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Arnab Roy

Publications and source records attributed to Arnab Roy.

At least 55 records · Page 3Linked to original sources
arXiv2023

Hunting ewinos and a light scalar of $Z_3$-NMSSM with a bino-like dark matter in top squark decays at the LHC

We study the prospects of a simultaneous hunt at the Large Hadron Collider (LHC) of relatively light electroweakinos and a singlet-like scalar of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model ($Z_3$-NMSSM) in the cascade decays of not so heavy ($\lesssim 1.5$ TeV) top squarks that are produced in pairs at the LHC which characteristically involve the singlet-like states. We work in a scenario where the lightest (next-to-lightest) SUSY particle is bino (singlino)-like with a mass below 100 GeV ($\gtrsim 100$ GeV), whereas a pair of immediately heavier neutralinos and the lighter chargino are higgsino-like with masses in the range $\sim 500$ GeV -- 1 TeV. Further, the singlet-like scalar present in the spectrum provides a funnel for a rapid enough mutual annihilation of the LSP thus making the latter meet the experimental upper bound on its relic abundance. The scenario is motivated by its ability to offer a bino-like dark matter with such a mass unlike what is now disfavored in the MSSM while avoiding the stringent lower bounds from the LHC experiments on the masses of these involved particles and still remaining reasonably `natural'. We find that while a usual cut-based analysis (CBA) on LHC data worth 300 $\text{fb}^{-1}$ would be unable to discover such excitations, a multivariate analysis (MVA) can be reasonably sensitive to higgsino-like electroweakinos having masses $\gtrsim 650$ GeV when the lighter top squark has a mass $\gtrsim 1$ TeV. On the other hand, with 3000 $\text{fb}^{-1}$ of data these masses become accessible in a CBA while even an MVA on such a data set is unlikely to find these electroweakinos with masses around 1 TeV when the mass of the lighter top squark hits $\sim 1.5$ TeV.

hep-ph↗
arXiv2023

Nonlinear theory remedies the lack of invertibility in time periodic fluid flows

This paper provides a framework to strong time periodic solutions of quasilinear evolution equations. The novelty of this approach is that zero is allowed to be a spectral value of the underlying linearized operator. This approach is then applied to time periodic problems associated to the Navier-Stokes equations, generalized Newtonian fluids, quasilinear reaction-diffusion systems as well as to magneto-hydrodynamics.

math.AP↗
arXiv2023

Global existence of Weak Solutions for a model of nematic liquid crystal-colloidal interactions

In this paper we study a mathematical model describing the movement of a colloidal particle in a fixed, bounded three dimensional container filled with a nematic liquid crystal fluid. The motion of the fluid is governed by the Beris-Edwards model for nematohydrodynamics equations, which couples the incompressible Navier-Stokes equations with a parabolic system. The dynamics of colloidal particle within the nematic liquid crystal is described by the conservation laws of linear and angular momentum. We prove the existence of global weak solutions for the coupled system.

math.AP↗
arXiv2023

Exploring SMEFT operators in the tHq production at the LHC

We study the top-quark production along with a Higgs boson and a jet (tHq) at the LHC experiment within the framework of the Standard Model Effective Field Theory (SMEFT). A strategy is developed to constrain the Wilson Coefficients (WC) corresponding to the associated SMEFT operators using the latest LHC measurements. The best-fit values of these WCs are presented. Finally, we demonstrate the feasibility of finding the effects of these operators on various kinematical observables of the tHq process at the LHC. We find that for a set of best-fitted values of the considered WCs, the excess of signal over the backgrounds can be achieved with a reasonable significance at the center of mass energy $\sqrt{s}=13$ TeV and for integrated luminosity options ${\cal L}=$300 $\rm fb^{-1}$ and 3000 $\rm fb^{-1}$.

hep-ph↗
arXiv2023

Interpolation by Different Types of Quantum Channels Using Conic Programs

We have found conic programs for getting different types of quantum channels as outputs of interpolation problems. Afterwards, we have generalized our results for getting channels that belong to a convex set as outputs of the interpolation problem. We show the existence of an Entanglement breaking channel for orthogonal sets of input and output matrices.

