter from Fusarium oxysporum f. sp. cubense

Scientific Reports (2020)

Ashutosh Dash Vartika Gurdaswani Jacinta S. D’Souza Siddhesh B. Ghag

Abstract Bidirectional promoters (BDPs) are regulatory DNA sequences (~1000 bp long) intervening two genes arranged on opposite strands with their 5′ ends in close proximity. These genes are mostly co-expressed; but, instances of anti-correlation and independent transcription have been observed. In fungal systems, BDPs have shown to provide an improved genetic circuit by assembling and regulating transcription of different genes of a common metabolic pathway. We have identified an intergenic region (1063 bp) from the genome of Fusarium oxysporum f. sp. cubense ( Foc ), a banana root pathogen. This intergenic region regulates the expression of a gene pair required for the breakdown of hemicellulose. For characterization, it was cloned into pCSN44 vector backbone between two reporter genes, namely β-glucuronidase (GUS) and enhanced green fluorescent protein (EGFP). The newly formed vector was transformed into Foc and tested for its bidirectional expression activity. Using histochemical staining and fluorescence microscopy, the kinetics for both, GUS and EGFP expression were tested under different growth conditions respectively. The activity was differentially regulated by inducers such as xylan, arabinogalactan and pectin. This is the first report on the isolation of the intergenic region with inducible bidirectional promoter activity from Fusarium . Characterization of such BDPs will find applications in genetic engineering, metabolic engineering and synthetic biology using fungal systems.

Intergenic region

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10.1038/s41598-020-59159-0

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Thermodynamics of a Gas of Hadrons with Interaction Using S-Matrix Formalism

Springer proceedings in physics (2021)

Ashutosh Dash Subhasis Samanta B. Mohanty

Virial expansion

Formalism (music)

10.1007/978-981-33-4408-2_84

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Charged participants and their electromagnetic fields in an expanding fluid

Physics Letters B (2023)

Ashutosh Dash Ankit Kumar Panda

We investigate the space-time dependence of electromagnetic fields produced by charged participants in an expanding fluid. To address this problem, we need to solve the Maxwell's equations coupled to the hydrodynamics conservation equation, specifically the relativistic magnetohydrodynamics (RMHD) equations, since the charged participants move with the flow. To gain analytical insight, we approximate the problem by solving the equations in a fixed background Bjorken flow, onto which we solve Maxwell's equations. The dynamical electromagnetic fields interact with the fluid's kinematic quantities such as the shear tensor and the expansion scalar, leading to additional non-trivial coupling. We use mode decomposition of Green's function to solve the resulting non-linear coupled wave equations. We then use this function to calculate the electromagnetic field for two test cases: a point source and a transverse charge distribution. The results show that the resulting magnetic field vanishes at very early times, grows, and eventually falls at later times.

Electromagnetic tensor

10.1016/j.physletb.2023.138342

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Genome-wide in silico characterization and stress induced expression analysis of BcL-2 associated athanogene (BAG) family in Musa spp.

Scientific Reports (2022)

Ashutosh Dash Siddhesh B. Ghag

Abstract Programmed cell death (PCD) is a genetically controlled process for the selective removal of damaged cells. Though understanding about plant PCD has improved over years, the mechanisms are yet to be fully deciphered. Among the several molecular players of PCD in plants, B cell lymphoma 2 (Bcl-2)-associated athanogene (BAG) family of co-chaperones are evolutionary conserved and regulate cell death, growth and development. In this study, we performed a genome-wide in silico analysis of the MusaBAG gene family in a globally important fruit crop banana. Thirteen MusaBAG genes were identified, out of which MusaBAG1 , 7 and 8 genes were found to have multiple copies. MusaBAG genes were distributed on seven out of 11 chromosomes in banana. Except for one paralog of MusaBAG8 all the other 12 proteins have characteristic BAG domain. MusaBAG1, 2 and 4 have an additional ubiquitin-like domain whereas MusaBAG5-8 have a calmodulin binding motif. Most of the MusaBAG proteins were predicted to be localized in the nucleus and mitochondria or chloroplast. The in silico cis -regulatory element analysis suggested regulation associated with photoperiodic control, abiotic and biotic stress. The phylogenetic analysis revealed 2 major clusters. Digital gene expression analysis and quantitative real-time RT-PCR depicted the differential expression pattern of MusaBAG genes under abiotic and biotic stress conditions. Further studies are warranted to uncover the role of each of these proteins in growth, PCD and stress responses so as to explore them as candidate genes for engineering transgenic banana plants with improved agronomic traits.

