| 27841. |
- Banerjee, Souvik, et al.
(författare)
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Quenched coupling, entangled equilibria, and correlated composite operators : a tale of two O(N) models
- 2019
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :8
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Tidskriftsartikel (refereegranskat)abstract
- A macroscopic version of Einstein-Podolsky-Rosen entanglement is obtained by quenching a quadratic coupling between two O(N) vector models. A quench of the mixed vacuum produces an excited entangled state, reminiscent of purified thermal equilibrium, whose properties can be studied analytically in the free limit of the individual field theories. The decoupling of different wavelength modes in free field theory prevents true thermalisation but a more subtle difference is that the density operator obtained by a partial trace does not commute with the post-quench Hamiltonian. Generalized thermal behaviour is obtained at late times, in the limit of weak initial mixing or a smooth but rapid quench. More surprisingly, late-time correlation functions of composite operators in the post-quench free field theory share interesting properties with correlators in strongly coupled systems. We propose a holographic interpretation of our result.
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| 27842. |
- Banerjee, S, et al.
(författare)
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Spatiotemporal chaos and the dynamics of coupled Langmuir and ion-acoustic waves in plasmas
- 2010
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1539-3755 .- 1550-2376. ; 81:4
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Tidskriftsartikel (refereegranskat)abstract
- A simulation study is performed to investigate the dynamics of coupled Langmuir waves (LWs) and ion-acoustic waves (IAWs) in an unmagnetized plasma. The effects of dispersion due to charge separation and the density nonlinearity associated with the IAWs are considered to modify the properties of Langmuir solitons, as well as to model the dynamics of relatively large amplitude wave envelopes. It is found that the Langmuir wave electric field, indeed, increases by the effect of ion-wave nonlinearity (IWN). Use of a low-dimensional model, based on three Fourier modes, shows that a transition to temporal chaos is possible, when the length scale of the linearly excited modes is larger than that of the most unstable ones. The chaotic behaviors of the unstable modes are identified by the analysis of Lyapunov exponent spectra. The space-time evolution of the coupled LWs and IAWs shows that the IWN can cause the excitation of many unstable harmonic modes and can lead to strong IAW emission. This occurs when the initial wave field is relatively large or the length scale of IAWs is larger than the soliton characteristic size. Numerical simulation also reveals that many solitary patterns can be excited and generated through the modulational instability of unstable harmonic modes. As time goes on, these solitons are seen to appear in the spatially partial coherence state due to the free ion-acoustic radiation as well as in the state of spatiotemporal chaos due to collision and fusion in the stochastic motion. The latter results in the redistribution of initial wave energy into a few modes with small length scales, which may lead to the onset of Langmuir turbulence in laboratory as well as space plasmas.
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| 27843. |
- Banerjee, Santo, et al.
(författare)
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Spatiotemporal evolution in a (2+1)-dimensional chemotaxis model
- 2012
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Ingår i: Physica A. - Amsterdam : Elsevier. - 0378-4371 .- 1873-2119. ; 391:1-2, s. 107-112
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Tidskriftsartikel (refereegranskat)abstract
- Simulations are performed to investigate the nonlinear dynamics of a (2 + 1)-dimensional chemotaxis model of Keller-Segel (KS) type, with a logistic growth term. Because of its ability to display auto-aggregation, the KS model has been widely used to simulate self-organization in many biological systems. We show that the corresponding dynamics may lead to steady-states, to divergencies in a finite time as well as to the formation of spatiotemporal irregular patterns. The latter, in particular, appears to be chaotic in part of the range of bounded solutions, as demonstrated by the analysis of wavelet power spectra. Steady-states are achieved with sufficiently large values of the chemotactic coefficient (chi) and/or with growth rates r below a critical value r(c). For r > r(c), the solutions of the differential equations of the model diverge in a finite time. We also report on the pattern formation regime, for different values of chi, r and of the diffusion coefficient D. (C) 2011 Elsevier B.V. All rights reserved.
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| 27844. |
- Banerjee, S., et al.
