Inner Structure of Spin^{c}(4) Gauge Potential on 4-Dimensional Manifolds

The decomposition of $Spin^{c}(4)$ gauge potential in terms of the Dirac 4% -spinor is investigated, where an important characterizing equation $\Delta A_{\mu}=-\lambda A_{\mu}$ has been discovered. Here $\lambda$ is the vacuum expectation value of the spinor field, $\lambda =\Vert \Phi \Vert ^{2}$, and $A_{\mu}$ the twisting U(1) potential. It is found that when $\lambda$ takes constant values, the characterizing equation becomes an eigenvalue problem of the Laplacian operator. It provides a revenue to determine the modulus of the spinor field by using the Laplacian spectral theory. The above study could be useful in determining the spinor field and twisting potential in the Seiberg-Witten equations. Moreover, topological characteristic numbers of instantons in the self-dual sub-space are also discussed.Comment: 11 page

Topological Vortices in Chiral Gauge Theory of Graphene

Generation mechanism of energy gaps between conductance and valence bands is at the centre of the study of graphene material. Recently Chamon, Jackiw, et al. proposed a mechanism of using a Kekul\'{e} distortion background field $\varphi$ and its induced gauge potential $A_{i}$ to generate energy gaps. In this paper various vortex structures inhering in this model are studied. Regarding $\varphi$ as a generic background field rather than a fixed Nielson-Oleson type distribution, we have found two new types of vortices on the graphene surface --- the velocity field vortices and the monopole-motion induced vortices --- from the inner structure of the potential $A_{i}$. These vortex structures naturally arise from the motion of the Dirac fermions instead of from the background distortion field.Comment: 12 page

About Zitterbewegung and electron structure

We start from the spinning electron theory by Barut and Zanghi, which has been recently translated into the Clifford algebra language. We "complete" such a translation, first of all, by expressing in the Clifford formalism a particular Barut-Zanghi (BZ) solution, which refers (at the classical limit) to an internal helical motion with a time-like speed [and is here shown to originate from the superposition of positive and negative frequency solutions of the Dirac equation]. Then, we show how to construct solutions of the Dirac equation describing helical motions with light-like speed, which meet very well the standard interpretation of the velocity operator in the Dirac equation theory (and agree with the solution proposed by Hestenes, on the basis --however-- of ad-hoc assumptions that are unnecessary in the present approach). The above results appear to support the conjecture that the Zitterbewegung motion (a helical motion, at the classical limit) is responsible for the electron spin.Comment: LaTeX; 11 pages; this is a corrected version of work appeared partly in Phys. Lett. B318 (1993) 623 and partly in "Particles, Gravity and Space-Time" (ed.by P.I.Pronin & G.A.Sardanashvily; World Scient., Singapore, 1996), p.34

Field theory of the spinning electron: Internal motions

We present here a field theory of the spinning electron, by writing down a new equation for the 4-velocity field v^mu (different from that of Dirac theory), which allows a classically intelligible description of the electron. Moreover, we make explicit the noticeable kinematical properties of such velocity field (which also result different from the ordinary ones). At last, we analyze the internal zitterbewegung (zbw) motions, for both time-like and light-like speeds. We adopt in this paper the ordinary tensorial language. Our starting point is the Barut-Zanghi classical theory for the relativistic electron, which related spin with zbw. This paper is dedicated to the memory of Asim O. Barut, who so much contributed to clarifying very many fundamental issues of physics, and whose work constitutes a starting point of these articles.Comment: standard LaTeX fil

Electron structure, Zitterbewegung, and the new non-linear Dirac-like equation

The recent literature shows a renewed interest, with various independent approaches, in the classical theories for spin. Considering the possible interest of those results, at least for the electron case, we purpose in this paper to explore their physical and mathematical meaning, by the natural and powerful language of Clifford algebras (which, incidentally, will allow us to unify those different approaches). In such theories, the ordinary electron is in general associated to the mean motion of a point-like "constituent" Q, whose trajectory is a cylindrical helix. We find, in particular, that the object Q obeys a new, non-linear Dirac-like equation, such that --when averaging over an internal cycle (which corresponds to linearization)-- it transforms into the ordinary Dirac equation (valid for the electron as a whole).Comment: LaTeX; 19 pages; this is a corrected version of work appeared partly in Hadronic J. 18 (1995) 97 and partly in Phys.Lett. B318 (1993) 48

