Supercurrent survival under Rosen-Zener quench of hard core bosons

We study the survival of super-currents in a system of impenetrable bosons subject to a quantum quench from its critical superfluid phase to an insulating phase. We show that the evolution of the current when the quench follows a Rosen-Zener profile is exactly solvable. This allows us to analyze a quench of arbitrary rate, from a sudden destruction of the superfluid to a slow opening of a gap. The decay and oscillations of the current are analytically derived, and studied numerically along with the momentum distribution after the quench. In the case of small supercurrent boosts $\nu$, we find that the current surviving at long times is proportional to $\nu^3$

The Perpetuation of Graffiti Art Subculture

Graffiti art and the subculture that supports it is a form of graffiti that differs from gang graffiti, immediate graffiti, and street art. This research is a qualitative analysis using partial participant observation of a graffiti art subculture in a Midwestern city. Six themes which characterize this subculture were individual identity, communication, competition, criminality, aesthetic criteria, and changing forms of communication. The implications of the findings for labeling theory and differential association theories are discussed

Dramatikus gyakorlatok az idegennyelv-tanításban

A szerepjáték, dramatikus gyakorlat, drámajáték az idegen nyelv tanításában is jól ismert fogalmak Az alábbiakban csak a dramatikus gyakorlatot mutatjuk be

Physics of hollow Bose-Einstein condensates

Bose-Einstein condensate shells, while occurring in ultracold systems of coexisting phases and potentially within neutron stars, have yet to be realized in isolation on Earth due to the experimental challenge of overcoming gravitational sag. Motivated by the expected realization of hollow condensates by the space-based Cold Atomic Laboratory in microgravity conditions, we study a spherical condensate undergoing a topological change from a filled sphere to a hollow shell. We argue that the collective modes of the system show marked and robust signatures of this hollowing transition accompanied by the appearance of a new boundary. In particular, we demonstrate that the frequency spectrum of the breathing modes shows a pronounced depression as it evolves from the filled sphere limit to the hollowing transition. Furthermore, when the center of the system becomes hollow surface modes show a global restructuring of their spectrum due to the availability of a new, inner, surface for supporting density distortions. We pinpoint universal features of this topological transition as well as analyse the spectral evolution of collective modes in the experimentally relevant case of a bubble-trap.Comment: 8 pages, 4 figure

Inelastic neutron scattering signal from deconfined spinons in a fractionalized antiferromagnet

We calculate the contribution of deconfined spinons to inelastic neutron scattering (INS) in the fractionalized antiferromagnet (AF*), introduced elsewhere. We find that the presence of free spin-1/2 charge-less excitations leads to a continuum INS signal above the Neel gap. This signal is found above and in addition to the usual spin-1 magnon signal, which to lowest order is the same as in the more conventional confined antiferromagnet. We calculate the relative weights of these two signals and find that the spinons contribute to the longitudinal response, where the magnon signal is absent to lowest order. Possible higher-order effects of interactions between magnons and spinons in the AF* phase are also discussed.Comment: 9 page

Static and dynamic properties of shell-shaped condensates

Static, dynamic, and topological properties of hollow systems differ from those that are fully filled as a result of the presence of a boundary associated with an inner surface. Hollow Bose-Einstein condensates (BECs) naturally occur in various ultracold atomic systems and possibly within neutron stars but have hitherto not been experimentally realized in isolation on Earth because of gravitational sag. Motivated by the expected first realization of fully closed BEC shells in the microgravity conditions of the Cold Atomic Laboratory aboard the International Space Station, we present a comprehensive study of spherically symmetric hollow BECs as well as the hollowing transition from a filled sphere BEC into a thin shell through central density depletion. We employ complementary analytic and numerical techniques in order to study equilibrium density profiles and the collective mode structures of condensate shells hosted by a range of trapping potentials. We identify concrete and robust signatures of the evolution from filled to hollow structures and the effects of the emergence of an inner boundary, inclusive of a dip in breathing-mode-type collective mode frequencies and a restructuring of surface mode structure across the transition. By extending our analysis to a two-dimensional transition of a disk to a ring, we show that the collective mode signatures are an essential feature of hollowing, independent of the specific geometry. Finally, we relate our work to past and ongoing experimental efforts and consider the influence of gravity on thin condensate shells. We identify the conditions under which gravitational sag is highly destructive and study the mode-mixing effects of microgravity on the collective modes of these shells.Comment: 26 pages, 13 figure

Miért nem érti egymást szülő és pedagógus?

Tanulmányunkban a szülők és pedagógusok közötti kommunikáció gyakoriságáról és minőségéről lesz szó. Ideális esetben a két fél egymás partnere abban, hogy a gyermek minél boldogabb és sikeresebb felnőtté váljon. S bár a célban egyetértenek, az odavezető eszközökben már gyakran nincs egyetértés. A szülők és gyerekek beleszólási jogai a rendszerváltás után egy időre kiszélesedtek, jelenleg viszont a pedagógus szakma csökkenő presztízsét részben az ún. laikusok helyrerakásával igyekeznek növelni. De bárhogyan is szűkíti vagy szélesíti a szabályozás a szülők jogait, igazán eredményes oktatás csak ott zajlik, ahol a pedagógus és szülő tandemben támogatja a tanulók fejlődését. Ehhez pedig nélkülözhetetlen, hogy okos partneri viszonyt tudjanak egymással létesíteni. A tanulmány egy viszonylag friss online szülői felmérés mellett bemutatja az ezen a téren eddig született kutatási eredményeket és nemzetközi jó gyakorlatokat is

Inelastic Neutron Scattering Signal from Deconfined Spinons in a Fractionalized Antiferromagnet

We calculate the contribution of deconfined spinons to inelastic neutron scattering (INS) in the fractionalized antiferromagnet (AF*), introduced elsewhere. We find that the presence of free spin-1/2 charge-less excitations leads to a continuum INS signal above the Néel gap. This signal is found above and in addition to the usual spin-1 magnon signal, which to lowest order is the same as in the more conventional confined antiferromagnet. We calculate the relative weights of these two signals and find that the spinons contribute to the longitudinal response, where the magnon signal is absent to lowest order. Possible higher-order effects of interactions between magnons and spinons in the AF* phase are also discussed