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1.	Agarwal, Sahil, et al. (författare) Maximal stochastic transport in the Lorenz equations 2016 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 380:1-2, s. 142-146 Tidskriftsartikel (refereegranskat)abstract We calculate the stochastic upper bounds for the Lorenz equations using an extension of the background method. In analogy with Rayleigh-Benard convection the upper bounds are for heat transport versus Rayleigh number. As might be expected, the stochastic upper bounds are larger than the deterministic counterpart of Souza and Doering [1], but their variation with noise amplitude exhibits interesting behavior. Below the transition to chaotic dynamics the upper bounds increase monotonically with noise amplitude. However, in the chaotic regime this monotonicity depends on the number of realizations in the ensemble; at a particular Rayleigh number the bound may increase or decrease with noise amplitude. The origin of this behavior is the coupling between the noise and unstable periodic orbits, the degree of which depends on the degree to which the ensemble represents the ergodic set. This is confirmed by examining the close returns plots of the full solutions to the stochastic equations and the numerical convergence of the noise correlations. The numerical convergence of both the ensemble and time averages of the noise correlations is sufficiently slow that it is the limiting aspect of the realization of these bounds. Finally, we note that the full solutions of the stochastic equations demonstrate that the effect of noise is equivalent to the effect of chaos.
2.	Andersson, Patrik U, 1970, et al. (författare) Deuteron energy of 15 MK in ultra-dense deuterium without plasma formation: Temperature of the interior of the Sun 2010 Ingår i: Physics Letters A. - 0375-9601. ; 374:28, s. 2856-2860 Tidskriftsartikel (refereegranskat)abstract Deuterons are released with kinetic energy up to 630 eV from ultra-dense deuterium as shown previously, by Coulomb explosions initiated by ns laser pulses at < 1011 Wcm−2. With higher laser intensity at < 1014 Wcm−2, the initial kinetic energy now observed by TOF-MS with variable acceleration energy is up to 1100 eV per deuteron. This indicates ejection of one deuteron by Coulomb repulsion from two stationary charges in the material. It proves a full kinetic energy release of 1260 eV or a deuteron temperature of 15 MK, similar to the temperature in the interior of the Sun. Plasma processes are excluded by the sharp TOF peaks observed and by the slow signal variation with laser intensity. Deuterons with even higher energy from multiple charge repulsion are probably detected. D + D fusion processes are expected to exist in the ultra-dense phase without plasma formation.
3.	Andersson, Patrik U, 1970, et al. (författare) Superfluid ultra-dense deuterium D(-1) at room temperature 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601. ; 375, s. 1344-1347 Tidskriftsartikel (refereegranskat)abstract Ultra-dense deuterium D(−1) is expected to be both superfluid and superconductive. It is deposited on surfaces below a novel source producing a stream of D(−1) clusters. It is studied by laser probing and Coulomb explosions giving cluster fragments which are observed by time-of-flight measurements. It is observed on surfaces at a few cm height above the container below the source, and on the outside of the container. D(−1) is detected above a 1 cm long vertical capillary in vacuum (fountain effect). This suggests the existence of superfluid D(−1) which is the only material that may be superfluid at room temperature.
4.	Aydin, Alhun, et al. (författare) Discrete Density of States 2016 Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 380, s. 1236-1240 Tidskriftsartikel (refereegranskat)abstract By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they’re almost completely flattenedout after summation or integration operation. It’s seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl’s conjecture always preserve their lower error characteristic.
5.	Aydin, Alhun, et al. (författare) Discrete Nature of Thermodynamics in Confined Ideal Fermi Gases 2014 Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 378, s. 2001-2007 Tidskriftsartikel (refereegranskat)abstract Intrinsic discrete nature in thermodynamic properties of Fermi gas appears in strongly confined and degenerate conditions. For a rectangularconfinement domain, thermodynamic properties of an ideal Fermi gas are expressed in their exact summation forms. For 1D, 2D and 3D nanodomains; variations of both number of particles and internal energy per particle with chemical potential are examined. It is shown that theirrelation with chemical potential exhibits a discrete nature which allows them to take only some definite values. Furthermore, quasi-irregularoscillatory-like sharp peaks are observed in heat capacity. New nano devices can be developed based on these behaviors.
6.	aydin, Alhun, et al. (författare) Quantum oscillations in confined and degenerate Fermi gases. I. Half-vicinity model 2018 Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 382, s. 1807-1812 Tidskriftsartikel (refereegranskat)abstract We propose an analytical model for the prediction and accurate calculation of size and density dependent quantum oscillations in thermodynamic and transport properties of confined and degenerate Fermi gases. Our model considers only half-vicinity states of Fermi level. We show that the half-vicinity model quite accurately estimates quantum oscillations depending on confinement and degeneracy. Periods of quantum oscillations are even analytically expressed for one-dimensional case. Furthermore, similarities between functional behaviors of total occupancy variance and conventional density of states functions at Fermi level are discussed.
