Current-current Coupling Research Articles

Drag-induced dynamical formation of dark solitons in Bose mixture on a ring

Andreev-Bashkin drag plays a very important role in multiple areas like superfluid mixtures, superconductors and dense nuclear matter. Here, we point out that the drag phenomenon can be also important in physics of solitons, ubiquitous objects arising in a wide array of fields ranging from tsunami waves and fiber-optic communication to biological systems. So far, fruitful studies were conducted in ultracold atomic systems where nontrivial soliton dynamics occurred due to inter-component density-density interaction. In this work we show that current-current coupling between components (Andreev-Bashkin drag) can lead to a substantially different kind of effects, unsupported by density-density interactions, such as a drag-induced dark soliton generation. This also points out that soliton dynamics can be used as a tool to experimentally study the dissipationless drag effect.

Phase transitions in a three dimensionalU(1)×U(1)lattice London superconductor: Metallic superfluid and charge-4esuperconducting states

We consider a three-dimensional lattice $U(1) \times U(1)$ superconductor in the London limit, with two individually conserved condensates. The problem, generically, has two types of intercomponent interactions of different characters. First, the condensates are interacting via a minimal coupling to the same fluctuating gauge field. A second type of coupling is the direct dissipationless drag represented by a local intercomponent current-current coupling term in the free energy functional. The interplay between these two types of interactions produces a number of physical effects not present in previously investigated $U(1)\times U(1)$ models with only one kind of intercomponent interaction. In this work, we present a study of the phase diagram of a $U(1) \times U(1)$ superconductor which includes both of these interactions. We study phase transitions and two types of competing paired phases which occur in this general model: (i) a metallic superfluid phase (where there is order only in the gauge invariant phase difference of the order parameters), (ii) a composite superconducting phase where there is order in the phase sum of the order parameters which has many properties of a single-component superconductor but with a doubled value of electric charge. We investigate the phase diagram with particular focus on what we call "preemptive phase transitions". These are phase transitions {\it unique to multicomponent condensates with competing topological objects}. A sudden proliferation of one kind of topological defects may come about due to a fluctuating background of topological defects in other sectors of the theory.

Photo-coulomb neutrino process

The photo-coulomb neutrino process (Z+γ→Z+ν+ν¯) has been considered in the electro-weak theory and the influence of this process to the evolution of stars has been outlined. The scattering cross-section of this process is calculated in both low and high energy limit. The neutrino mass has been taken into account in this calculation. In the low-energy limit the neutrino luminosity is computed in the temperature range 108–109K and is also compared to the previous result obtained according to the current-current coupling theory. The process may be significant for the evolution of stars in the later phases.

Josephson junction qubit network with current-controlled interaction

We design and evaluate a scalable charge qubit chain network with controllable current-current coupling of neighbouring qubit loops via local dc-current gates. The network allows construction of general N-qubit gates. The proposed design is in line with current main stream experiments.

Disoriented chiral condensate dynamics in the(2+1)DO(3)model

The dynamics of symmetry breaking after a quench is numerically simulated on a lattice for the (2+1)-dimensional $O(3)$ model. In addition to the standard sigma model with a temperature-dependent ${\ensuremath{\Phi}}^{4}$ potential the energy functional includes a four-derivative current-current coupling to stabilize the size of the emerging extended topological textures. The total winding number can be conserved by constraint. As a model for the chiral phase transition during the cooling phase after a hadronic collision this allows us to investigate the interference of ``baryon-antibaryon'' production with the developing disoriented aligned domains. The growth of angular correlations, condensate, and average orientation is studied in dependence of texture size, quench rate, and symmetry breaking. The classical dissipative dynamics determines the rate of energy emitted from the relaxing source for each component of the 3-vector field which provides a possible signature for the domains of disoriented chiral condensate (DCC). We find that the ``pions'' are emitted in two distinct pulses; for sufficiently small lattice size the second one carries the DCC signal, but it is strongly suppressed as compared to simultaneous ``sigma''-meson emission. We compare the resulting anomalies in the distributions of DCC pions with probabilities derived within the commonly used coherent state formalism.

