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1.
In this paper we consider a neutral spinning particle in interaction with a linear increasing rotating magnetic field and
a scalar harmonic potential using the path integral formalism. The Pauli matrices which describe the spin dynamics are replaced
by two fermionic oscillators via the Schwinger’s model. The calculations are carried out explicitly using fermionic exterior
current sources. The problem is then reduced to that of a spinning forced harmonic particle whose spin is coupled to exterior
derivative current sources. The result of the propagator is given as a series which is exactly summed up by means of the Laplace
transformation and the use of some recurrence formula of the oscillator wave functions. The energy spectrum and the corresponding
wave functions are also deduced. 相似文献
2.
S. Bellucci E. R. Bezerra de Mello A. de Padua A. A. Saharian 《The European Physical Journal C - Particles and Fields》2014,74(1):1-18
We investigate the fermionic condensate and the vacuum expectation value (VEV) of the energy-momentum tensor for a charged massive fermionic field in the geometry of a cosmic string compactified along its axis. In addition, we assume the presence of two types of magnetic fluxes: a flux running along the cosmic string and another enclosed by the compact dimension. These fluxes give rise to Aharanov–Bohm-like effects on the VEVs. The VEVs are decomposed into two parts corresponding to the geometry of a straight cosmic string without compactification plus a topological part induced by the compactification of the string axis. Both contributions are even periodic functions of the magnetic fluxes with period equal to the flux quantum. The vacuum energy density is equal to the radial stress for the parts corresponding to the straight cosmic string and the topological one. Moreover, the axial stress is equal to the energy density for the parts corresponding to the straight cosmic string; however, for massive fermionic fields this does not occur for the topological contributions. With respect to the dependence on the magnetic fluxes, both the fermionic condensate and the vacuum energy density, can be either positive or negative. Moreover, for points near the string, the main contribution to the VEVs comes from the straight cosmic string part, whereas at large distances the topological ones dominate. In addition to the local characteristics of the vacuum state, we also evaluate the part in the topological Casimir energy induced by the string. 相似文献
3.
A current algebraic approach is taken to realise the two-dimensional chiral model having anomaly analogous to that of Wess and Zumino. The conserved currents are shown to be a combination of bosonic and fermionic ones. The equations of motion of the fermions are realised through its commutation algebra with the Sugawara-like energy-momentum tensor. Quantisation of the anomaly parameter is shown to be a consequence of consistent statistics. 相似文献
4.
《Nuclear Physics B》1995,435(3):567-584
We extend the path-integral approach to bosonization to the case in which the fermionic interaction is non-local. In particular we obtain a completely bosonized version of a Thirring-like model with currents coupled by general (symmetric) bilocal potentials. The model contains the Tomonaga-Luttinger model as a special case; exploiting this fact we study the basic properties of the 1d spinless fermionic gas: fermionic correlators, the spectrum of collective modes, etc. Finally, we discuss the generalization of our procedure to the non-abelian case, thus providing a new tool to be used in the study of 1d many-body systems with spin-flipping interactions. 相似文献
5.
We consider the two-dimensional (2D) Hubbard model on the honeycomb lattice, as a model for a single layer graphene sheet
in the presence of screened Coulomb interactions. At half filling and weak enough coupling, we compute the free energy, the
ground state energy and we construct the correlation functions up to zero temperature in terms of convergent series; analyticity
is proved by making use of constructive fermionic renormalization group methods. We show that the interaction produces a modification
of the Fermi velocity and of the wave function renormalization without changing the asymptotic infrared properties of the
model with respect to the unperturbed non-interacting case; this rules out the possibility of superconducting or magnetic
instabilities in the thermal ground state. 相似文献
6.
In this Letter we construct a spinor transport theory and derive the equations of motion for the distribution functions for currents in noncollinear magnetic multilayers. We find the length scale which characterizes the transverse spin current is of the order of 3 nm for a ferromagnetic 3d transition metal such as Co; this alters one's prediction of the spin torque generated for free magnetic layers less than 3 nm. In the limit of large exchange splitting we reproduce the results previously found for spin currents across noncollinear multilayers inasmuch as there are no transverse spin currents in the layers themselves in this limit. 相似文献
7.