7.	Aydin, Alhun, et al. (författare) Quantum oscillations in confined and degenerate Fermi gases. II. The phase diagram and applications of half-vicinity model 2018 Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 382, s. 1813-1817 Tidskriftsartikel (refereegranskat)abstract For part I see DOI: 10 .1016 /j.physleta.2018.02.006. Size and density dependent quantum oscillations appear in Fermi gases under strong confinement and degeneracy conditions. We provide a universal recipe that explicitly separates oscillatory regime from non-oscillatory (stationary) one. A phase diagram representing stationary and oscillatory regimes on degeneracy-confinement space is proposed. Analytical expressions of phase transition interfaces are derived. The critical point, which separates entirely stationary and oscillatory regions, is determined and its dependencies on aspect ratios are examined for anisometric domains. Accuracy of the half-vicinity model and the phase diagram are verified through the quantum oscillations in electronic heat capacity and its ratio to entropy.
8.	Aydin, Alhun, et al. (författare) Quantum shape effects and novel thermodynamic behaviors at nanoscale 2019 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 383:7, s. 655-665 Tidskriftsartikel (refereegranskat)abstract Thermodynamic properties of confined systems depend on sizes of the confinement domain due to quantum nature of particles. Here we show that shape also enters as a control parameter on thermodynamic state functions. By considering specially designed confinement domains, we demonstrate how shape effects alone modify Helmholtz free energy, entropy and internal energy of a confined system. We propose an overlapped quantum boundary layer method to analytically predict quantum shape effects without even solving Schrödinger equation or invoking any other mathematical tools. Thereby we reduce a thermodynamic problem into a simple geometric one and reveal the profound link between geometry and thermodynamics. We report also a torque due to quantum shape effects. Furthermore, we introduce isoformal, shape preserving, process which opens the possibility of a new generation of thermodynamic cycles operating at nanoscale with unique features.
9.	Bengtsson, Ingemar, et al. (författare) A Kochen-Specker inequality for a SIC 2012 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 376:4, s. 374-376 Tidskriftsartikel (refereegranskat)abstract Yu and Oh (eprint) [1] have given a state-independent proof of the Kochen–Specker theorem in three dimensions using only 13 rays. The proof consists of showing that a non-contextual hidden variable theory necessarily leads to an inequality that is violated by quantum mechanics. We give a similar proof making use of 21 rays that constitute aSIC (symmetric informationally-complete positive operator-valued measure) and a complete set of MUB (mutually unbiased bases). A theory-independent inequality is also presented using the same 21 rays, as required for experimental tests of contextuality.
10.	Brodin, Gert, et al. (författare) A simple electron plasma wave 2017 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 381:11, s. 1033-1035 Tidskriftsartikel (refereegranskat)abstract Considering a class of solutions where the density perturbations are functions of time, but not of space, we derive a new exact large amplitude wave solution for a cold uniform electron plasma. This result illustrates that most simple analytical solutions can appear even if the density perturbations are large.
11.	Brodin, Gert, et al. (författare) Large amplitude electron plasma oscillations 2014 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 378:22-23, s. 1632-1635 Tidskriftsartikel (refereegranskat)abstract We consider a cold plasma in order to find new large-amplitude wave solutions in the long-wavelength limit. Accordingly we derive two generic coupled equations which describe the energy exchange between the electrostatic and electromagnetic waves. A new kind of quasi-periodic behavior is found. Our derivations may be considered as a prerequisite to extended studies of stimulated Raman scattering for cases where the wave amplitudes are so large that standard perturbation techniques are not applicable.
12.	Cabello, Adan, et al. (författare) Quantum contextuality for rational vectors 2010 Ingår i: Physics Letters A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 375:2, s. 99-99 Tidskriftsartikel (refereegranskat)abstract The Kochen-Specker theorem states that noncontextual hidden variable models are inconsistent with the quantum predictions for every yes-no question on a qutrit, corresponding to every projector in three dimensions. It has been suggested [D.A. Meyer, Phys. Rev. Lett. 83 (1999) 3751] that the inconsistency would disappear when restricting to projectors on unit vectors with rational components; that noncontextual hidden variables could reproduce the quantum predictions for rational vectors. Here we show that a qutrit state with rational components violates an inequality valid for noncontextual hidden-variable models [A.A. Klyachko et al., Phys. Rev. Lett. 101 (2008) 020403] using rational projectors. This shows that the inconsistency remains even when using only rational vectors.