quant-ph↗
arXiv2023

Wellposedness of Boussinesq system

In this paper, we consider the viscous, incompressible, nonlinear Boussinesq system in two and three spatial dimension. We study the existence and regularity of solutions to the Boussinesq system with nonhomogeneous boundary conditions for which the normal component for the velocity is not necessary equal to zero. We establish the existence of global weak solutions to the three-dimensional instationary nonlinear Boussinesq system but without any smallness assumption on the initial and boundary conditions.

math.AP↗
arXiv2023

Arion: Arithmetization-Oriented Permutation and Hashing from Generalized Triangular Dynamical Systems

In this paper we propose the (keyed) permutation Arion and the hash function ArionHash over $\mathbb{F}_p$ for odd and particularly large primes. The design of Arion is based on the newly introduced Generalized Triangular Dynamical System (GTDS), which provides a new algebraic framework for constructing (keyed) permutation using polynomials over a finite field. At round level Arion is the first design which is instantiated using the new GTDS. We provide extensive security analysis of our construction including algebraic cryptanalysis (e.g. interpolation and Gröbner basis attacks) that are particularly decisive in assessing the security of permutations and hash functions over $\mathbb{F}_p$. From an application perspective, ArionHash aims for efficient implementation in zkSNARK protocols and Zero-Knowledge proof systems. For this purpose, we exploit that CCZ-equivalence of graphs can lead to a more efficient implementation of Arithmetization-Oriented primitives. We compare the efficiency of ArionHash in R1CS and Plonk settings with other hash functions such as Poseidon, Anemoi and Griffin. For demonstrating the practical efficiency of ArionHash we implemented it with the zkSNARK libraries libsnark and Dusk Network Plonk. Our result shows that ArionHash is significantly faster than Poseidon - a hash function designed for zero-knowledge proof systems. We also found that an aggressive version of ArionHash is considerably faster than Anemoi and Griffin in a practical zkSNARK setting.

cs.CR↗
arXiv2023

Generalized Triangular Dynamical System: An Algebraic System for Constructing Cryptographic Permutations over Finite Fields

In recent years a new class of symmetric-key primitives over $\mathbb{F}_p$ that are essential to Multi-Party Computation and Zero-Knowledge Proofs based protocols have emerged. Towards improving the efficiency of such primitives, a number of new block ciphers and hash functions over $\mathbb{F}_p$ were proposed. These new primitives also showed that following alternative design strategies to the classical Substitution-Permutation Network (SPN) and Feistel Networks leads to more efficient cipher and hash function designs over $\mathbb{F}_p$ specifically for large odd primes $p$. In view of these efforts, in this work we build an \emph{algebraic framework} that allows the systematic exploration of viable and efficient design strategies for constructing symmetric-key (iterative) permutations over $\mathbb{F}_p$. We first identify iterative polynomial dynamical systems over finite fields as the central building block of almost all block cipher design strategies. We propose a generalized triangular polynomial dynamical system (GTDS), and based on the GTDS we provide a generic definition of an iterative (keyed) permutation over $\mathbb{F}_p^n$. Our GTDS-based generic definition is able to describe the three most well-known design strategies, namely SPNs, Feistel networks and Lai--Massey. Consequently, the block ciphers that are constructed following these design strategies can also be instantiated from our generic definition. Moreover, we find that the recently proposed \texttt{Griffin} design, which neither follows the Feistel nor the SPN design, can be described using the generic GTDS-based definition. We also show that a new generalized Lai--Massey construction can be instantiated from the GTDS-based definition. We further provide generic analysis of the GTDS including an upper bound on the differential uniformity and the correlation.

