800 research outputs found
Correlation and entanglement spreading in nested spin chains
No full textThe past few years have witnessed the development of a comprehensive theory to describe integrable systems out of equilibrium, in which the Bethe ansatz formalism has been tailored to address specific problems arising in this context. While most of the work initially focused on the study of prototypical models such as the well-known Heisenberg chain, many theoretical results have been recently extended to a class of more complicated nested integrable systems, displaying different species of quasiparticles. Still, in the simplest context of quantum quenches, the vast majority of theoretical predictions have been numerically verified only in systems with an elementary Bethe ansatz description. In this work, we fill this gap and present a direct numerical test of some results presented in the recent literature for nested systems, focusing in particular on the Lai–Sutherland model. Using time-dependent density matrix renormalization group and exact diagonalization methods, we compute the spreading of both correlation functions and entanglement entropy after a quench from a simple class of product initial states. This allows us to test the validity of the nested version of a conjectured formula, based on the quasiparticle picture, for the growth of the entanglement entropy, and the Bethe ansatz predictions for the 'light-cone' velocity of correlation functions
Correlation and entanglement spreading in nested spin chains
No full textThe past few years have witnessed the development of a comprehensive theory to describe integrable systems out of equilibrium, in which the Bethe ansatz formalism has been tailored to address specific problems arising in this context. While most of the work initially focused on the study of prototypical models such as the well-known Heisenberg chain, many theoretical results have been recently extended to a class of more complicated nested integrable systems, displaying different species of quasiparticles. Still, in the simplest context of quantum quenches, the vast majority of theoretical predictions have been numerically verified only in systems with an elementary Bethe ansatz description. In this work, we fill this gap and present a direct numerical test of some results presented in the recent literature for nested systems, focusing in particular on the Lai–Sutherland model. Using time-dependent density matrix renormalization group and exact diagonalization methods, we compute the spreading of both correlation functions and entanglement entropy after a quench from a simple class of product initial states. This allows us to test the validity of the nested version of a conjectured formula, based on the quasiparticle picture, for the growth of the entanglement entropy, and the Bethe ansatz predictions for the ‘light-cone’ velocity of correlation functions
Investment protection a must in India-UK FTA
No full textThe India-UK investment relationship is no more a one-way street. In 2020, the stock of foreign direct investment from India in the UK was £10.6 billion as against £14.9 billion from the UK in India
A priori and a posteriori analysis of the hybrid two-level large-eddy simulation method for high Reynolds number complex flows
No full textWe present a priori and a posteriori analysis of the assumptions and predictions of the hybrid two-level large-eddy simulation (TLS-LES) method for high Reynolds number complex flows. The TLS-LES methodology is a multi-scale framework for simulation of turbulent flows in complex configurations at practically relevant Reynolds number. It additively combines the two-level simulation (TLS) model with a conventional large-eddy simulation (LES) approach by employing a static or dynamic blending function. In the present study, first we analyze the model assumptions employed by the TLS model to obtain the small-scale solution necessary for closure of the large-scale equations. Afterward, we analyze the large-scale and small-scale solutions to assess the predictive ability of the multi-scale framework for specific turbulence physics such as role of forward and backscatter of energy and presence of co- and counter-gradient diffusion. To perform these investigations, we consider cases with increasing degree of geometrical complexity, namely, flow in a periodic channel, flow past a bump placed on the lower surface of the channel and flow past a finite-span NACA0015 airfoil
Criterion for the occurrence of many-body localization in the presence of a single-particle mobility edge
No full textNoninteracting fermions in one dimension can undergo a localization-delocalization transition in the presence of a quasiperiodic potential as a function of that potential. In the presence of interactions, this transition transforms into a many-body localization (MBL) transition. Recent studies have suggested that this type of transition can also occur in models with quasiperiodic potentials that possess single-particle mobility edges. Two such models were studied by Modak and Mukerjee Phys. Rev. Lett. 115, 230401 (2015)] but only one was found to exhibit an MBL transition in the presence of interactions while the other one did not. In this work we investigate the occurrence of MBL in the presence of weak interactions in five different models with single-particle mobility edges in one dimension with a view to obtaining a criterion for the same. We find that not all such models undergo a thermal-MBL phase transition in the presence of weak interactions. We propose a criterion to determine whether MBL is likely to occur in the presence of interaction based only on the properties of the noninteracting models. The relevant quantity epsilon is a measure of how localized the localized states are relative to how delocalized the delocalized states are in the noninteracting model. We also study various other features of the noninteracting models such as the divergence of the localization length at the mobility edge and the presence or absence of ``ergodicity'' and localization in their many-body eigenstates. However, we find that these features cannot be used to predict the occurrence of MBL upon the introduction of weak interactions
International Outsourcing Hurdles in Value-added Services
No full textPurpose: International Outsourcing has been traditionally looked upon as a low end cost effective servicing option to take advantage of the cost arbitrage that exists across countries. Of late, many outsourcing vendors have realized that the advantages of cost differentials that spurred a lot of the global outsourcing business in the past 20 years will disappear in the medium term. This paper provides a perspective about how much value addition, besides cost, traditional outsourcing vendors can provide and what may be the facilitator/ inhibitors of such activities. Approach: To substantiate the claim, a brief case describing the setting up of an offshore analytics operation is presented which gives a back drop to the challenges faced in relatively high end value creation processes in a remote outsourced environment. Findings/Claim: The author uses the case to develop a conceptual model of off shoring value –added services. The key dimensions that will determine the extent to which international outsourcing of high end services will take place are: 1) Expertise of the vendor, 2) Environmental Stability of the Outsourcing Domain, 3) Physical Barriers to outsourcing complex business processes such as, Communication Problems and Proximity issues, 4) Possibility of Knowledge Leakage from Outsourcing Domain and, 5) Cost Benefits of Outsourcing. Practical Implications: The author contends that conventional outsourcing vendors may find it difficult to acquire “Expert Power” and, set aside negative perceptions of “Environmental Stability” of their domain, in the pursuit to climb up the value chain in their client organizations. The validation of the proposed model is an opportunity for future research. Originality: This paper is one of the first to present a model that will govern the growth of international outsourcing opportunities in high end value-added processes.