13.	Chicone, C., et al. (författare) Cosmic jets 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:12, s. 1427-1430 Tidskriftsartikel (refereegranskat)abstract We discuss time-dependent gravitational fields that accelerate free test particles to the speed of light resulting in cosmic double-jet configurations. It turns out that complete gravitational collapse along a spatial axis together with corresponding expansion along the other two axes leads to the accelerated motion of free test particles up and down parallel to the collapse axis such that a double-jet pattern is asymptotically formed with respect to the collapsed configuration.
14.	Cooray, Vernon, et al. (författare) On the possibility of phosphenes being generated by the energetic radiation from lightning flashes and thunderstorms 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:42, s. 3704-3709 Tidskriftsartikel (refereegranskat)abstract After the first report of this phenomenon by Apollo 11 astronauts, experiments conducted in space and on the ground confirmed the creation of phosphenes by the interaction of energetic radiation with the human visual system. The aim of this Letter is to show that the energetic radiation generated in the form of X-rays, gamma rays, electrons and neutrons by thunderstorms and lightning is strong enough for the creation of phosphenes in humans. It is also pointed out that some of the visual observations reported during thunderstorms might be attributable to phosphenes excited by this energetic radiation.
15.	El-Awady, E. I., et al. (författare) Electron-positron-ion plasma with kappa distribution : Ion acoustic soliton propagation 2010 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:31-32, s. 3216-3219 Tidskriftsartikel (refereegranskat)abstract Progress in understanding the nonlinear ion acoustic solitary waves which accompany collisionless electron-positron-ion plasmas with high-energy electrons and positrons (represented by kappa distribution) is presented. Both small and arbitrary amplitude solitary waves are investigated by deriving Korteweg-de Vries equation and energy-integral equation (involving a Sagdeev-like pseudopotential), respectively. The existence regions of the solitary pulses are defined precisely. Furthermore, numerical calculations reveal that only supersonic pulses may exist. The dependence of the solitary excitation characteristics on the superthermal parameters, the ion temperature, and the Mach number have been investigated. The present studies might be helpful to understand the excitation of nonlinear ion acoustic. solitary pulses in interstellar medium.
16.	Ericsson, Göran, et al. (författare) Piezonuclear reactions - do they really exist? 2010 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:5, s. 750-753 Tidskriftsartikel (refereegranskat)abstract In a number of recent articles in this journal F. Cardone and collaborators have claimed the observation of several striking nuclear phenomena which they attribute to "piezonuclear reactions". One such claim [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] is that subjecting a solution of 228Th to cavitation leads to a "transformation" of thorium nuclei that is 104 times faster than the normal nuclear decay for this isotope. In a "Comment" [G. Ericsson, S. Pomp, H. Sjöstrand, E. Traneus, Phys. Lett. A 373 (2009) 3795] to the thorium work, we have criticized the evidence provided for this claim. In a "Reply" [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 3797] Cardone et al. answer only some minor points but avoid addressing the real issue. The information provided in their Reply displays a worrying lack of control of their experimental situation and the data they put forward as evidence for their claims. We point out several shortcomings and errors in the described experimental preparations, set-up and reporting, as well as in the data analysis. We conclude that the evidence presented by Cardone et al. is insufficient to justify their claims of accelerated thorium decay (by "piezonuclear reactions" or otherwise).
17.	Fang, Kun, et al. (författare) Pairing modulations and phase separation instabilities in Bi2Sr2CaCu2O8+delta 2014 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 378:3, s. 243-248 Tidskriftsartikel (refereegranskat)abstract There is growing evidence that the unconventional spatial inhomogeneities in the doped high-T-c superconductors are accompanied by the pairing of electrons, subsequent phase transitions and condensation into coherent states. We show that such pairing states can be obtained from phase separation instabilities near level crossings. Conditions for coherent pairing instabilities are examined using exact diagonalization of Hubbard-like pyramid structures under variation of coupling and interaction strengths. We also evaluate the behavior of the energy charge gap in the vicinity of level crossings using a parametrization of coupling to the apical site to represent out-of-plane effects. These results provide a simple microscopic explanation of (correlation induced) supermodulation of the coherent pairing gap observed in scanning tunneling microscopy measurements at atomic scale in Bi2Sr2CaCu2O8+delta.
18.	Fang, Kun, et al. (författare) Possible phase separation in square and honeycomb Hubbard model : A variational cluster study 2015 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 379:37, s. 2230-2238 Tidskriftsartikel (refereegranskat)abstract The VCA ground state of the 2D Hubbard model is examined for possible phase separation under hole doping manifested by spatial inhomogeneities of coexisting different electron densities at equilibrium. Phase separation is accompanied by spectral weight loss and first Brillouin zone boundary deformation. Such an instability is observed in square structures and it is absent in honeycomb lattices. To our knowledge, no previous publications have revealed relationship between a Fermi surface instability and phase separation. Our VCA calculations provide strong support for this spontaneous instability, driven by electron correlations in specific lattice geometries, proposed in our earlier publications using exact quantum cluster calculations.