We consider fermionic dense matter under a magnetic field, where fermions couple minimally to gauge fields, and calculate anomalous currents at one loop. We find anomalous currents are spontaneously generated along the magnetic field but fermions only in the lowest Landau level contribute to anomalous currents. We then show that there are no more corrections to the anomalous currents from two or higher loops. 相似文献
8.
9.
We derive the N-point one-loop correlation functions for the currents of an arbitrary affine Kac-Moody algebra. The one-loop
amplitudes, which are elliptic functions defined on the torus Riemann surface, are specified by group invariant tensors and
certain constant tau-dependent functions. We compute the elliptic functions via a generating function, and explicitly construct
the invariant tensor functions recursively in terms of Young tableaux. The lowest tensors are related to the character formula
of the representation of the affine algebra. These general current algebra loop amplitudes provide a building block for open
twistor string theory, among other applications. 相似文献
10.
Introducing the fermionic R-operator and solutions of the inverse scattering problem for local fermion operators, we derive a multiple integral representation for zero-temperature correlation functions of a one-dimensional interacting spinless fermion model. Correlation functions particularly considered are the one-particle Green's function and the density–density correlation function both for any interaction strength and for arbitrary particle densities. In particular for the free fermion model, our formulae reproduce the known exact results. Form factors of local fermion operators are also calculated for a finite system. 相似文献
11.
Mihaila B Gaudio S Blagoev KB Balatsky AV Littlewood PB Smith DL 《Physical review letters》2005,95(9):090402
We propose a new method of detecting the onset of superfluidity in a two-component ultracold fermionic gas of atoms governed by an attractive short-range interaction. By studying the two-body correlation functions we find that a measurement of the momentum distribution of the density and spin-response functions allows one to access separately the normal and anomalous densities. The change in sign at low momentum transfer of the normal-ordered part of the density response function signals the transition between a BEC and a BCS regime, characterized by small and large pairs, respectively. This change in sign of the density response function represents an unambiguous signature of the BEC-to-BCS crossover. Spin rotational symmetry breaking due to the magnetic field, if observed, can be used to validate the one-channel model. 相似文献
12.
To understand the role of electron correlation and disorder on persistent currents in isolated 1D rings threaded by magnetic flux ?, we study the behavior of persistent currents in aperiodic and ordered binary alloy rings. These systems may be regarded as disordered systems with well-defined long-range order so that we do not have to perform any configuration averaging of the physical quantities. We see that in the absence of interaction, disorder suppresses persistent currents by orders of magnitude and also removes its discontinuity as a function of ?. As we introduce electron correlation, we get enhancement of the currents in certain disordered rings. Quite interestingly we observe that in some cases, electron correlation produces kink-like structures in the persistent current as a function of ?. This may be considered as anomalous Aharonov-Bohm oscillations of the persistent current and recent experimental observations support such oscillations. We find that the persistent current converges with the size of the rings. 相似文献
13.
《Physics letters. [Part B]》2001,504(3):268-274
We study the equivalence between the self-dual and the Maxwell–Chern–Simons (MCS) models coupled to dynamical, U(1) charged matter, both fermionic and bosonic. This is done through an iterative procedure of gauge embedding that produces the dual mapping of the self-dual vector field theory into a Maxwell–Chern–Simons version. In both cases, to establish this equivalence a current–current interaction term is needed to render the matter sector unchanged. Moreover, the minimal coupling of the original self-dual model is replaced by a non-minimal magnetic like coupling in the MCS side. Unlike the fermionic instance however, in the bosonic example the dual mapping proposed here leads to a Maxwell–Chern–Simons theory immersed in a field dependent medium. 相似文献
14.
