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The classical Toda lattice with long range interaction
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 307, Issue 1 , 2003 , Pages 36-40 ; 03759601 (ISSN) ; Sharif University of Technology
Elsevier
2003
Abstract
In this Letter, I introduce a generalization of Toda lattice model, in which each site can interact with all other sites with different coupling constants. To show solvability of this model, by introducing new type of quantities (which are referred to as anti-Grassmanian numbers), the equations of motion are transformed to a Lax equation and constants of motion are derived. At last, by finding a proper r matrix involutivity of these constants are shown. © 2002 Elsevier Science B.V. All rights reserved
Transverse localization in nonlinear photonic lattices with second-order coupling
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 87, Issue 3 , March , 2013 ; 10502947 (ISSN) ; Bahrampour, A. R ; Langari, A ; Szameit, A ; Sharif University of Technology
2013
Abstract
We investigate numerically the effect of long-range interaction on the transverse localization of light. To this end, nonlinear zigzag optical waveguide lattices are applied, which allows precise tuning of the second-order coupling. We find that localization is hindered by coupling between next-nearest lattice sites. Additionally, (focusing) nonlinearity facilitates localization with increasing disorder, as long as the nonlinearity is sufficiently weak. However, for strong nonlinearities, increasing disorder results in weaker localization. The threshold nonlinearity, above which this anomalous result is observed, grows with increasing second-order coupling
Transverse Localization in Optical Waveguide Arrays
, Ph.D. Dissertation Sharif University of Technology ; Langari, Abdollah (Supervisor) ; Bahrampour, Alireza (Co-Advisor) ; Mahdavi, Mohammad (Co-Advisor)
Abstract
In recent years, a strong interplay between quantum mechanics and the physics of waveguide arrays was established based on a formal analogy between atomic and photonic lattices. The study of light evolution in photonic lattices has provided deep insights into the physics of wave function dynamics and, hence, peculiar quantum mechanical features. Arrays of evanescently coupled waveguides is a very versatile model system for discrete physics. Anderson localization and Bloch oscillations are two examples of coherent quantum transport phenomena, which have been investigated in this thesis. In the first part of this thesis, we investigate numerically the effect of long-range interaction on the...
Rydberg noisy dressing and applications in making soliton molecules and droplet quasicrystals
, Article Physical Review Research ; Volume 3, Issue 3 , 2021 ; 26431564 (ISSN) ; Sharif University of Technology
American Physical Society
2021
Abstract
The current advances in the field of ultracold atoms and atomic traps recall new controllable long-range interactions. These interactions are expected to extend the range of realizable quantum algorithms as well as provide new control mechanisms for the new types of quantum matters. This Letter presents special interatomic interactions between Rydberg-dressed atoms by manipulating the lasers' linewidth. The proposed interaction features a hybrid spatial profile containing plateaus and Gaussian peaks. Combined with dynamic control over the sign and strength of individual interaction elements, the Rydberg noisy-dressing (RnD) scheme provides a valuable interaction toolbox for quantum...
One Dimensional Extended Hubbard Model with Long Range Interactions
, M.Sc. Thesis Sharif University of Technology ; Davoudi, Bahman (Supervisor) ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis, we have studied the ground state properties of one-dimensional many body electron systems using the extended Hubbard model. Following the important work of Tremblay and Davoudi, we have used the TPSC approach to derive explicit expressions for spin and charge response functions. The response functions are expressed in terms of the free response function χ_0 and local field factors U_cc and U_ss. The local field factors can be written in terms of the pair correlation functions. Also fluctuation-dissipation theorem allows us to write pair correlation functions in terms of the structure factors. In the first part of thesis, we study the ground state properties of the system by...
Investigation on the Formation of Complex Waves by Guided Modes in Periodic 1D Structures
, M.Sc. Thesis Sharif University of Technology ; Rejaei Salmasi, Behzad (Supervisor) ; Memarian, Mohammad (Supervisor)
Abstract
Complex waves possess complex propagation constants even in the absence of losses. Such waves may be excited in open- or closed-guided wave structures such as inhomogeneously or anisotropically filled waveguides, coupled right-handed/left-handed transmission lines, and periodic structures. In the absence of losses, complex modes appear in pairs with complex conjugate propagation constants. In open-guided wave configurations, complex modes will be of either the proper or improper (leaky wave) type. Proper complex modes are accompanied by an electromagnetic field that decays exponentially in the transverse direction, away from the waveguide. By contrast, electromagnetic fields associated with...