Computational analysis of planar wings designed for optimum span-load
No full textA computational analysis of three span-optimized wings was conducted using an open-source CFD tool. Simulations were carried out at Rec = 450; 000 in a semi-spherical domain consisting of unstructured tetrahedra close to the wing surface and pyramids in the farfield region. Simulations were carried out in both steady state and semi-transient states to predict ow transition. A comparative study of different turbulence models revealed k-omega-SST and k - kL-omega to be the most suitable turbulence models for this study. The model accuracy was determined using validations with experimental data from a previous study. The required accuracy was achieved using the most appropriate mesh resolution for all three wing designs and second order discretization schemes. Computational results indicated different drag characteristics between the three span-load optimized wings at the design CL. The Viscous Optimized Wing produced the minimum drag while the Elliptic Wing produced the largest drag at design CL. The Inviscid Optimized Wing had the largest aspect ratio but still produced lesser drag when compared to the Elliptical Wing. Surface ow visualization indicated different ow transition characteristics for the three wings. These differences were attributed to the twist distributions specific to each wing. The Inviscid Optimized wing was observed to have largest laminar boundary-layer region at design angle of attack. Qualitative wake analysis indicated different wake characteristics for each wing, attributed to the different span-loads. The Elliptic Wing had the most aggressive wake roll-up. Much lesser wake roll-up was observed for the Inviscid and Viscous Optimized Wings. The largest wake cross-section was observed for the Elliptic Wing, while the smallest wake cross-section was observed for the Inviscid Optimized Wing.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-08-01The student, Prateek Ranjan, accepted the attached license on 2016-07-22 at 11:12.The student, Prateek Ranjan, submitted this Thesis for approval on 2016-07-22 at 11:25.This Thesis was approved for publication on 2016-07-22 at 16:28.DSpace SAF Submission Ingestion Package generated from Vireo submission #10076 on 2016-11-10 at 12:27:41Made available in DSpace on 2016-11-10T18:35:38Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-07-22Embargo set by: Seth Robbins for item 95403
Lift date: 2018-11-10T18:35:44Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 95403
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 95403
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 95403
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 95403 on 2018-11-11T10:15:32Z
Geometric quenches in quasi-disordered lattice system
No full textWhile global quantum quench has been extensively used in the literature to
understand the localization-delocalization transition for the one-dimensional
quantum spin chain, the effect of geometric quench (which corresponds to a
sudden change of the geometry of the chain) in the context of such transitions
is yet to be well understood. In this work, we investigate the effect of
geometric quench in the Aubry-Andre model, which supports
localization-delocalization transition even in one dimension. We study the
spreading of the entanglement and the site-occupation with time and find many
interesting features that can be used to characterize
localization-delocalization transition. We observe that geometric quench causes
a power-law type growth of the entanglement entropy in the delocalized phase in
contrast to the linear growth which is found in the global quench studies.
Remarkably, we also find that the saturation values in the Many-body localized
(MBL) phase obey Area law in contrast to the usual volume law which is a
signature feature of the MBL phase in the context of global quench.Comment: 6 pages, 8 figure
Finite size scaling in crossover among different random matrix ensembles in microscopic lattice models
No full textUsing numerical diagonalization we study the crossover among different random matrix ensembles (Poissonian, Gaussian orthogonal ensemble (GOE), Gaussian unitary ensemble (GUE) and Gaussian symplectic ensemble (GSE)) realized in two different microscopic models. The specific diagnostic tool used to study the crossovers is the level spacing distribution. The first model is a one-dimensional lattice model of interacting hard-core bosons (or equivalently spin 1/2 objects) and the other a higher dimensional model of non-interacting particles with disorder and spin-orbit coupling. We find that the perturbation causing the crossover among the different ensembles scales to zero with system size as a power law with an exponent that depends on the ensembles between which the crossover takes place. This exponent is independent of microscopic details of the perturbation. We also find that the crossover from the Poissonian ensemble to the other three is dominated by the Poissonian to GOE crossover which introduces level repulsion while the crossover from GOE to GUE or GOE to GSE associated with symmetry breaking introduces a subdominant contribution. We also conjecture that the exponent is dependent on whether the system contains interactions among the elementary degrees of freedom or not and is independent of the dimensionality of the system
Work extraction in an isolated quantum lattice system: Grand canonical and generalized Gibbs ensemble predictions
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