Mapping individual electromagnetic field components inside a photonic crystal

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing waves and a subwavelength spherical scatterer is scanned inside the resulting resonator. The resonant Bloch frequencies shift depending on the electric field at the position of the scatterer. To map the electric field component Ez we measure the frequency shift in the reflection and transmission spectrum of the slab versus the scatterer position. Very good agreement is found between measurements and calculations without any adjustable parameters.Comment: 12 pages, 7 figure

Stochastic mean-field dynamics for fermions in the weak coupling limit

Assuming that the effect of the residual interaction beyond mean-field is weak and has a short memory time, two approximate treatments of correlation in fermionic systems by means of Markovian quantum jump are presented. A simplified scenario for the introduction of fluctuations beyond mean-field is first presented. In this theory, part of the quantum correlations between the residual interaction and the one-body density matrix are neglected and jumps occur between many-body densities formed of pairs of states $D=| \Phi_a > < \Phi_b |/$ where $| \Phi_a >$ and $| \Phi_b >$ are antisymmetrized products of single-particle states. The underlying Stochastic Mean-Field (SMF) theory is discussed and applied to the monopole vibration of a spherical $^{40}$Ca nucleus under the influence of a statistical ensemble of two-body contact interaction. This framework is however too simplistic to account for both fluctuation and dissipation. In the second part of this work, an alternative quantum jump method is obtained without making the approximation on quantum correlations. Restricting to two particles-two holes residual interaction, the evolution of the one-body density matrix of a correlated system is transformed into a Lindblad equation. The associated dissipative dynamics can be simulated by quantum jumps between densities written as $D = | \Phi >$ is a normalized Slater determinant. The associated stochastic Schroedinger equation for single-particle wave-functions is given.Comment: Enlarged version, 10 pages, 2 figure

Intranuclear Cascade Models Lack Dynamic Flow

peer reviewe

Elastic precession of electronic spin states in interacting integer quantum Hall edge channels

We consider the effect of Coulomb interactions in the propagation of electrons, prepared in arbitrary spin states, on chiral edge channels in the integer quantum Hall regime. Electrons are injected and detected at the same energy at different locations of the Hall bar, which is modeled as a chiral Tomonaga-Luttinger liquid. The current is computed perturbatively in the tunneling amplitudes, within a non-crossing approximation using exact solutions of the interacting Green's functions. In the case of different channel velocities, the spin precession effect is evaluated, and the role of interaction parameters and wavevectors is discussed.Comment: 5 pages, 3 figure

Les paléoenvironnements sédimentaires au Wisconsinien moyen et supérieur, île d’Anticosti, golfe du Saint-Laurent, Québec