19.	Fedele, Renato, et al. (författare) Mathematical and physical aspects of controlling the exact solutions of the 3D Gross-Pitaevskii equation 2010 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:5, s. 788-795 Tidskriftsartikel (refereegranskat)abstract The possibility of the decomposition of the three-dimensional (3D) Gross–Pitaevskii equation (GPE) into a pair of coupled Schrödinger-type equations, is investigated. It is shown that, under suitable mathematical conditions, it is possible to construct the exact controlled solutions of the 3D GPE from the solutions of a linear 2D Schrödinger equation coupled with a 1D nonlinear Schrödinger equation (the transverse and longitudinal components of the GPE, respectively). The coupling between these two equations is the functional of the transverse and the longitudinal profiles. The applied method of nonlinear decomposition, called the controlling potential method (CPM), yields the full 3D solution in the form of the product of the solutions of the transverse and longitudinal components of the GPE. It is shown that the CPM constitutes a variational principle and sets up a condition on the controlling potential well. Its physical interpretation is given in terms of the minimization of the (energy) effects introduced by the control. The method is applied to the case of a parabolic external potential to construct analytically an exact BEC state in the form of a bright soliton, for which the quantitative comparison between the external and controlling potentials is presented.
20.	Fiolhais, Miguel C. N., et al. (författare) A variational proof of Thomson's theorem 2016 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 380:35, s. 2703-2705 Tidskriftsartikel (refereegranskat)abstract Thomson's theorem of electrostatics, which states the electric charge on a set of conductors distributes itself on the conductor surfaces to minimize the electrostatic energy, is reviewed in this letter. The proof of Thomson's theorem, based on a variational principle, is derived for a set of normal charged conductors, with and without the presence of external electric fields produced by fixed charge distributions. In this novel approach, the variations are performed on both the charge densities and electric potentials, by means of a local Lagrange multiplier associated with Poisson's equation, constraining the two variables.
21.	Gradov, O. M., et al. (författare) Basic properties of nonlinear surface charge waves at a plasma boundary 2018 Ingår i: Physics Letters A. - : ELSEVIER SCIENCE BV. - 0375-9601 .- 1873-2429. ; 42-43, s. 3083-3085 Tidskriftsartikel (refereegranskat)abstract The nonlinear properties of surface charges are here analyzed under ideal conditions. We thus deduce a new single equation from the wellknown equations which govern the cold electron plasma motion. Simple formulas that describe the propagation of surface charge perturbations along the plasma boundary are also found. (C) 2018 Elsevier B.V. All rights reserved.
22.	Gürkan, Nilhan, et al. (författare) Realization of a holonomic quantum computer in a chain of three-level systems 2015 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 379:47-48, s. 3050-3053 Tidskriftsartikel (refereegranskat)abstract Holonomic quantum computation is the idea to use non-Abelian geometric phases to implement universal quantum gates that are robust to fluctuations in control parameters. Here, we propose a compact design for a holonomic quantum computer based on coupled three-level systems. The scheme does not require adiabatic evolution and can be implemented in arrays of atoms or ions trapped in tailored standing wave potentials.
23.	Haas, F, et al. (författare) Fluid moment hierarchy equations derived from quantum kinetic theory 2010 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:3, s. 481-484 Tidskriftsartikel (refereegranskat)abstract A set of quantum hydrodynamic equations are derived from the moments of the electrostatic mean-field Wigner kinetic equation. No assumptions are made on the particular local equilibrium or on the statistical ensemble wave functions. Quantum diffraction effects appear explicitly only in the transport equation for the heat flux triad, which is the third-order moment of the Wigner pseudo-distribution. The general linear dispersion relation is derived, from which a quantum modified Bohm–Gross relation is recovered in the long wave-length limit. Nonlinear, traveling wave solutions are numerically found in the one-dimensional case. The results shed light on the relation between quantum kinetic theory, the Bohm–de Broglie–Madelung eikonal approach, and quantum fluid transport around given equilibrium distribution functions.
24.	Hirvijoki, Eero, 1985, et al. (författare) The Gaussian Radial Basis Function Method for Plasma Kinetic Theory 2015 Ingår i: Physics Letters, Section A: General, Atomic and Solid State Physics. - : Elsevier BV. - 0375-9601. ; 379:42, s. 2735-2739 Tidskriftsartikel (refereegranskat)abstract Description of a magnetized plasma involves the Vlasov equation supplemented with the non-linear Fokker–Planck collision operator. For non-Maxwellian distributions, the collision operator, however, is difficult to compute. In this Letter, we introduce Gaussian Radial Basis Functions (RBFs) to discretize the velocity space of the entire kinetic system, and give the corresponding analytical expressions for the Vlasov and collision operator. Outlining the general theory, we also highlight the connection to plasma fluid theories, and give 2D and 3D numerical solutions of the non-linear Fokker–Planck equation. Applications are anticipated in both astrophysical and laboratory plasmas.