cs.CR↗
arXiv2023

Transoceanic migration of dragonflies and branched optimal route networks

The intriguing annual migration of the dragonfly species, Pantala flavescens was reported almost a century ago (Fraser 1924). The multi-generational, transoceanic migration circuit spanning from India to Africa is an astonishing feat for an inches-long insect. Wind, precipitation, fuel, breeding, and life cycle affect the migration, yet understanding of their collective role in the migration remains elusive. We identify the transoceanic migration route by imposing a time constraint emerging from energetics on Djikstra's path-planning algorithm. Energetics calculations reveal a Pantala flavescens can endure 90 hours of steady flight at 4.5m/s. We incorporate active wind compensation in Djikstra's algorithm to compute the migration route from years 2002 to 2007. The prevailing winds play a pivotal role; a direct crossing of the Indian Ocean from Africa to India is feasible with the Somali Jet, whereas the return requires stopovers in Maldives and Seychelles. The migration timing, identified using monthly-successful trajectories, life cycle, and precipitation data, corroborates reported observations. Finally, our timely sighting in Cherrapunji, India (25.2N 91.7E) and a branched network hypothesis connect the likely origin of the migration in North-Eastern India with Pantala flavescens's arrival in South-Eastern India with the retreating monsoons; a clue to their extensive global dispersal.

physics.bio-ph↗
arXiv2022

On the motion of a large number of small rigid bodies in a viscous incompressible fluid

We consider the motion of $N$ rigid bodies -- compact sets $(\mathcal{S}^1_\varepsilon, \cdots, \mathcal{S}^N_\varepsilon )_{\varepsilon > 0}$ -- immersed in a viscous incompressible fluid contained in a domain in the Euclidean space $\mathbb{R}^d$, $d=2,3$. We show the fluid flow is not influenced by the presence of the infinitely many bodies in the asymptotic limit $\varepsilon \to 0$ and $N=N(\varepsilon)\rightarrow\infty$ as soon as \[ {\rm diam}[\mathcal{S}^i_\varepsilon ] \to 0 \ \mbox{as}\ \varepsilon \to 0 ,\ i=1,\cdots, N(\varepsilon). \] The result depends solely on the geometry of the bodies and is independent of their mass densities. Collisions are allowed and the initial data are arbitrary with finite energy.

math.AP↗
arXiv2022

Exploring SMEFT operators through single top-quark production associated with the Higgs boson at the LHC

The Standard Model effective field theory (SMEFT) provides a general framework to include the dynamics of the beyond standard model physics residing at a certain higher energy scale $Λ$. We study the top-quark production along with a Higgs boson and a jet (tHq) at the LHC experiment within the framework of the SMEFT. First, identifying the relevant sensitive dimension-6 SMEFT operators, a strategy is developed to constrain the Wilson Coefficients (WC) corresponding to these associated SMEFT operators using the latest LHC measurements, providing a complementary way to the global-fit approach. The best-fit values of these WCs are presented. Finally, we discuss the discovery potential of the signatures of those operators. We find that a discoverable excess due to SMEFT effects can be observed in the tHq process at the LHC with the center of mass energy $\sqrt{s}=13$ TeV and integrated luminosity options ${\cal L}=$300 $\rm fb^{-1}$ and 3000 $\rm fb^{-1}$.

hep-ph↗
arXiv2022

Vandermonde Constrained Tensor Decomposition for Hybrid Beamforming in Multi-Carrier MIMO Systems

Hybrid beamforming has evolved as a promising technology that offers the balance between system performance and design complexity in mmWave MIMO systems. Existing hybrid beamforming methods either impose unit-modulus constraints or a codebook constraint on the analog precoders/combiners, which in turn results in a performance-overhead tradeoff. This paper puts forth a tensor framework to handle the wideband hybrid beamforming problem, with Vandermonde constraints on the analog precoders/combiners. The proposed method strikes the balance between performance, overhead and complexity. Numerical results on a 3GPP link-level test bench reveal the efficacy of the proposed approach relative to the codebook-based method while attaining the same feedback overhead. Moreover, the proposed method is shown to achieve comparable performance to the unit-modulus approaches, with substantial reductions in overhead.