The presentation, clinical features, complications, and treatment of congenital dacryocystocele

Purpose To determine the incidence and presenting features of congenital dacryocystocele in the United Kingdom. To report on those cases complicated by dacryocystitis, respiratory compromise, and the treatment undertaken. Methods A prospective observational study of cases of congenital dacryocystocele presenting in the United Kingdom between September 2014 and October 2015. Infants <3 months of age presenting with a cystic swelling in the medial canthal area were included. Cases were identified via the British Ophthalmology Surveillance Unit (BOSU) reporting system. Results A total of 49 cases were reported during the study period. This gives an incidence of 1 in 18 597 live births. There was a 71% response rate to the questionnaire. The average age at presentation was 16.94 days. Dacryocystoceles were unilateral in 91% of cases. Dacryocystitis was a complicating factor in 49% of patients and 17% had respiratory distress. Uncomplicated dacryocystocele responded well to conservative measures in 86%. Surgical intervention was required in 23% of patients. Those cases complicated by dacryocystitis (29%) and nasal obstruction (17%) were more likely to require surgical intervention compared to those with dacryocystocele alone (14%). Digital massage appears to reduce the likelihood of requiring surgical intervention. The mean time to resolution was 19 days. Conclusions Congenital dacryocystocele is a rare presentation in the United Kingdom. Dacryocystitis and respiratory compromise commonly complicate a dacryocystocele. The use of digital massage as an early intervention is advocated and conservative measures may be sufficient in cases of uncomplicated dacryocystocele

Hippocampal state-dependent behavioral reflex to an identical sensory input in rats.

We examined the local field potential of the hippocampus to monitor brain states during a conditional discrimination task, in order to elucidate the relationship between ongoing brain states and a conditioned motor reflex. Five 10-week-old Wistar/ST male rats underwent a serial feature positive conditional discrimination task in eyeblink conditioning using a preceding light stimulus as a conditional cue for reinforced trials. In this task, a 2-s light stimulus signaled that the following 350-ms tone (conditioned stimulus) was reinforced with a co-terminating 100-ms periorbital electrical shock. The interval between the end of conditional cue and the onset of the conditioned stimulus was 4±1 s. The conditioned stimulus was not reinforced when the light was not presented. Animals successfully utilized the light stimulus as a conditional cue to drive differential responses to the identical conditioned stimulus. We found that presentation of the conditional cue elicited hippocampal theta oscillations, which persisted during the interval of conditional cue and the conditioned stimulus. Moreover, expression of the conditioned response to the tone (conditioned stimulus) was correlated with the appearance of theta oscillations immediately before the conditioned stimulus. These data support hippocampal involvement in the network underlying a conditional discrimination task in eyeblink conditioning. They also suggest that the preceding hippocampal activity can determine information processing of the tone stimulus in the cerebellum and its associated circuits

Shear Viscosity and Oscillations of Neutron Star Crusts

We calculate the electron shear viscosity (determined by Coulomb electron collisions) for a dense matter in a wide range of parameters typical for white dwarf cores and neutron star crusts. In the density range from ~10^3 g cm^-3 to 10^7-10^10 g cm^-3 we consider the matter composed of widely abundant astrophysical elements, from H to Fe. For higher densities, 10^10-10^14 g cm^-3, we employ the ground-state nuclear composition, taking into account finite sizes of atomic nuclei and the distribution of proton charge over the nucleus. Numerical values of the viscosity are approximated by an analytic expression convenient for applications. Using the approximation of plane-parallel layer we study eigenfrequencies, eigenmodes and viscous damping times of oscillations of high multipolarity, l~500-1000, localized in the outer crust of a neutron star. For instance, at l~500 oscillations have frequencies f >= 40 kHz and are localized not deeper than ~300 m from the surface. When the crust temperature decreases from 10^9 K to 10^7 K, the dissipation time of these oscillations (with a few radial nodes) decreases from ~1 year to 10-15 days.Comment: 23 pages, 13 figure

Sur la transition entre la combustion conductive et la combustion convective dans les matériaux poreux

La transition de la déflagration à la détonation (DDT) dans les propulsifs poreux est précédée par une première transition : la transition d’une combustion conductive à une combustion convective (CCT).On a donné une condition de stabilité pour la combustion conductive pour ces propulsifs poreux dont la densité à l’état fondu est supérieure à la densité à l'état solide non brûlé