25.	Hussain, A., et al. (författare) On the kinetic Alfven waves in nonrelativistic spin quantum plasmas 2013 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 377:34-36, s. 2131-2135 Tidskriftsartikel (refereegranskat)abstract We have studied the effect of electron spin on the kinetic Alfven waves in the presence of uniform static magnetic field in an electron-ion plasma. We deduce that the usual kinetic Alfven waves are modified via spin quantum effects of electrons. The dimensionless parameters that determine the relative importance of the electron spin become prominent at higher densities. It is found that the kinetic Alfven wave frequency decreases due to the electron spin contribution in the kinetic limit while in the inertial limit they are almost unaffected in a hot magnetized plasma.
26.	Ibragimov, Nail H., et al. (författare) Integration by quadratures of the nonlinear Euler equations modeling atmospheric flows in a thin rotating spherical shell 2011 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 375:44, s. 3858-3865 Tidskriftsartikel (refereegranskat)abstract We study the nonlinear incompressible non-viscous fluid flows within a thin rotating atmospheric shell that serve as a simple mathematical description of an atmospheric circulation caused by the temperature difference between the equator and the poles. The model is also superimposed by a particular stationary flow which, under the assumption of no friction and a distribution of temperature dependent only upon latitude, models the zonal west-to-east flows in the upper atmosphere between the Ferrel and Polar cells. Owing to the Coriolis effects, the resulting achievable meteorological flows correspond to the asymptotical stable flows that are being translated along the equatorial plane. The exact solutions in terms of elementary functions are found by using Lie group methods.
27.	Ioannidou, Theodora, et al. (författare) Poisson hierarchy of discrete strings 2016 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 380:3, s. 333-336 Tidskriftsartikel (refereegranskat)abstract The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra.
28.	Karabetoglu, Sevan, et al. (författare) Thermosize effects in semiconductors 2017 Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 381, s. 2704-2708 Tidskriftsartikel (refereegranskat)abstract A thermosize junction consists of two different sized structures made using the same material. Classical and quantum thermosize effects (CTSEs and QTSEs), which are opposite to each other, induce a thermosize potential in a thermosize junction. A semi-analytical method is proposed to calculate thermosize potentials in wide ranges of degeneracy and confinement by considering both CTSEs and QTSEs in thermosize junctions made using semiconductors. Dependencies of thermosize potential on temperature, size, and degeneracy are examined. It is shown that a potential difference in millivolt scale can be induced as a combined effect of CTS and QTS. The highest potential is obtained in nondegenerate limit where the full analytical solution is obtained. The model can be used to design semiconductor thermosize devices for a possible experimental verification of CTSEs and QTSEs, which may lead to new nano energy conversion devices.
29.	Karimov, AR, et al. (författare) Flow oscillations in radial expansion of an inhomogeneous plasma layer 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:27, s. 2629-2636 Tidskriftsartikel (refereegranskat)abstract The cylindrically symmetric radial evolution of an inhomogeneous plasma layer expanding into vacuum is investigated nonperturbatively by first determining the spatial structure of the plasma flow structure. The evolution is then governed by a set of ordinary differential equations. The effect of the plasma inhomogeneity on the nonlinear coupling among the electron and ion flow components and oscillations is investigated
30.	Kedem, Yaron (författare) Obtaining imaginary weak values with a classical apparatus : Applications for the time and frequency domains 2014 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 378:30-31, s. 2096-2099 Tidskriftsartikel (refereegranskat)abstract Weak measurements with imaginary weak values are reexamined in light of recent experimental results. The shift of the meter, due to the imaginary part of the weak value, is derived via the probability of post-selection, which allows considering the meter as a distribution of a classical variable. The derivation results in a simple relation between the change in the distribution and its variance. By applying this relation to several experimental results, in which the meter involved the time and frequency domains, it is shown to be especially suitable for scenarios of that kind. The practical and conceptual implications of a measurement method, which is based on this relation, are discussed.
31.	Kiik, Jean-Claude, et al. (författare) On vertex conditions for elastic systems 2015 Ingår i: Physics Letters A. - Stockholm : Department of Mathematics, Stockholm University. - 0375-9601 .- 1873-2429. ; 379:34-35, s. 1871-1876 Rapport (övrigt vetenskapligt/konstnärligt)abstract In this paper vertex conditions for the fourth order differential operator on the simplest metric graph - the $ Y$-graph, -are discussed. In order to make the operator symmetric one needs to impose extra conditions on the limit values offunctions and their derivatives at the central vertex. It is shown that such conditions corresponding to the free movement of beams depend on the angles between the beams in the equilibrium position.