L'inlandsis laurentidien n'a jamais dépassé la côte sud de l'île d'Anticosti ni pénétré dans le golfe du Saint-Laurent après 36 000 ans BP. De plus, la corrélation entre les unités stratigraphiques, accompagnée de datations au 14C, permet la description des événements liés à trois avancées glaciaires du Quaternaire supérieur au centre-sud de l'île. En premier lieu, dans les vallées inondées par la transgression marine, l'avènement d'une masse de glace, au Wisconsinien moyen, met en place des dépôts glacio-marins datés de 36 000 ans BP. Par contre. Ia glace s'étend sur les interfluves élevés adjacents et abandonne un till daté de 30 000 ans BP. À la limite des secteurs côtiers, le vêlage intensif du front glaciaire provoque la mise en place, sur les côtes basses, de sédiments glacio-marins datés de 28 000 ans BP, définissant par le fait même les variations importantes de la dynamique d'écoulement glaciaire dans un milieu marin. En deuxième lieu, une récurrence au Wisconsinien supérieur s'arrête à la côte sud de l'île, comme en témoigne la présence, dans les embouchures de vallées et dans la zone côtière, de sédiments glacio-marins datés de 13 500 ans BP. La mise en place de cette deuxième unité de matériel glacio-marin confirme les perturbations importantes du front glaciaire que provoque à cette latitude une grande profondeur d'eau. En troisième lieu, lors de la phase de régression marine, une calotte résiduelle qui ne couvre que les interfluves et les vallées secondaires avance à la limite de la zone côtière et met en place un matériel glacio-marin daté de 12 000 ans BP. Cette récurrence est le résultat d'un réajustement gravitationnel relié au relèvement isostatique ainsi qu'à l'abaissement du niveau marin.Anticosti Island, Gulf of St. Lawrence, Québec. The Laurentide Ice Sheet did not extend beyond the south coast of Anticosti Island into the Gulf of St. Lawrence after 36 000 years BP. Correlation of stratigraphie units, supported by 14C dates, reveal the events associated with three glacial advances during the late Quaternary of the south-central part of the island. Firstly, during the mid-Wisconsinan the ice sheet advanced into drowned valleys and deposited glacial-marine sediments dated at 36 000 yrs BP. The ice also covered adjacent interfluves and deposited a till dated at 30 000 yrs BP. Subsequently, in the present coastal zones, intense calving at the ice front resulted in the deposition of glacial-marine sediments dated at 28 000 yrs BP. This illustrates the important variations in the flow dynamic of the ice sheet in a marine environment. Secondly, during the late-Wisconsinan the ice sheet read-vanced again to the south coast of the island but did not extend into the Gulf. This is revealed by the presence of glacial-marine sediments, dated at 13 500 yrs BP, at the mouths of river valleys and in the actual low coastal zones. Deposition of this second glacial-marine unit confirmes the influence, at this latitude, of a deep water marine environment on the extension of the glacial front. Thirdly, contemporaneously with the marine regression, a residual ice cap that covered the interfluves and certain small valleys advanced to the limit of the present coastal zone and deposited glacial-marine sediments dated at 12 000 yrs BP. This advance resulted from gravitational reajustments as a function of the crustal uplift and the lowered marine limit.Das Laurentische Inlandeis ist niemals ùber die Sùdkùste der Insel Anticosti hinausgekommen, noch ist es in den Golf des Sankt Lorenz-Stroms nach 36000 v.u.Z. eingedrungen. In den von der Meer-Transgression ùberschwemmten Tâlern hat das Vordringen einer Eismasse im mittleren Wisconsin glazial-marine Ablagerungen hinterlassen, die auf 36000 Jahre v.u.Z. datiert werden. Andererseits hat sich das Eis bis auf die erhôhten angrenzenden Interfluves ausgedehnt und Geschiebelehm abgelagert, der auf 30000 Jahre v.u.Z. datiert wird. An der Grenze der Kustengebiete hat das intensive Kalben der Eisfront die Ablagerung von glazial-marinen Sedimenten an den tiefliegenden Kùsten hervorgerufen, die auf 28 000 Jahre v.u.Z. datiert werden. Hierdurch werden die erheblichen Variationen in der Strômungs-Dynamik der Eisdecke im Meeres-Milieu illustriert. Zweitens hait ein VorstoB im spàten Wisconsin an der Sùdkùste der Insel an, wie es durch glazial-marine Sedimente bestàtigt wird, die sich in den Talmùndungen und im Kùstengebiet befinden und die auf 13 500 Jahre v.u.Z. datiert werden. Die Ablagerung dieser zweiten Einheit von glazial-marinem Material bestàtigt die erheblichen Stôrungen der Eisfront, die in dieser Zone durch eine betrachtliche Wassertiefe verursacht werden. Drittens stôBt wâhrend der Phase des Sinkens des Meeresspiegels eine Restkalotte, die nur die Interfluves und die Sekundârtâler bedeckt, bis zur Grenze des Kùstengebiets vor und lagert glazial-marines Material ab, das auf 12 000 Jahre v.u.Z. datiert wird. Dieser VorstoB ist das Ergebnis einer Schwere-Wiederanpassung, in Verbindung mit einer isostatischen Anhebung und dem Sinken des Meeresspiegels

