Full sky harmonic analysis hints at large UHECR deflections

The full-sky multipole coefficients of the ultra-high energy cosmic ray (UHECR) flux have been measured for the first time by the Pierre Auger and Telescope Array collaborations using a joint data set with E > 10 EeV. We calculate these harmonic coefficients in the model where UHECR are protons and sources trace the local matter distribution, and compare our results with observations. We find that the expected power for low multipoles (dipole and quadrupole, in particular) is sytematically higher than in the data: the observed flux is too isotropic. We then investigate to which degree our predictions are influenced by UHECR deflections in the regular Galactic magnetic field (GMF). It turns out that the UHECR power spectrum coefficients $C_\ell$ are quite insensitive to the effects of the GMF, so it is unlikely that the discordance can be reconciled by tuning the GMF model. On the contrary, a sizeable fraction of uniformly distributed flux (representing for instance an admixture of heavy nuclei with considerably larger deflections) can bring simulations and observations to an accord.Comment: 8 pages, 4 figures and one table, JETPL style -- v2 as published in JETP

Simulated testing of an adaptive multimedia information retrieval system

The Semantic Gap is considered to be a bottleneck in image and video retrieval. One way to increase the communication between user and system is to take advantage of the user's action with a system, e.g. to infer the relevance or otherwise of a video shot viewed by the user. In this paper we introduce a novel video retrieval system and propose a model of implicit information for interpreting the user's actions with the interface. The assumptions on which this model was created are then analysed in an experiment using simulated users based on relevance judgements to compare results of explicit and implicit retrieval cycles. Our model seems to enhance retrieval results. Results are presented and discussed in the final section

Nonlinear effects of phonon fluctuations on transport through nanoscale junctions

We analyze the effect of electron-phonon coupling on the full counting statistics of a molecular junction beyond the lowest order perturbation theory. Our approach allows to take into account analytically the feedback between the non-equilibrium phonon and electronic distributions in the quantum regime. We show that even for junctions with high transmission and relatively weak electron-phonon coupling this feedback gives rise to increasingly higher nonlinearities in the voltage dependence of the cumulants of the transmitted charges distribution.Comment: 4 pages, 3 figure

Local Observables in a Landscape of Infrared Gauge Modes

Cosmological local observables are at best statistically determined by the fundamental theory describing inflation. When the scalar inflaton is coupled uniformly to a collection of subdominant massless gauge vectors, rotational invariance is obeyed locally. However, the statistical isotropy of fluctuations is spontaneously broken by gauge modes whose wavelength exceed our causal horizon. This leads to a landscape picture where primordial correlators depend on the position of the observer. We compute the stochastic corrections to the curvature power spectrum, show the existence of a new local observable (the shape of the quadrupole), and constrain the theory using Planck limits.Comment: 5 pages, 3 figures, v2: minor updates, matches version published in Physics Letters

Brane Cosmology and KK Gravitinos

The cosmology of KK gravitinos in models with extra dimensions is considered. The main result is that the production of such KK modes is not compatible with an epoch of non--standard expansion after inflation. This is so because the BBN constraint on the zero mode forces the reduced five dimensional Planck mass $M_5$ down to values much smaller than the usual four dimensional one, but this in turn implies many KK states available for a given temperature. Once these states are taken into account one finds that there is no $M_5$ for which the produced KK gravitinos satisfy BBN and overclosure constraints. This conclusion holds for both flat and warped models in which only gravity propagates in the full spacetime.Comment: 19 pages, references added, IoP styl

Natural extension of the Generalised Uncertainty Principle

We discuss a gedanken experiment for the simultaneous measurement of the position and momentum of a particle in de Sitter spacetime. We propose an extension of the so-called generalized uncertainty principle (GUP) which implies the existence of a minimum observable momentum. The new GUP is directly connected to the nonzero cosmological constant, which becomes a necessary ingredient for a more complete picture of the quantum spacetime.Comment: 4 pages, 1 figure, v2 with added references, revised and extended as published in CQ

Dynamics of a trapped Fermi gas in the BCS phase

We derive semiclassical transport equations for a trapped atomic Fermi gas in the BCS phase at temperatures between zero and the superfluid transition temperature. These equations interpolate between the two well-known limiting cases of superfluid hydrodynamics at zero temperature and the Vlasov equation at the critical one. The linearized version of these equations, valid for small deviations from equilibrium, is worked out and applied to two simple examples where analytical solutions can be found: a sound wave in a uniform medium and the quadrupole excitation in a spherical harmonic trap. In spite of some simplifying approximations, the main qualitative results of quantum mechanical calculations are reproduced, which are the different frequencies of the quadrupole mode at zero and the critical temperature and strong Landau damping at intermediate temperatures. In addition we suggest a numerical method for solving the semiclassical equations without further approximations.Comment: 15 pages, 4 figures; v2: discussion and references adde

Glasgow University at TRECVID 2006

In the first part of this paper we describe our experiments in the automatic and interactive search tasks of TRECVID 2006. We submitted five fully automatic runs, including a text baseline, two runs based on visual features, and two runs that combine textual and visual features in a graph model. For the interactive search, we have implemented a new video search interface with relevance feedback facilities, based on both textual and visual features. The second part is concerned with our approach to the high-level feature extraction task, based on textual information extracted from speech recogniser and machine translation outputs. They were aligned with shots and associated with high-level feature references. A list of significant words was created for each feature, and it was in turn utilised for identification of a feature during the evaluation

Přesnost měření v senzorových systémech s optovláknovými Braggovými mřížkami

Práce se zabývá aplikací optovláknových Braggových mřížek (FBG) v senzorice a nalyzuje faktory, které ovlivňují přesnost vyhodnocování snímaných veličin. Zaměřili jsme pozornost na spektrální měření posunu maxima reflexivity snímací mřížky, které má potenciál dosažení nejvyšších přesností měření. V práci analyzujeme skenovací způsob vyhodnocení spektra a jeho změn jako nejvhodnější metodu pro průmyslové aplikace, která poskytuje širokou volbu přijatelného kompromisu mezi rychlostí vyčítání hodnot spektrálních změn a přesností měření. Veličina, která zásadně ovlivňuje přesnost měření, je šum superponovaný v přijímači na časový signál odezvy reflexivity měřící mřížky ozařované periodicky přelaďovaným úzkopásmovým optickým zdrojem. Práce analyzuje vliv tohoto šumu na měření a zkoumá parametry skenovacího optického zdroje a vlastnosti měřící mřížky z pohledu dosažitelné přesnosti měření. Pro hodnocení vhodnosti mřížky a parametrů skenování k přesnému měření zavádíme parametr šumová šířka spektra mřížky a šumová šířka skenování spektra mřížky. V práci sou naznačeny souvislosti technologických kroků výrobního procesu mřížky s odrazivostí mřížky kritickou pro minimalizaci měřících chyb. Význam šířky spektra měřící mřížky na přesnost měření vedl ke zkoumání možností apodizace mřížek, tedy vytváření mřížkových struktur s podélně proměnným profilem amplitudy změn indexu lomu.. Analýza apodizačních profilů a technické možnosti přípravy mřížek s apodizací nás přivedly k řešení čistě apodizovaných mřížkových struktur, které je realizovatelné technikou vícenásobné příčné expozice vlákna interferenčním polem fázové mřížky ozářené výkonným UV laserem. Je představen design mřížky s potenciálem významnéhu zvýšení přesnosti detekce posunu spektra