32.	Krawczyk, M, et al. (författare) Electronic and hole minibands in quantum wire arrays of different crystallographic structure 2010 Ingår i: PHYSICS LETTERS A. - : Elsevier BV. - 0375-9601. ; 374:4, s. 647-654 Tidskriftsartikel (refereegranskat)abstract We consider semiconductor heterostructures consisting of GaAs rods embedded in AlxGa1-xAs and disposed in sites of a Square or triangular lattice. The electronic and hole spectra around the conduction band bottom and the valence band top are examined for electrons and holes propagating in plane of periodicity, versus geometry of the lattice formed by the rods, concentration of At in the matrix material, and structural parameters including the filling fraction and the lattice constant. Our calculations use the envelope function and are based on the effective-mass approximation. We show that the electronic and hole spectra resulting from the periodicity of the heterostructure, depend on the factors considered and that the effect of lattice geometry varies substantially with lattice constant. For low lattice constant values the minigaps are significantly wider in the case of triangular lattice, while for high lattice constant values only slightly thiner minigaps Occur in the Square lattice-based arrays. We discuss the consequences of our findings for the efficiency of solar cells.
33.	Li, Jiguang, et al. (författare) MF -dependent Hyperfine Induced Transition Rates in an External Magnetic Field for Be-like 47Ti18 2011 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 375:5, s. 914-917 Tidskriftsartikel (refereegranskat)abstract Hyperfine induced 2s2pP03→2s2S01 transition rates in an external magnetic field for Be-like 47Ti were calculated based on the multiconfiguration Dirac-Fock method. It was found that the transition probability is dependent on the magnetic quantum number M of the excited state, even in the weak field. The present investigation clarifies that the difference of the hyperfine induced transition rate of Be-like Ti ions between experiment [Schippers, et al., Phys. Rev. Lett. 98 (2007) 033001(4)] and theory does not result from the influence of external magnetic field.
34.	Liberman, M. A., et al. (författare) On detonation initiation by a temperature gradient for a detailed chemical reaction models 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:17, s. 1803-1808 Tidskriftsartikel (refereegranskat)abstract The evolution from a temperature gradient to a detonation is investigated for combustion mixture whose chemistry is governed by a detailed chemical kinetics. We show that a detailed chemical reaction model has a profound effect on the spontaneous wave concept for detonation initiation by a gradient of reactivity. The evolution to detonation due to a temperature gradient is considered for hydrogen-oxygen and hydrogen-air mixtures at different initial pressures. It is shown that the minimal length of the temperature gradient for which a detonation can be ignited is much larger than that predicted from a one-step chemical model.
35.	Litvinov, Dmitry, et al. (författare) Probing the gravitational redshift with an Earth-orbiting satellite 2018 Ingår i: Physics Letters, Section A: General, Atomic and Solid State Physics. - : Elsevier BV. - 0375-9601. ; 382:33, s. 2192-2198 Tidskriftsartikel (refereegranskat)abstract We present an approach to testing the gravitational redshift effect using the RadioAstron satellite. The experiment is based on a modification of the Gravity Probe A scheme of nonrelativistic Doppler compensation and benefits from the highly eccentric orbit and ultra-stable atomic hydrogen maser frequency standard of the RadioAstron satellite. Using the presented techniques we expect to reach an accuracy of the gravitational redshift test of order 10−5, a magnitude better than that of Gravity Probe A. Data processing is ongoing, our preliminary results agree with the validity of the Einstein Equivalence Principle.
36.	Manyuhina, Oksana V., et al. (författare) Thin nematic films : Anchoring effects and stripe instability revisited 2013 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 377:13, s. 1003-1011 Tidskriftsartikel (refereegranskat)abstract We study theoretically the formation of long-wavelength instability patterns observed at spreading of nematic droplets on liquid substrates. The role of surface-like elastic terms in nematic films of submicron thickness is (re)examined by extending our previous work to hybrid aligned nematics. We identify the upper threshold for the formation of stripes and compare our results with experimental observations. We find that the wavelength and the amplitude of the in-plane director undulations can be related to the small but finite azimuthal anchoring. Within a simplified model we analyse the possibility of non-planar base state below the Barbero-Barberi critical thickness.
37.	Marklund, Mattias, et al. (författare) Gauge-free Hamiltonian structure of the spin Maxwell-Vlasov equations 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:24, s. 2362-2365 Tidskriftsartikel (refereegranskat)abstract We derive the gauge-free Hamiltonian structure of an extended kinetic theory, for which the intrinsic spin of the particles is taken into account. Such a semi-classical theory can be of interest for describing, e.g., strongly magnetized plasma systems. We find that it is possible to construct a generalized noncanonical Poisson bracket on the extended phase space, and discuss the implications of our findings, including stability of monotonic equilibria. (C) 2011 Elsevier B.V. All rights reserved.