(författare)
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Synchronization of spatiotemporal semiconductor lasers and its application in color image encryption
- 2011
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 284:9, s. 2278-2291
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Tidskriftsartikel (refereegranskat)abstract
- Optical chaos is a topic of current research characterized by high-dimensional nonlinearity which is attributed to the delay-induced dynamics, high bandwidth and easy modular implementation of optical feedback. In light of these facts, which add enough confusion and diffusion properties for secure communications, we explore the synchronization phenomena in spatiotemporal semiconductor laser systems. The novel system is used in a two-phase colored image encryption process. The high-dimensional chaotic attractor generated by the system produces a completely randomized chaotic time series, which is ideal in the secure encoding of messages. The scheme thus illustrated is a two-phase encryption method, which provides sufficiently high confusion and diffusion properties of chaotic cryptosystem employed with unique data sets of processed chaotic sequences. In this novel method of cryptography, the chaotic phase masks are represented as images using the chaotic sequences as the elements of the image. The scheme drastically permutes the positions of the picture elements. The next additional layer of security further alters the statistical information of the original image to a great extent along the three-color planes. The intermediate results during encryption demonstrate the infeasibility for an unauthorized user to decipher the cipher image. Exhaustive statistical tests conducted validate that the scheme is robust against noise and resistant to common attacks due to the double shield of encryption and the infinite dimensionality of the relevant system of partial differential equations.
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| 27845. |
- Banerjee, Souvik, et al.
(författare)
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The dark bubbleography
- 2024
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- We present the holographic construction of the dark bubble model of dark energy and highlight the pivotal role played by the non-normalizable modes. Following the route of holographic renormalization, we show that the non-normalizable modes are essential for having a vanishing mass for the induced graviton in any braneworld model. We then apply this idea in the computation of the propagator on the wall of the dark bubble introduced in [1].
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| 27846. |
- Banerjee, S., et al.
(författare)
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Time delay in negative ion photodetachment
- 2021
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 96:11
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Tidskriftsartikel (refereegranskat)abstract
- Time delay in photodetachment has been investigated for few negative ions, Cl-, Br-, I-, and Li-. Very few studies on photodetachment time delay for negative ions are present till date and have been reviewed briefly in the present article. Different many body formalisms, like RRPA, RRPA-R and RMCTD, have been employed to obtain new results on photodetachment time delay, accounting for important electron correlations present in the negative ions studied here. Results on time delay show significant angle dependence near the threshold region, at shape resonance and at Cooper minimum region.
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| 27847. |
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| 27848. |
- Banerji, Shantanu, et al.
(författare)
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Important differences between topoisomerase-I and -II targeting agents
- 2006
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Ingår i: Cancer Biology & Therapy. - : Landes Bioscience. - 1538-4047 .- 1555-8576. ; 5:8, s. 965-966
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Commentary to: Activation of ATM and Histone H2AX Phosphorylation Induced by Mitoxantrone But Not by Topotecan is Prevented by the Antioxidant N-acetyl-L-Cysteine Xuan Huang, Akira Kurose, Toshiki Tanaka, Frank Traganos, Wei Dai and Zbigniew Darzynkiewicz
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| 27849. |
- Banert, Sebastian, et al.
(författare)
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A general double-proximal gradient algorithm for d.c. programming
- 2019
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Ingår i: Mathematical programming. - : SPRINGER HEIDELBERG. - 0025-5610 .- 1436-4646. ; 178:1-2, s. 301-326
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities of exploiting the special structure of d.c. programs, which consist of optimising the difference of convex functions, are currently more or less limited to variants of the DCA proposed by Pham Dinh Tao and Le Thi Hoai An in 1997. These assume that either the convex or the concave part, or both, are evaluated by one of their subgradients. In this paper we propose an algorithm which allows the evaluation of both the concave and the convex part by their proximal points. Additionally, we allow a smooth part, which is evaluated via its gradient. In the spirit of primal-dual splitting algorithms, the concave part might be the composition of a concave function with a linear operator, which are, however, evaluated separately. For this algorithm we show that every cluster point is a solution of the optimisation problem. Furthermore, we show the connection to the Toland dual problem and prove a descent property for the objective function values of a primal-dual formulation of the problem. Convergence of the iterates is shown if this objective function satisfies the Kurdyka-Lojasiewicz property. In the last part, we apply the algorithm to an image processing model.
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| 27850. |
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