The Effect of Retardation on the Spontaneous Breaking of Chiral Symmetry in GCM**The project supported in part by National Natural Scirnce Foundation of China (19875002)

An effective Hamiltonian including current-current coupling from the global color symmetry model is derived. Retardation effects are introduced by the factor , instead of in the correlation kernel, from which the retardation gap equation with coupling in the vacuum is obtained, condensations of different retardation parameters with or without the term are calculated. The results show the effects of retardation,and indicate that the typical value of is about at reasonable value of condensation. And while taking typical value of of, the condensation is about 13% larger than that with no retardation effect. With the terms, the condensation is about 17% larger than that without it for all values of the parameter . This shows that the retardation effects and the terms are important for further studying in the Iow-energy region.

The Effect of Quark Mass and α-α Term on Condensation in QCD Vacuum**The project supported in part by National Natural Science Foundation of China (19875002)

Beginning with the QCD Lagrangian in the global color symmetry model, we have derived a Hamiltonian including the lowest order current-current coupling. Taking instantaneous quadratic interaction kernel and using the Bogoliubov–Valatin transformation, we have got an effective Hamiltonian for computation. This Hamiltonian is similar to that introduced by Le Yaouanc et al., except that the α-α term has been considered here. We calculated the condensation in the BCS type of vacuum with quark mass and α-α term included. Our calculation shows that the value of condensation has increased by at least 10% with the α-α term included.

Prediction of the anomalous magnetic moment of the nucleon from the nucleon anomaly

We construct the effective anomaly lagrangian involving nucleons and photons by using the current-current coupling method. The contribution of this lagrangian to the anomalous magnetic moment of nucleon is purely isovector. The anomalous magnetic moment of the proton, κ P , can be calculated from this lagrangian and it is found to be κ P Theor. = 1.77, which is in excellent agreement with the experimental value κ P Exp. = 1.79. While for the neutron, κ N Theor. = −2.58 as compared to κ N Exp. = −1.91, is less satisfactory, but the sign is correct.

Absence of spontaneous persistent current for interacting fermions in a one-dimensional mesoscopic ring.

We address the issue of whether a system of interacting electrons confined to a one-dimensional ring can sustain a spontaneous persistent current in the absence of an externally applied flux. The current-current coupling between electrons, describing radiative back-action effects, is exactly treated in the formalism of quantum electrodynamics, where the electrons interact via the exchange of virtual photons. In addition, the instantaneous screened Coulomb potential is taken into account using the Luttinger liquid model including finite-size parity effects. The partition function is calculated exactly, with the result that the system does not possess a spontaneous persistent current. We show that, in the presence of an external flux, the amplitude of the (conventional) persistent current is reduced by quantum fluctuations of the internal transverse electromagnetic field. These corrections can be expressed in terms of the self-induction of the ring and are shown to be of first and higher order in the small dimensionless parameter \ensuremath{\alpha}${\mathit{v}}_{\mathit{F}}^{\mathrm{*}}$/c, where \ensuremath{\alpha} is the fine-structure constant and ${\mathit{v}}_{\mathit{F}}^{\mathrm{*}}$ the Fermi velocity renormalized through Coulomb interactions.

Viscous phenomena in cosmology: I. Lepton era

Shear and volume viscosity of the cosmic fluid in the lepton era are calculated with the help of relativistic kinetic theory. The cosmic fluid is taken to be a mixture of neutrinos (ν e, ν μ, ν τ), electrons (e -) and their antiparticles. The differential cross-sections are determined on the basis of the Weinberg-Salam model in the current-current coupling approximation.

Supersymmetric kaluza-klein theory

We consider a generalization of the non-Abelian gauge theories, obtained by replacing the Minkowskian space-time by the superspace, and the gauge group by itsZ2-graded extension. It seems to us that such a theory will contain all the essential features displayed by theN=1,D=10 theories after their dimensional reduction, while being much simpler to formulate. The Grassmann parity of supergauge fields introduced over the generalized graded fibre bundle is supposed to obey some strict rules, namely we propose to add up together the superspace parity and the graded-group parity of the corresponding gauge field components. This amounts to a particular choice of the supergauge, which breaks the conformal symmetry of the theory and generates masses of the Higgs scalar multiplet and of the spinor multiplet. The invariant Lagrangian is computed, which contains the Yukawa coupling, the current-current coupling and the Fermi four-point interaction. The mean mass ratio of Higgs scalarsvs. fermions is obtained. The group representation content of the theory is briefly discussed; it is shown that in this theory there is no place for quark representations if the gauge group isSU3 orSU3×U1; quarks begin to appear only with groups containingSU4 or bigger.