38.	Mendonca, Jose Tito, et al. (författare) The influence of temporal coherence on the dynamical Casimir effect 2011 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 375:27, s. 2665-2669 Tidskriftsartikel (refereegranskat)abstract We study the dynamical Casimir effect in the presence of a finite coherence time, which is associated with a finite quality factor of the optical cavity. We use the time refraction model, where a fixed cavity with a modulated optical medium, replaces the empty cavity with a vibrating mirror. Temporal coherence is described with the help of cavity quasi-mode operators. Asymptotic expressions for the number of photon pairs generated from vacuum are derived.
39.	Mozafari, Elham, et al. (författare) Polaron stability in molecular crystals 2012 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 376:22, s. 1807-1811 Tidskriftsartikel (refereegranskat)abstract A semi-empirical Peierls-Holstein model is applied to studies of the stability of polarons in two-dimensional molecular crystal systems. Calculations for a broad range of intra- and inter-molecular parameters within this model were performed in order to obtain detailed knowledge concerning the stability of the polaron solution with respect to a rigid lattice band solution. For realistic values of the parameters the polaron solution is stable with a polaron energy in the range 50-100 meV. A metastable polaron solution is also identified. The polarons that result from our model are highly localized and it is questionable if adiabatic polaron transport can occur in the system.
40.	Nouri, N., et al. (författare) Topological phases in Bi/Sb planar and buckled honeycomb monolayers 2018 Ingår i: Physics Letters A. - : ELSEVIER SCIENCE BV. - 0375-9601 .- 1873-2429. ; 382:40, s. 2952-2958 Tidskriftsartikel (refereegranskat)abstract We investigate topological phases in two-dimensional Bi/Sb honeycomb crystals considering planar and buckled structures, both freestanding and deposited on a substrate. We use the multi-orbital tight-binding model and compare results with density functional theory calculations. We distinguish topological phases by calculating topological invariants, analyzing edge states properties of systems in a ribbon geometry and studying their entanglement spectra. We show that coupling to the substrate induces transition to the Z(2) topological insulator phase. It is observed that topological crystalline insulator (TCI) phase, found in planar crystals, exhibits an additional pair of edge states in both energy spectrum and entanglement spectrum. Transport calculations for TCI phase suggest robust quantized conductance even in the presence of crystal symmetry-breaking disorder. (C) 2018 Elsevier B.V. All rights reserved.
41.	Peer, J, et al. (författare) Transcranial stimulability of phosphenes by long lightning electromagnetic pulses (vol 374, pg 2932, 2010) 2010 Ingår i: PHYSICS LETTERS A. - : Elsevier BV. - 0375-9601. ; 374:47, s. 4797-4799 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
42.	Perakis, F., et al. (författare) Discrete nonlinear Schrödinger equation dynamics in complex networks 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:3, s. 676-679 Tidskriftsartikel (refereegranskat)abstract We investigate dynamical aspects of the discrete nonlinear Schrödinger equation in finite lattices. Starting from a periodic chain with nearest neighbor interactions, we insert randomly links connecting distant pairs of sites across the lattice. Using localized initial conditions we focus on the time averaged probability of occupation of the initial site as a function of the degree of complexity of the lattice and nonlinearity. We observe that selftrapping occurs at increasingly larger values of the nonlinearity parameter as the lattice connectivity increases, while close to the fully coupled network limit, localization becomes more preferred. For nonlinearity values above a certain threshold we find a reentrant localization transition, viz. localization when the number of long distant bonds is small followed by delocalization and enhanced transport at intermediate bond numbers while close to the fully connected limit localization reappears.
43.	Raischela, F., et al. (författare) Searching for optimal variables in real multivariate stochastic data 2012 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601. ; 376:30-31, s. 2081-2089 Tidskriftsartikel (refereegranskat)abstract By implementing a recent technique for the determination of stochastic eigendirections of two coupled stochastic variables, we investigate the evolution of fluctuations of NO2 concentrations at two monitoring stations in the city of Lisbon, Portugal. We analyze the stochastic part of the measurements recorded at the monitoring stations by means of a method where the two concentrations are considered as stochastic variables evolving according to a system of coupled stochastic differential equations. Analysis of their structure allows for transforming the set of measured variables to a set of derived variables, one of them with reduced stochasticity. For the specific case of NO2 concentration measures, the set of derived variables are well approximated by a global rotation of the original set of measured variables. We conclude that the stochastic sources at each station are independent from each other and typically have amplitudes of the order of the deterministic contributions. Such findings show significant limitations when predicting such quantities. Still, we briefly discuss how predictive power can be increased in general in the light of our methods. (C) 2012 Elsevier B.V. All rights reserved.