Universal and wide shear zones in granular bulk flow

We present experiments on slow granular flows in a modified (split-bottomed) Couette geometry in which wide and tunable shear zones are created away from the sidewalls. For increasing layer heights, the zones grow wider (apparently without bound) and evolve towards the inner cylinder according to a simple, particle-independent scaling law. After rescaling, the velocity profiles across the zones fall onto a universal master curve given by an error function. We study the shear zones also inside the material as function of both their local height and the total layer height.Comment: Minor corrections, accepted for PRL (4 pages, 6 figures

Diffusive counter dispersion of mass in bubbly media

We consider a liquid bearing gas bubbles in a porous medium. When gas bubbles are immovably trapped in a porous matrix by surface-tension forces, the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. Essentially, the gas solution is in local thermodynamic equilibrium with vapor phase all over the system, i.e., the solute concentration equals the solubility. When temperature and/or pressure gradients are applied, diffusion fluxes appear and these fluxes are faithfully determined by the temperature and pressure fields, not by the local solute concentration, which is enslaved by the former. We derive the equations governing such systems, accounting for thermodiffusion and gravitational segregation effects which are shown not to be neglected for geological systems---marine sediments, terrestrial aquifers, etc. The results are applied for the treatment of non-high-pressure systems and real geological systems bearing methane or carbon dioxide, where we find a potential possibility of the formation of gaseous horizons deep below a porous medium surface. The reported effects are of particular importance for natural methane hydrate deposits and the problem of burial of industrial production of carbon dioxide in deep aquifers.Comment: 10 pages, 5 figures, 1 table, Physical Review

Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow cylinders in axial magnetic fields

We show that tubes of melt cast Bi-2212 used as current leads for LTS magnets can also act as efficient magnetic shields. The magnetic screening properties under an axial DC magnetic field are characterized at several temperatures below the liquid nitrogen temperature (77 K). Two main shielding properties are studied and compared with those of Bi-2223, a material that has been considered in the past for bulk magnetic shields. The first property is related to the maximum magnetic flux density that can be screened, Blim; it is defined as the applied magnetic flux density below which the field attenuation measured at the centre of the shield exceeds 1000. For a cylinder of Bi-2212 with a wall thickness of 5 mm and a large ratio of length over radius, Blim is evaluated to 1 T at T = 10 K. This value largely exceeds the Blim value measured at the same temperature on similar tubes of Bi-2223. The second shielding property that is characterized is the dependence of Blim with respect to variations of the sweep rate of the applied field, dBapp/dt. This dependence is interpreted in terms of the power law E = Ec(J/Jc)^n and allows us to determine the exponent n of this E(J) characteristics for Bi-2212. The characterization of the magnetic field relaxation involves very small values of the electric field. This gives us the opportunity to experimentally determine the E(J) law in an unexplored region of small electric fields. Combining these results with transport and AC shielding measurements, we construct a piecewise E(J) law that spans over 8 orders of magnitude of the electric field.Comment: 16 pages, 7 figure

Exact and approximate many-body dynamics with stochastic one-body density matrix evolution

We show that the dynamics of interacting fermions can be exactly replaced by a quantum jump theory in the many-body density matrix space. In this theory, jumps occur between densities formed of pairs of Slater determinants, $D_{ab}=| \Phi_a > < \Phi_b |$, where each state evolves according to the Stochastic Schr\"odinger Equation (SSE) given in ref. \cite{Jul02}. A stochastic Liouville-von Neumann equation is derived as well as the associated Bogolyubov-Born-Green-Kirwood-Yvon (BBGKY) hierarchy. Due to the specific form of the many-body density along the path, the presented theory is equivalent to a stochastic theory in one-body density matrix space, in which each density matrix evolves according to its own mean field augmented by a one-body noise. Guided by the exact reformulation, a stochastic mean field dynamics valid in the weak coupling approximation is proposed. This theory leads to an approximate treatment of two-body effects similar to the extended Time-Dependent Hartree-Fock (Extended TDHF) scheme. In this stochastic mean field dynamics, statistical mixing can be directly considered and jumps occur on a coarse-grained time scale. Accordingly, numerical effort is expected to be significantly reduced for applications.Comment: 12 pages, 1 figur