arXiv subjects

A. Sengupta

Publications and source records attributed to A. Sengupta.

30 records · Page 2Linked to original sources

arXiv2022

Bayesian analysis of QGP jet transport using multi-scale modeling applied to inclusive hadron and reconstructed jet data

The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitative comparison of model calculations and data. The multi-stage framework incorporates multiple models to cover a broad range in scale of the in-medium parton shower evolution, with dynamical choice of model that depends on the current virtuality or energy of the parton. We will discuss the physics of the multi-stage modeling, and then present a new Bayesian analysis incorporating it. This analysis extends the recently published JETSCAPE determination of the jet transport parameter $\hat{q}$ that was based solely on inclusive hadron suppression data, by incorporating reconstructed jet measurements of quenching. We explore the functional dependence of jet transport coefficients on QGP temperature and jet energy and virtuality, and report the consistency and tensions found for current jet quenching modeling with hadron and reconstructed jet data over a wide range in kinematics and $\sqrt{s_{\text{NN}}}$. This analysis represents the next step in the program of comprehensive analysis of jet quenching phenomenology and its constraint of properties of the QGP.

hep-ph↗

arXiv2021

First principles design of 2 dimensional Nickel dichalcogenide Janus materials NiXY (X,Y=S,Se,Te)

In this work, we propose novel two-dimensional (2D) Janus Ni dichalcogenide materials and explore their feasibility, stability and evaluate their electronic and optical properties with ab-initio calculations. Three unique Janus materials, namely NiSSe, NiSTe and NiSeTe, based on the 2H hexagonal polytype of NiS2, NiSe2 and NiTe2 were proposed. Density functional theory (DFT) calculations, show that among the three proposed NiXY Janus 2D materials, NiSSe had the best energetic and dynamical stability. GGA PBE calculations showed NiSSe to have a semi-metallic bandstructure with the Ni-Se interaction having a dominant role in the band profile near the Fermi energy. Electron localization function (ELF) and total potential plots show a distinguishable asymmetry in terms of valence electron localization and distribution between the S and Se atoms in 2D NiSSe. The presence of large amount of electron gas like feature in the ELF around the chalcogen atoms also indicates their importance in the conduction properties. Optical properties calculated with random phase approximation (RPA) show the 2D NiSSe to have broad spectrum optical response with significant peaks lying in each of the infra-red, visible and the ultraviolet range of the spectra.

cond-mat.mtrl-sci↗

arXiv2016

Colloids Exposed to Random Potential Energy Landscapes: from Particle Number Density to Particle-Potential and Particle-Particle Interactions

Colloidal particles were exposed to a random potential energy landscape (rPEL) that has been created optically via a speckle pattern. The mean particle density as well as the potential roughness, i.e. the disorder strength, were varied. The local probability density of the particles as well as its main characteristics were determined. For the first time, the disorder-averaged pair density correlation function and an analogue of the Edwards-Anderson order parameter, which quantifies the correlation of the mean local density among disorder realisations, were measured experimentally and shown to be consistent with replica liquid state theory results.

cond-mat.soft↗

arXiv2016

Performance Analysis of uniaxially strained Monolayer Black Phosphorus and Blue Phosphorus n-MOSFET and p-MOSFET

In this work, we present a computational study on the possibility of strain engineering in monolayer Black Phosphorus (black P) and Blue Phosphorus (blue P) based MOSFETs. The material properties like band structure, carrier effective masses, carrier densities at band extrema are evaluated using Generalized Gradient Approximation (GGA) in Density Functional Theory (DFT).Thereafter self-consistent Non-Equilibrium Greens Function (NEGF) simulations are carried out to study the device performance metrics (such as output characteristics, ON currents, transconductance etc.) of such strained black P and blue P based MOSFETs. Our simulations show that carrier effective masses in blue P are more sensitive to strain applied in both zigzag and armchair directions. Blue P is more responsive in strain engineering for n-MOS and p-MOS. Except for black P based FETs with strain in armchair direction, overall the blue P (black P) n-MOSFET (p-MOSFET) show moderate to significant improvement in performance with tensile (compressive) strain in the transport directions.

cond-mat.mtrl-sci↗

arXiv2015

Stacking dependence of carrier transport properties in multilayered black phosphorous

We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with Generalized Gradient Approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the Meta-Generalized Gradient Approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium Greens function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gap, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous.

cond-mat.mtrl-sci↗

arXiv2015

Multi-Beam RF Aperture Using Multiplierless FFT Approximation

Multiple independent radio frequency (RF) beams find applications in communications, radio astronomy, radar, and microwave imaging. An $N$-point FFT applied spatially across an array of receiver antennas provides $N$-independent RF beams at $\frac{N}{2}\log_2N$ multiplier complexity. Here, a low-complexity multiplierless approximation for the 8-point FFT is presented for RF beamforming, using only 26 additions. The algorithm provides eight beams that closely resemble the antenna array patterns of the traditional FFT-based beamformer albeit without using multipliers. The proposed FFT-like algorithm is useful for low-power RF multi-beam receivers; being synthesized in 45 nm CMOS technology at 1.1 V supply, and verified on-chip using a Xilinx Virtex-6 Lx240T FPGA device. The CMOS simulation and FPGA implementation indicate bandwidths of 588 MHz and 369 MHz, respectively, for each of the independent receive-mode RF beams.

