On the problem of mass-dependence of the two-point function of the real scalar free massive field on the light cone

We investigate the generally assumed inconsistency in light cone quantum field theory that the restriction of a massive, real, scalar, free field to the nullplane $\Sigma=\{x^0+x^3=0\}$ is independent of mass \cite{LKS}, but the restriction of the two-point function depends on it (see, e.g., \cite{NakYam77, Yam97}). We resolve this inconsistency by showing that the two-point function has no canonical restriction to $\Sigma$ in the sense of distribution theory. Only the so-called tame restriction of the two-point function exists which we have introduced in \cite{Ull04sub}. Furthermore, we show that this tame restriction is indeed independent of mass. Hence the inconsistency appears only by the erroneous assumption that the two-point function would have a (canonical) restriction to $\Sigma$.Comment: 10 pages, 2 figure

References

www.geosci-model-dev-discuss.net/7/5141/2014/ doi:10.5194/gmdd-7-5141-2014 © Author(s) 2014. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD if available. A global finite-element shallow-water model supporting continuous and discontinuous element

“Ciudadanos normales” versus “ desgobernados”: categorías policiales de manifestantes en Alemania

The paper investigates police perceptions of protesters. Based on group discussions with riot police and interviews with high ranking officers, six domains are analysed as dimensions of a risk constellation contributing to the emergence of an enemy image of the protester. The findings suggest that labels describing the “police counterpart” often express distance and opposition (1) and depoliticise demonstrations (2). Furthermore, formal (3) and informal (4) categorisations of protesters as well as the perception of indications of threat in policing practice (5) are examined. Bipolar patterns of classification of protesters were found to be influential. Classifications are partly based in the law and partly in particularistic and normative subcultural attributions of legitimacy which police transfer into their organisational interpretive schemata distinguishing between legality/illegality. For explanatory means the study utilises perspectives of organisational sociology as well as the cultural distance between the police and the protesters (6). This is further elaborated using the social figure of the “normal citizen”, in which specific police conceptions of normality are condensed and which serves as a threshold for the perception of deviant protesters. Besides the implications for theory of democracy of the analysed clichés and enemy images the findings conclusively suggest that the distanced to hostile relationship between the police and some protesters does not merely represent a pedagogical or “practical” problem of the police, but is the expression of a certain conflict structure. In this structure organisational and individual factors on the side of the police as well as their actual conflict experience at demonstrations converge.O jornal investiga as perceções da polícia sobre os manifestantes. Com base em discussões de grupo com a polícia de choque e entrevistas com policiais de alto escalão, seis domínios são analisados como dimensões de uma constelação de risco que contribui para o surgimento de uma imagem do manifestante como inimigo. Os resultados sugerem que os rótulos que descrevem a "contraparte policial" frequentemente expressam distância e oposição (1) e despolitizam as manifestações (2). Além disso, são examinadas as categorizações formais (3) e informais (4) de manifestantes, bem como a perceção de indícios de ameaça na prática policial (5). Verificou-se que os padrões bipolares de classificação dos manifestantes são influentes. As classificações baseiam-se parcialmente na lei e parcialmente em atribuições subculturais particularistas e normativas de legitimidade que a polícia transfere para os seus esquemas interpretativos organizacionais, distinguindo entre legalidade/ilegalidade. Enquanto meios explicativos, o estudo utiliza perspetivas da sociologia organizacional, bem como a distância cultural entre a polícia e os manifestantes (6). Uma elaboração analítica adicional utiliza a figura social do “cidadão normal”, na qual as conceções específicas de normalidade da polícia são condensadas e que serve como um limiar para a perceção de manifestantes desviantes. Para além das implicações para a teoria da democracia dos clichês e imagens de inimigo analisados, os resultados sugerem de forma conclusiva que a distância da relação hostil entre a polícia e alguns manifestantes não representa meramente um problema pedagógico ou “prático” da polícia, mas é a expressão de uma certa estrutura de conflito. Nessa estrutura, fatores organizacionais e individuais do lado da polícia, bem como a sua experiência real de conflito nas manifestações, convergem.L’article enquête sur la façon dont les manifestants sont perçus par la police. À partir de discussions de groupe avec des CRS et d’entretiens avec des hauts gradés, il analyse six domaines de risque qui concourent à faire du manifestant un ennemi. Les résultats suggèrent que les étiquettes utilisées par les policiers expriment souvent un fossé et une opposition (1) et dépolitisent les manifestations (2). Les catégorisations formelles (3) et informelles (4) des manifestants sont également analysées, ainsi que la perception d’indices de menace dans la pratique policière (5). On constate que les modèles bipolaires de classement des manifestants ont une influence. Les classements se basent en partie sur la loi et en partie sur des attributions subculturelles particularistes et normatives de légitimité que la police transfère dans ses schémas interprétatifs organisationnels en faisant une distinction entre légalité et illégalité. L’étude utilise comme moyens explicatifs les perspectives de la sociologie organisationnelle, ainsi que le fossé culturel entre la police et les manifestants (6). Une autre élaboration analytique utilise la figure sociale du “citoyen normal”, qui condense les conceptions spécifiques de normalité de la police et qui sert de seuil à la perception des manifestants déviants. En plus des implications que ces clichés et ces images d’ennemi peuvent avoir pour la théorie de la démocratie, les résultats suggèrent clairement que la relation hostile entre la police et certains manifestants ne reflète pas seulement un problème pédagogique ou “pratique” de la police, mais elle est l’expression d’une certaine structure de conflit, où convergent des facteurs organisationnels et individuels du côté de la police, ainsi que leur expérience réelle du conflit dans les manifestations.El periódico investiga las percepciones de la policía sobre los manifestantes. Con base en discusiones de grupo con la policía de choque y entrevistas con policías de alto rango, son analizados seis dominios como dimensiones de una constelación de riesgo que contribuye para el surgimiento de una imagen del manifestante como enemigo. Los resultados sugieren que las etiquetas que describen a la “contraparte policial” frecuentemente expresan distancia y oposición (1) y despolitizan las manifestaciones (2). Además, son examinadas las categorías formales (3) e informales (4) de manifestantes, así como la percepción de indicios de amenaza en la práctica policial (5). Se constató que los patrones bipolares de clasificación de los manifestantes son influyentes. Las clasificaciones se basan parcialmente en la ley y parcialmente en atribuciones subculturales particulares y normativas de legitimidad que la policía transfiere para sus esquemas interpretativos organizacionales distinguiendo entre legalidad/ilegalidad. En relación a medios explicativos, el estudio utiliza perspectivas de la sociología organizacional, así como la distancia cultural entre la policía y los manifestantes (6). Una elaboración analítica adicional utiliza la figura social del “ciudadano normal”, en la cual las concepciones específicas de normalidad de la policía son condensadas y que sirve como un umbral para la percepción de manifestantes fuera del orden. Más allá de las implicaciones para la teoría de la democracia de los clichés e imágenes del enemigo analizados, los resultados sugieren de forma conclusiva que la distancia de la relación hostil entre la policía y algunos manifestantes no representa meramente un problema pedagógico o “práctico” de la policía, más sí la expresión de una cierta estructura de conflicto. En esa estructura, convergen factores organizacionales e individuales del lado de la policía, así como su experiencia real de conflicto en las manifestaciones