Theory of pure leptonic weak interaction with induced shadow states

By making use of the ε-splitting mechanism to define weak currents we construct a renormalizable theory in terms of the current-current interaction for pure leptonic weak interaction. The presence of the shadow states induced by the current-current interaction due to the ε-splitting mechanism makes, after a primary mass and wave function renormalization, the theory finite in perturbative calculations. The theory involves, in addition to the physical lepton masses, the charged current-current interaction coupling constantG c and the neutral current-current coupling constantG N. The computations for muon decay and neutrino-electron scattering processes in chain approximation show that our formalism is not ruled out in comparison with the experimental data available at the present time.

Muon-neutrino electron scattering in the theory of pure leptonic weak interaction with induced shadow states

With in the framework of the theory of shadow states (x), a finite theory for pure leptonic weak interact ion (2) was proposed before by WANG and by one of the present authors (CHIA~G). However, the theory is not sat isfactory mainly for two reasons: 1) neutral currents are not included, 2) since the shadow masses are free parameters in the theory, i t is aesthetical ly not appealing. Recently (s) i t has been observed tha t for the 4-fermion self-interaction, the current with point spl i t t ing would induce indefinite-metric states which are effectively equivalent to the shadow states in the finite quantum electrodyuamics proposed by AReas, HAN and SUD~SHAN (4), and by CHIA.~G and GL~.SO.~ (5) and also to the shadow states in the finite theory for the pure leptonic weak interact ion above-mentioned. The shadow masses are uniquely re la ted to the current-current coupling constant . By making use of the point-spl i t t ing mechanism, we have proposed (s) a finite theory for pure leptonic weak interact ion including neutral currents. In this approach the neutral currents play a crucial role in connection with the finiteness of the theory. The shadow states are induced by the neutral current self-interaction, and the theory involves only two parameters , the charged current coupling constant and the neutralcurrent coupling constant. In this note we present our computa t ion for the elast ic-scattering processes e -~a(~a) -~e-+-~(+~) . The result of our computat ion shows tha t our theory is compatible with the exper imenta l da ta available at present. To s tar t with, let us recall the in teract ion Lagrangian in ref. (6).

Electroproduction of higher spin resonances within a generalized Joss-Weinberg formalism

Electromagnetic currents for transitions from spin s to another spin s' (s' is an arbitrary irteger for s = 0 and an arbitrary halfinteger for s = 1/2) are presented in terms of spinors satisfying Weinbergs equation and generalized 2(2s + 1) x 2(2s' + 1) JoosWeinberg matrices. When the currents are transformed to the Breit frame, they involve terms which are interpreted as form factors for different electromagnetic multipole transitions. Assuming current-current coupling with one -photon exchange, the unpolarized cross section for high energy electron scattering by spin-s target (s = 0, 1/2) at electroproduction of a spin- s' resonance is obtained. (LBS)

Elastic scattering of electrons by solar neutrinos and weak interaction theories

The counting rate of recoil electrons for the elastic scattering of electrons by solar neutrinos, considering that the CNO cycle is responsible for nuclear energy generation in the sun, is calculated according to the photon-neutrino weak coupling theory as well as the current-current coupling theory. It is suggested that this result can be used to decide which type of weak interaction exists in nature.

Neutrino bremsstrahlung from a degenerate electron gas

The neutrino bremsstrahlung process is studied here according to the photon-neutrino weak coupling theory by considering the electrons as relativistic and degenerate and by adding some lattice effects at high density. The neutrino energy loss rate due to the process is then compared with that obtained according to the current-current coupling theory. It is concluded that the process is important only in cases of high dense stars when the temperature is below 107K.