44.	Shukla, Nitin, et al. (författare) Generation of zonal magnetic fields by drift waves in a current carrying nonuniform magnetoplasma 2010 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:24, s. 2461-2463 Tidskriftsartikel (refereegranskat)abstract It is shown that zonal magnetic fields (ZMFs) can be nonlinearly excited by incoherent drift waves (DWs) in a current carrying nonuniform magnetoplasma. The dynamics of incoherent DWs in the presence of ZMFs is governed by a wave-kinetic equation. The governing equation for ZMFs in the presence of nonlinear advection force of the DWs is obtained from the parallel component of the electron momentum equation and the Faraday law. Standard techniques are used to derive a nonlinear dispersion relation, which depicts instability via which ZMFs are excited in plasmas. ZMFs may inhibit the turbulent cross-field particle and energy transport in a nonuniform magnetoplasma.
45.	Shukla, Nitin, et al. (författare) Localized excitations in a nonlinearly coupled magnetic drift wave-zonal flow system 2010 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 374:13-14, s. 1514-1516 Tidskriftsartikel (refereegranskat)abstract We consider the amplitude modulation of the magnetic drift wave (MOW) by zonal flows (ZFs) in a nonuniform magnetoplasma. For this purpose, we use the two-fluid model to derive a nonlinear Schrodinger equation for the amplitude modulated MDWs in the presence of the ZF potential, and an evolution equation for the ZF potential which is reinforced by the nonlinear Lorentz force of the MDWs. Our nonlinearly coupled MDW-ZFs system of equations admits stationary solutions in the form of a localized MDW envelope and a shock-like ZF potential profile.
46.	Shukla, Nitin, et al. (författare) Magnetization of a quantum plasma by photons 2010 Ingår i: PHYSICS LETTERS A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 374:15-16, s. 1749-1750 Tidskriftsartikel (refereegranskat)abstract It is shown that the ponderomotive force of large-amplitude electromagnetic waves (photons), which includes the electron spin current and exchange potential contributions in a quantum plasma, can generate magnetic fields. The present result can account for the magnetic fields in dense compact astrophysical objects and in the next generation laser-solid density plasma interaction experiments.
47.	Shukla, Nitin, et al. (författare) Nonlinear generation of zonal flows by ion-acoustic waves in a uniform magnetoplasma 2010 Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 374:4, s. 592-594 Tidskriftsartikel (refereegranskat)abstract It is shown that large-scale zonal flows (ZFs) can be excited by Reynolds stress of nonlinearly interacting random phase ion-acoustic waves (EIAWs) in a uniform magnetoplasma. Since ZFs are associated with poloidal sheared flows, they can tear apart short scale EIAW turbulence eddies, and hence contribute to the reduction of the cross-field turbulent transport in a magnetized plasma. (C) 2009 Elsevier B.V. All rights reserved.
48.	Shukla, Nitin, et al. (författare) The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains 2011 Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:17, s. 1809-1811 Tidskriftsartikel (refereegranskat)abstract The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains.
49.	Shukla, P.K., et al. (författare) Alfvenic shock waves in a collisional magnetoplasma 2011 Ingår i: Physics Letters A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 375:24, s. 2371-2373 Tidskriftsartikel (refereegranskat)abstract Compressional Alfvenic shock waves in a cold collisional magnetoplasma are investigated. For this purpose, we use the hydrodynamic equations and Faradays law to derive the governing nonlinear equations for the compressional Alfven waves. It is shown that the latter can appear in the form of Alfvenic shock waves.
50.	Shukla, Padma. K. (författare) Properties of electrostatic waves in ultracold neutral plasmas 2010 Ingår i: Physics Letters A. - [Shukla, P. K.] Ruhr Univ Bochum, Fak Phys & Astron, Inst Theoret Phys, D-44780 Bochum, Germany. [Shukla, P. K.] Umea Univ, Dept Phys, SE-90187 Umea, Sweden. [Shukla, P. K.] Univ Strathclyde, Dept Phys, SUPA, Glasgow G4 0NG, Lanark, Scotland. [Shukla, P. K.] Univ Tecn Lisboa, Inst Super Tecn, GoLP Inst Plasmas Fusao Nucl, P-1049001 Lisbon, Portugal. [Shukla, P. K.] Univ KwaZulu Natal, Sch Phys, ZA-4000 Durban, South Africa. [Shukla, P. K.] Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. : Elsevier BV. - 0375-9601 .- 1873-2429. ; 374:35, s. 3656-3657 Tidskriftsartikel (refereegranskat)abstract Properties of electrostatic waves in ultracold neutral plasmas (UNPs) are examined, taking accounting the polarization force arising from interactions between the thermal electrons and strongly coupled ions. It is found that the polarization force reduces the phase speed of the modified dispersive ion-acoustic (M-DIA) wave in UNPs. Possibility of the ion-lattice formation in the presence of the M-DIA wave is discussed.

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