Molecular effects in the ionization of N2_2, O2_2 and F2_2 by intense laser fields

In this paper we study the response in time of N$_2$, O$_2$ and F$_2$ to laser pulses having a wavelength of 390nm. We find single ionization suppression in O$_2$ and its absence in F$_2$, in accordance with experimental results at $\lambda = 800$nm. Within our framework of time-dependent density functional theory we are able to explain deviations from the predictions of Intense-Field Many-Body $S$-Matrix Theory (IMST). We confirm the connection of ionization suppression with destructive interference of outgoing electron waves from the ionized electron orbital. However, the prediction of ionization suppression, justified within the IMST approach through the symmetry of the highest occupied molecular orbital (HOMO), is not reliable since it turns out that, e.g. in the case of F$_2$, the electronic response to the laser pulse is rather complicated and does not lead to dominant depletion of the HOMO. Therefore, the symmetry of the HOMO is not sufficient to predict ionization suppression. However, at least for F$_2$, the symmetry of the dominantly ionized orbital is consistent with the non-suppression of ionization.Comment: 19 pages, 5 figure

Anisotropic splitting of intersubband spin plasmons in quantum wells with bulk and structural inversion asymmetry

In semiconductor heterostructures, bulk and structural inversion asymmetry and spin-orbit coupling induce a k-dependent spin splitting of valence and conduction subbands, which can be viewed as being caused by momentum-dependent crystal magnetic fields. This paper studies the influence of these effective magnetic fields on the intersubband spin dynamics in an asymmetric n-type GaAs/AlGaAs quantum well. We calculate the dispersions of intersubband spin plasmons using linear response theory. The so-called D'yakonov-Perel' decoherence mechanism is inactive for collective intersubband excitations, i.e., crystal magnetic fields do not lead to decoherence of spin plasmons. Instead, we predict that the main signature of bulk and structural inversion asymmetry in intersubband spin dynamics is a three-fold, anisotropic splitting of the spin plasmon dispersion. The importance of many-body effects is pointed out, and conditions for experimental observation with inelastic light scattering are discussed.Comment: 8 pages, 6 figure

Overexpression of connexin 43 using a retroviral vector improves electrical coupling of skeletal myoblasts with cardiac myocytes in vitro.