eess.SP↗
arXiv2022

On the motion of a small rigid body in a viscous compressible fluid

We consider the motion of a small rigid object immersed in a viscous compressible fluid in the 3-dimensional Eucleidean space. Assuming the object is a ball of a small radius $\varepsilon$ we show that the behavior of the fluid is not influenced by the object in the asymptotic limit $\varepsilon \to 0$. The result holds for the isentropic pressure law $p(\varrho) = a \varrho^γ$ for any $γ> \frac{3}{2}$ under mild assumptions concerning the rigid body density. In particular, the latter may be bounded as soon as $γ> 3$. The proof uses a new method of construction of the test functions in the weak formulation of the problem, and, in particular, a new form of the so-called Bogovskii operator.

math.AP↗
arXiv2022

On the motion of a nearly incompressible viscous fluid containing a small rigid body

We consider the motion of a compressible viscous fluid containing a moving rigid body confined to a planar domain $Ω\subset R^2$. The main result states that the influence of the body on the fluid is negligible if (i) the diameter of the body is small and (ii) the fluid is nearly incompressible (the low Mach number regime). The specific shape of the body as well as the boundary conditions on the fluid--body interface are irrelevant and collisions with the boundary $\partial Ω$ are allowed. The rigid body motion may be enforced externally or governed solely by its interaction with the fluid.

math.AP↗
arXiv2022

Enhancement of Superconductivity upon reduction of carrier density in proximitized graphene

The superconducting transition temperature (Tc) of a single layer graphene coupled to an Indium oxide (InO) film, a low carrier-density superconductor, is found to increase with decreasing carrier density and is largest close to the average charge neutrality point in graphene. Such an effect is very surprising in conventional BCS superconductors. We study this phenomenon both experimentally and theoretically. Our analysis suggests that the InO film induces random electron and hole-doped puddles in the graphene. The Josephson effect across these regions of opposite polarity enhances the Josephson coupling between the superconducting clusters in InO, along with the overall Tc of the bilayer heterostructure. This enhancement is most effective when the chemical potential of the system is tuned between the charge neutrality points of the electron and hole-doped regions.

cond-mat.supr-con↗
arXiv2022

Existence of a weak solution to a nonlinear fluid-structure interaction problem with heat exchange

In this paper, we study a nonlinear interaction problem between a thermoelastic shell and a heat-conducting fluid. The shell is governed by linear thermoelasticity equations and encompasses a time-dependent domain which is filled with a fluid governed by the full Navier-Stokes-Fourier system. The fluid and the shell are fully coupled, giving rise to a novel nonlinear moving boundary fluid-structure interaction problem involving heat exchange. The existence of a weak solution is obtained by combining three approximation techniques -- decoupling, penalization and domain extension. This approximation scheme allows us to use the methods already developed for fluids on moving domains, thus drastically simplifying the analysis at hand.

math.AP↗
arXiv2022

Binary matrix factorization on special purpose hardware

Many fundamental problems in data mining can be reduced to one or more NP-hard combinatorial optimization problems. Recent advances in novel technologies such as quantum and quantum-inspired hardware promise a substantial speedup for solving these problems compared to when using general purpose computers but often require the problem to be modeled in a special form, such as an Ising or quadratic unconstrained binary optimization (QUBO) model, in order to take advantage of these devices. In this work, we focus on the important binary matrix factorization (BMF) problem which has many applications in data mining. We propose two QUBO formulations for BMF. We show how clustering constraints can easily be incorporated into these formulations. The special purpose hardware we consider is limited in the number of variables it can handle which presents a challenge when factorizing large matrices. We propose a sampling based approach to overcome this challenge, allowing us to factorize large rectangular matrices. In addition to these methods, we also propose a simple baseline algorithm which outperforms our more sophisticated methods in a few situations. We run experiments on the Fujitsu Digital Annealer, a quantum-inspired complementary metal-oxide-semiconductor (CMOS) annealer, on both synthetic and real data, including gene expression data. These experiments show that our approach is able to produce more accurate BMFs than competing methods.

cs.LG↗