stat.ME↗

arXiv2012

Adventures Beyond Reductionism: The Wondrous Manifesto of Holism

"If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous successive, slight modifications, my theory would absolutely break down". Can Darwinian random mutations and selection generate biological complexity and holism? In this paper we argue that the "wonderful but not enough" tools of linear reductionism cannot lead to chaos and hence to complexity and holism, but with ChaNoXity this seems indeed plausible, even likely. Based on the Pump-Engine realism of mutually interacting supply and demand --- demand institutes supply that fuels demand --- we demonstrate that the "supply" of symmetry breaking Darwinian genetic variation, in direct conflict with the symmetry inducing "demand" of natural selection, defines the antagonistic arrows of the real and negative worlds. Working in this competitively collaborating nonlinear mode, these opposites generate the homeostasy of holistic life. Protein folding, mitosis, meiosis, hydrophobicity and other ingredients have their respective expressions in this paradigm; nucleotide substitution, gene duplication-divergence, HGT, stress-induced mutations, antibiotic resistance, Lamarckism would appear to fit in naturally in this complexity paradigm defined through emergence of novelty and self-organization. With obvious departures from current reductionism, this can have far reaching implications in the Darwinian and nano medicine of genetic diseases and disorders. Our goal is to chart a roadmap of adventure beyond (neo)-Darwinian reductionism.

physics.gen-ph↗

arXiv2010

Gravitational Collapse, Negative World and Complex Holism

Building on the engine-pump paradigm of ChaNoXity, this paper argues that complex holism - as the competitive homeostasis of dispersion and concentration - is the operating mode of Nature. Specifically, we show that the negative world \mathfrak{W} is a gravitationally collapsed black hole that was formed at big-bang time t=0 as the pair (W,\mathfrak{W}), with W a real world, and gravity the unique expression of the maximal multifunctional nonlinearity of the negative world \mathfrak{W} in the functional reality of W. The temperature of a gravitationally collapsed system does enjoy the relationship T\propto1/r with its radius, but the entropy follows the usual volumetric alignment with microstates, reducing to the surface approximation only at small r. It is not clear if quantum non-locality is merely a linear manifestation of complex holism, with the interaction of quantum gates in quantum entanglements resulting in distinctive features from the self-evolved structures of complex holism remaining an open question for further investigation

physics.gen-ph↗

arXiv2004

ChaNoXity: The Nonlinear Dynamics of Nature

In this paper we employ the topological-multifuncoctional mathematical language and techniques of non-injective illposedness developed earlier to formulate a notion of ChaNoXity -- Chaos-Nonlinearity-Complexity -- in describing the specifically nonlinear dynamical evolutionary processes of Nature. Non-bijective ill-posedness is the natural mode of expression for chanoxity that aims to focus on the nonlinear interactions generating dynamical evolution of real irreversible processes. The basic dynamics is considered to take place in a matter-antimatter kitchen space of Nature that is inaccessible to both the functional matter and multifunctional antimatter components. These component spaces are distinguished by opposing evolutionary directional arrows. Dynamical equilibrium is considered to be represented by such competitively collaborating stasis states of the matter-antimatter constituents of Nature.

nlin.AO↗

arXiv2004

Toward a Theory of Chaos

This paper formulates a new approach to the study of chaos in discrete dynamical systems based on the notions of inverse ill-posed problems, set-valued mappings, generalized and multivalued inverses, graphical convergence of a net of functions in an extended multifunction space, and the topological theory of convergence. Order, chaos, and complexity are described as distinct components of this unified mathematical structure that can be viewed as an application of the theory of convergence in topological spaces to increasingly nonlinear mappings, with the boundary between order and complexity in the topology of graphical convergence being the region in Multi(X) that is susceptible to chaos. The paper uses results from the discretized spectral approximation in neutron transport theory and concludes that the numerically exact results obtained by this approximation of the Case singular eigenfunction solution is due to the graphical convergence of the Poisson and conjugate Poisson kernels to the Dirac delta and the principal value multifunctions respectively. In Multi(X), the continuous spectrum is shown to reduce to a point spectrum, and we introduce a notion of latent chaotic states to interpret superposition over generalized eigenfunctions. Along with these latent states, spectral theory of nonlinear operators is used to conclude that nature supports complexity to attain efficiently a multiplicity of states that otherwise would remain unavailable to it.

nlin.CD↗

arXiv2003

Fock spaces corresponding to positive definite linear transformations

Suppose $A$ is a positive real linear transformation on a finite dimensional complex inner product space $V$. The reproducing kernel for the Fock space of square integrable holomorphic functions on $V$ relative to the Gaussian measure $dμ_A(z)=\frac {\sqrt {\det A}} {π^n}e^{-{\rm Re}< Az,z>} dz$ is described in terms of the holomorphic--antiholomorphic decomposition of the linear operator $A$. Moreover, if $A$ commutes with a conjugation on $V$, then a restriction mapping to the real vectors in $V$ is polarized to obtain a Segal--Bargmann transform, which we also study in the Gaussian-measure setting.

math.FA↗

arXiv1994

Solution of the two impurity, two channel Kondo Model

We solve the two-impurity two-channel Kondo model using a combination of conformal invariance and bosonisation techniques. The odd-even symmetric case is analysed in detail. The RKKY interaction turns out to be exactly marginal, resulting in a line of non-Fermi liquid fixed points. Explicit formulae are given for the critical exponents and for the finite-size spectrum, which depend continuously on a single parameter. The marginal line spans a range of values of the RKKY coupling $I$ which goes from the infinitely strong ferromagnetic point $I=-\infty$ (associated with a 4-channel spin-1 Kondo model) to a finite antiferromagnetic critical value $I_c>0$ beyond which a Fermi liquid is recovered. We also find that, when the odd-even symmetry is broken, the marginal line is unstable for ferromagnetic $I$, while for antiferromagnetic $I$ it extends into a manifold of fixed points.

cond-mat↗