BACKGROUND: Organ transplantation is presently often the only available option to repair a damaged heart. As heart donors are scarce, engineering of cardiac grafts from autologous skeletal myoblasts is a promising novel therapeutic strategy. The functionality of skeletal muscle cells in the heart milieu is, however, limited because of their inability to integrate electrically and mechanically into the myocardium. Therefore, in pursuit of improved cardiac integration of skeletal muscle grafts we sought to modify primary skeletal myoblasts by overexpression of the main gap-junctional protein connexin 43 and to study electrical coupling of connexin 43 overexpressing myoblasts to cardiac myocytes in vitro. METHODS: To create an efficient means for overexpression of connexin 43 in skeletal myoblasts we constructed a bicistronic retroviral vector MLV-CX43-EGFP expressing the human connexin 43 cDNA and the marker EGFP gene. This vector was employed to transduce primary rat skeletal myoblasts in optimised conditions involving a concomitant use of the retrovirus immobilising protein RetroNectin and the polycation transduction enhancer Transfectam. The EGFP-positive transduced cells were then enriched by flow cytometry. RESULTS: More than four-fold overexpression of connexin 43 in the transduced skeletal myoblasts, compared with non-transduced cells, was shown by Western blotting. Functionality of the overexpressed connexin 43 was demonstrated by microinjection of a fluorescent dye showing enhanced gap-junctional intercellular transfer in connexin 43 transduced myoblasts compared with transfer in non-transduced myoblasts. Rat cardiac myocytes were cultured in multielectrode array culture dishes together with connexin 43/EGFP transduced skeletal myoblasts, control non-transduced skeletal myoblasts or alone. Extracellular field action potential activation rates in the co-cultures of connexin 43 transduced skeletal myoblasts with cardiac myocytes were significantly higher than in the co-cultures of non-transduced skeletal myoblasts with cardiac myocytes and similar to the rates in pure cultures of cardiac myocytes. CONCLUSION: The observed elevated field action potential activation rate in the co-cultures of cardiac myocytes with connexin 43 transduced skeletal myoblasts indicates enhanced cell-to-cell electrical coupling due to overexpression of connexin 43 in skeletal myoblasts. This study suggests that retroviral connexin 43 transduction can be employed to augment engineering of the electrocompetent cardiac grafts from patients own skeletal myoblasts

Momentum space tomographic imaging of photoelectrons

We apply tomography, a general method for reconstructing 3-D distributions from multiple projections, to reconstruct the momentum distribution of electrons produced via strong field photoionization. The projections are obtained by rotating the electron distribution via the polarization of the ionizing laser beam and recording a momentum spectrum at each angle with a 2-D velocity map imaging spectrometer. For linearly polarized light the tomographic reconstruction agrees with the distribution obtained using an Abel inversion. Electron tomography, which can be applied to any polarization, will simplify the technology of electron imaging. The method can be directly generalized to other charged particles.Comment: Accepted by J. Phys.

About possible contribution of intrinsic charm component to inclusive spectra of charmed mesons

We calculate differential energy spectra ($x_F$-distributions) of charmed particles produced in proton-nucleus collisions, assuming the existence of intrinsic heavy quark components in the proton wave function. For the calculation, the recently proposed factorization scheme is used, based on the Color Glass Condensate theory and specially suited for predictions of a production of particles with large rapidities. It is argued that the intrinsic charm component can, if it exists, dominate in a sum of two components, intrinsic + extrinsic, of the inclusive spectrum of charmed particles produced in proton-nucleus collisions at high energies, in the region of medium $x_F$, $0.15 < x_F < 0.7$, and can give noticeable contribution to atmospheric fluxes of prompt muons and neutrinos.Comment: 10 pages, 4 figures. Version published in J. Phys. G

Time-dependent density-functional theory for ultrafast interband excitations

We formulate a time-dependent density functional theory (TDDFT) in terms of the density matrix to study ultrafast phenomena in semiconductor structures. A system of equations for the density matrix components, which is equivalent to the time-dependent Kohn-Sham equation, is derived. From this we obtain a TDDFT version of the semiconductor Bloch equations, where the electronic many-body effects are taken into account in principle exactly. As an example, we study the optical response of a three-dimensional two-band insulator to an external short-time pulsed laser field. We show that the optical absorption spectrum acquires excitonic features when the exchange-correlation potential contains a $1/q^{2}$ Coulomb singularity. A qualitative comparison of the TDDFT optical absorption spectra with the corresponding results obtained within the Hartree-Fock approximation is made