S.A. Jafari 《Optics Communications》2009,282(2):317-323
When a gauge field interacts with a quantum condensed matter system, at first order of the gauge field it couples to the current operator of the electrons. Higher orders of the gauge field couple to electrons through other operators such as the stress tensor, etc. On the other hand, when one performs a measurement on a quantum system, not only the current operator, but also stress tensor operator of the electrons, etc. are hidden in the measurement, as they contribute to the gauge invariant current. We formulate a general problem of nonlinear optical response of the gauge invariant currents in presence of nonlinear couplings. We show that the new couplings along with new responses arising from field current have a very simple structure which can be formulated as time ordered multi-particle correlation functions. We also obtain their Lehman representation and thereby show that one need not use non-equilibrium formulations to deal with them. These new correlation functions suggest that in nonlinear optical response many new processes are possible. The experimental detection of the new terms in the current operator, and application corresponding multi-photon processes needs further theoretical and experimental investigations. 相似文献
15.
Akito Arima 《Hyperfine Interactions》1993,78(1-4):67-76
Studies of nuclear magnetic moments and nuclear weak interactions discussed in this Conference are reviewed. The importance of configuration mixing and meson exchange currents is examined, and it is emphasized that the second order configuration mixing (tensor correlation) is essential for the understanding of these phenomena. Recent results concerning nuclear quadrupole moments reported in this Conference are also discussed. Finally, the pairing effect in metal clusters is pointed out and the importance of measuring their spins and magnetic moments is mentioned. 相似文献
16.
Raju S 《Physical review letters》2011,106(9):091601
We show that a generalization of the Britto-Cachazo-Feng-Witten recursion relations gives a new and efficient method of computing correlation functions of the stress tensor or conserved currents in conformal field theories with an (d+1)-dimensional anti-de Sitter space dual, for d≥4, in the limit where the bulk theory is approximated by tree-level Yang-Mills theory or gravity. In supersymmetric theories, additional correlators of operators that live in the same multiplet as a conserved current or stress tensor can be computed by these means. 相似文献
17.
We bosonize the long-wavelength excitations of interacting fermions in arbitrary dimension by directly applying a suitable Hubbard-Stratonowich transformation to the Grassmannian generating functional of the fermionic correlation functions. With this technique we derive a surprisingly simple expression for the singleparticle Greens-function, which is valid for arbitrary interaction strength and can describe Fermi- as well as Luttinger liquids. Our approach sheds further light on the relation between bosonization and the random-phase approximation, and enables us to study screening in a nonperturbative way. 相似文献
18.
We study a model of strongly correlated fermions in one dimension with extended N = 2 supersymmetry. The model is related to the spin S = 1/2 XXZ Heisenberg chain at anisotropy Delta = -1/2 with a real magnetic field on the boundary. We exploit the combinatorial properties of the ground state to determine its exact wave function on finite lattices with up to 30 sites. We compute several correlation functions of the fermionic and spin fields. We discuss the continuum limit by constructing lattice observables with well defined finite-size scaling behavior. For the fermionic model with periodic boundary conditions we give the emptiness formation probability in closed form. 相似文献
19.
Oberholzer S Bieri E Schönenberger C Giovannini M Faist J 《Physical review letters》2006,96(4):046804
We investigate a beam-splitter experiment implemented in a normal-conducting fermionic electron gas in the quantum Hall regime. The cross correlations between the current fluctuations in the two exit leads of the three terminal device are found to be negative, zero, or even positive, depending on the scattering mechanism within the device. Reversal of the cross correlation sign occurs due to interaction between different edge states and does not reflect the statistics of the fermionic particles which "antibunch." 相似文献
20.
The interaction between diffuse vacuum arcs and magnetic fields applied transverse to the electrode axis has been investigated both theoretically and experimentally. For arc currents < 6 kA, Hall electric fields, generated by the interaction, bow the plasma out of contact with the anode and raise the arc voltage. In the presence of a parallel capacitor, the arc current falls to zero and the arc is extinguished. For arc currents of 6 to 15 kA, arc extinction can be achieved with an oscillatory magnetic field; during such extinctions the arc voltage remains in phase with the magnitude of the field. Arc extinction via magnetic field/vacuum arc interaction could have applications to ac-current limiters and dc breakers. The fault current limiter application is discussed in this paper. 相似文献