Biotic stress

10.1038/s41598-021-04707-5

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Transport coefficients for multicomponent gas of hadrons using Chapman-Enskog method

Physical review. D/Physical review. D. (2019)

Ashutosh Dash Subhasis Samanta B. Mohanty

The transport coefficients of a multicomponent hadronic gas at zero and nonzero baryon chemical potential are calculated using the Chapman-Enskog method. The calculations are done within the framework of an $S$-matrix based interacting hadron resonance gas model. In this model, the phase shifts and cross sections are calculated using $K$-matrix formalism and where required, by parametrizing the experimental phase shifts. Using the energy dependence of the cross section, we find the temperature dependence of various transport coefficients such as shear viscosity, bulk viscosity, heat conductivity, and diffusion coefficient. We finally compare our results regarding various transport coefficients with previous results in the literature.

Formalism (music)

10.1103/physrevd.100.014025

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Testing gravitational self-interaction via matter-wave interferometry

Physical review. A/Physical review, A (2022)

Sourav Kesharee Sahoo Ashutosh Dash Radhika Vathsan Tabish Qureshi

The Schr\"odinger-Newton equation has frequently been studied as a nonlinear modification of the Schr\"odinger equation incorporating gravitational self-interaction. However, there is no evidence yet as to whether nature actually behaves this way. This work investigates a possible way to experimentally test gravitational self-interaction. The effect of self-gravity on the interference of massive particles is studied by numerically solving the Schr\"odinger-Newton equation for a particle passing through a double-slit. The results show that the presence of gravitational self-interaction has an effect on the fringe width of the interference that can be tested in matter-wave interferometry experiments. Notably, this approach can distinguish between gravitational self-interaction and environment-induced decoherence, as the latter does not affect the fringe width. This result will also provide a way to test if gravity requires to be quantized on the scale of ordinary quantum mechanics.

Test particle

Double-slit experiment

Matter wave

10.1103/physreva.106.012215

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Causality and stability in relativistic viscous magneto-fluid dynamics

arXiv (Cornell University) (2020)

Rajesh Biswas Ashutosh Dash Najmul Haque Shi Pu Victor Roy

We investigate the causality and the stability of the relativistic viscous magneto-hydrodynamics in the framework of the Israel-Stewart (IS) second-order theory, and also within a modified IS theory which incorporates the effect of magnetic fields in the relaxation equations of the viscous stress. We compute the dispersion relation by perturbing the fluid variables around their equilibrium values. In the ideal magnetohydrodynamics limit, the linear dispersion relation yields the well-known propagating modes: the Alfv\'en and the magneto-sonic modes. In the presence of bulk viscous pressure, the causality bound is found to be independent of the magnitude of the magnetic field. The same bound also remains true, when we take the full non-linear form of the equation using the method of characteristics. In the presence of shear viscous pressure, the causality bound is independent of the magnitude of the magnetic field for the two magneto-sonic modes. The causality bound for the shear-Alfv\'en modes, however, depends both on the magnitude and the direction of the propagation. For modified IS theory in the presence of shear viscosity, new non-hydrodynamic modes emerge but the asymptotic causality condition is the same as that of IS. In summary, although the magnetic field does influence the wave propagation in the fluid, the study of the stability and asymptotic causality conditions in the fluid rest frame shows that the fluid remains stable and causal given that they obey certain asymptotic causality condition.

Causality

Dispersion relation

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Metric anisotropies and emergent anisotropic hydrodynamics

Physical review. D/Physical review. D. (2018)

Ashutosh Dash Amaresh Jaiswal

Expansion of a locally equilibrated fluid is considered in an anisotropic space-time given by Bianchi type I metric. Starting from isotropic equilibrium phase-space distribution function in the local rest frame, we obtain expressions for components of the energy-momentum tensor and conserved current, such as number density, energy density and pressure components. In the case of an axis-symmetric Bianchi type I metric, we show that they are identical to that obtained within the setup of anisotropic hydrodynamics. We further consider the case when Bianchi type I metric is a vacuum solution of Einstein equation: the Kasner metric. For axis-symmetric Kasner metric, we discuss the implications of our results in the context of anisotropic hydrodynamics.

Rest frame

Metric tensor

Einstein field equations

Perfect fluid

10.1103/physrevd.97.104005

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