Calculation of effective pair potential via the volumetric data
, Article Phase Transitions ; Vol. 87, issue. 1 , 2014 , pp. 38-58 ; ISSN: 01411594 ; Parsafar, G ; Sharif University of Technology
Abstract
The concept of effective pair potential (EPP), in which medium effects and contribution of long-range interactions are added to near-neighbor pair interactions, is a useful tool to derive and calculate the thermodynamic quantities. It has been shown that the extended Lennard-Jones (12, 6, 3) potential is an accurate EPP for many systems. However, the parameters of this EPP are not known for any systems. We introduce a new approach to use experimental pvT data of a fluid to calculate its EPP parameters. Such calculation has been carried out for some fluids at some temperatures. Unlike the isolated pair potential, it has been shown that the parameters significantly vary with temperature. We...
Nonlocal interactions in DNA molecules at nano-scale
, Article Scientia Iranica ; Volume 17, Issue 1 F , 2010 , Pages 23-26 ; 10263098 (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
Abstract
In this paper, we try to explain the origin of the anomalous elastic behavior of nanometersized DNA molecules, which has been observed in all-atom molecular dynamic simulations [A.K. Mazur, Biophys. J. 2006]. It is shown that this anomalous behavior is a consequence of nonlocal interactions between DNA base pairs and the intrinsic curvature of DNA. A nonlocal harmonic elastic rod model is proposed, which can successfully describe the elastic behavior of short DNA molecules
Bridged single-walled carbon nanotube-based atomic-scale mass sensors
, Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 8 , Volume 122, Issue 8 , 2016 ; 09478396 (ISSN) ; Shaat, M ; Abdelkefi, A ; Sharif University of Technology
Springer Verlag
Abstract
The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler–Bernoulli beam with von Kármán type geometric nonlinearity. Eringen’s nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue...
Spin and charge fluctuations in a one-dimensional lattice with long-range interactions
, Article Physica B: Condensed Matter ; Volume 571 , 2019 , Pages 204-209 ; 09214526 (ISSN) ; Davoudi, B ; Sharif University of Technology
Elsevier B.V
2019
Abstract
We study the competition between spin and charge fluctuations of the extended Hubbard model with on-site and dipole-dipole interactions in a one-dimensional lattice. Using the extended two-particle self consistent (ETPSC) method, we find the corresponding expressions for spin and charge response functions. In this approach, the irreducible spin and charge vertices are a function of inter-particle distance (r) and wave-number (q). This theory allows us to determine the crossover temperatures and the dominant instability as a function of U and V. The phase diagrams are obtained for several effective particle densities: n = 0.5, n = 1 and n = 4/3. Each phase diagram (U − V − T space)...
Experimental study and modelling of saturation molality of NaCl in quaternary aqueous electrolyte solutions at various temperatures
, Article Desalination ; Volume 267, Issue 2-3 , February , 2011 , Pages 228-232 ; 00119164 (ISSN) ; Roayaei, E ; Taghikhani, V ; Safekordi, A ; Zahedzadeh, M ; Sharif University of Technology
2011
Abstract
Saturation molality of sodium chloride in mixed aqueous electrolyte solutions containing NaCl, CaSO4 and Na2SO4 was measured at atmospheric pressure over the wide range of temperatures using an equilibrium cell equipped with an accurate temperature control system. The measurements were carried out at different CaSO4 and Na2SO4 concentrations. In order to check the repeatability of the experimental data for the saturation molality of NaCl, the experiments were replicated three times and the values reported were the average of the replicas. To model the data generated in this work, the PDH+UNIFAC-Dortmund activity coefficient model was used. The model used to predict the mean ionic activity...
Piezoelectric composites with periodic multi-coated inhomogeneities
, Article International Journal of Solids and Structures ; Volume 47, Issue 21 , October , 2010 , Pages 2893-2904 ; 00207683 (ISSN) ; Weng, G. J ; Kargarnovin, M. H ; Shodja, H. M ; Sharif University of Technology
Abstract
A new, robust homogenization scheme for determination of the effective properties of a periodic piezoelectric composite with general multi-coated inhomogeneities is developed. In this scheme the coating does not have to be thin, the shape and orientation of the inclusion and coatings do not have to be identical, their centers do not have to coincide, their properties do not have to remain uniform, and the microstructure can be with the 2D elliptic or the 3D ellipsoidal inclusions. The development starts from the local electromechanical equivalent inclusion principle through the introduction of the position-dependent equivalent eigenstrain and electric field. Then with a Fourier series...