Effect of neutrino emission in the sun and other main sequence stars

Pontecorvo (1959) suggested that, because of the negligible absorption of neutrino upon interaction with matter, the neutrino emission can play a significant role in stellar evolution. The profound implication of neutrino emission in the case of stellar evolution has been studied by many authors according to the current-current coupling theory which was suggested by Feynman and Gell-Mann (1958) and also by Sudarshan and Marshak (1958). According to the current-current coupling theory neutrino emission processes are only important when the temperature exceeds 4 x 108 K. Recently Bandyopadhyay (1968) has proposed that photons can interact weakly only with neutrinos. Considering this photon-neutrino coupling theory, Ray Chaudhuri (1970) has suggested that plasma neutrino emission process may prevent the helium flash in certain red giant stars. Also from an analysis of plasma neutrino emission (Ray Chaudhuri, 1970b) and neutrino synchrotron radiation (Ray Chaudhuri, 1970c) process Ray Chaudhuri has shown that the observed deficiency of white dwarf mass above 0.9M e can be explained according to the photon neutrino coupling theory. Therefore, from the observational evidence we cannot exclude the photonneutrino coupling theory; though no categorical answer from the terrestrial experiment can be given at present. The direct determination of the existence of the photonneutrino coupling theory using the elastic scattering of electrons by fission antineutrinos as attempted by Reines and Gurr (1970) (Bandyopadhyay and Ray Cbaudhurl, 1970) as well as by detection of solar neutrinos using knock on electrons produced in the neutrino electron scattering has been discussed by Ray Chaudhuri and Bandyopadhyay (1969). Again Bandyopadhyay et al. (1969) have considered the photon-neutrino elastic scattering on the basis of this photon-neutrino coupling theory and have shown that the cross section for the process v +p ~ v +p is at least an order smaller than that of the process f +p ~ n+ e + which is well within the experimental upper limit. Assuming that this type of neutrino emission processes do occur in reality, we wish to point out that the neutrino emission can also play a significant role in the Main Sequence stage (i.e. hydrogen burning); and from the balance of energy generation we point out the possible nuclear process which may be active in that stage.

Theories of weak interactions and astrophysical evidence

It has been proposed in an earlier paper that photons can interact weakly with neutrinos. Assuming this photon-neutrino coupling, the effect of energy loss due to the pair-annihilation process and the photoneutrino process on the evolutionary time scales of a 15.6M⊙ star has been discussed. In the typical model of Hayashi, Hoshi and Sugimoto (HHS), the lifetimes for carbon burning and later phases have been calculated assuming the photon-neutrino coupling, and is compared with the results obtained by HHS according to the (eν)(eν) coupling. In case of the\(\gamma \nu \bar \nu \) coupling, the ratio of the number of blue supergiants (He-burning stars) to red supergiants (stars in C-burning and later stages) is found to be ≲ 10 with the initial concentration of carbonXc=0.5, whereas according to the (eν)(eν) coupling, the corresponding ratio is found to be nearly 33. According to astrophysical observations, this ratio is found to be nearly unity within a factor 1.5. It is noted that the result according to the\(\gamma \nu \bar \nu \) coupling becomes significantly better in comparison with the (eν)(eν) coupling. Also, in view of the uncertatinties regarding the total luminosity in the red-supergiant phase as well as the rate of C+C relation, we can consider the result obtained according to the\(\gamma \nu \bar \nu \) coupling to be in reasonable proximity to the «observed» value. From this, we argue that stars seem to «favour» the photon-neutrino coupling theory rather than the current-current coupling theory of weak interactions.

Weak interaction of photons and the photoneutrino process

Assuming that photons can interact weakly with neutrinos, the cross-section for the photoneutrino process e−+γ→e−+ν+ν- has been calculated. From this, the rate of stellar energy loss has been derived and is compared with the result obtained on the basis of the current-current coupling theory.

Highly Inelastic Neutrino-Nucleon Scattering

Lower bounds for cross sections for neutrino-nucleon scattering summed over final hadron states at large energy and momentum transfer are estimated assuming the usual current-current coupling, Regge behavior, and current-algebra sum rules. The cross sections are estimated using an added assumption of pointlike baryon constituents in nucleons. The cross sections compare well with CERN bubble-chamber data.