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Sep 23, 2013
09/13

by
Dragomir Z. Djokovic; Simone Severini; Ferenc Szollosi

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The main question we raise here is the following one: given a real orthogonal n by n matrix X, is it true that there exists a rational orthogonal matrix Y having the same zero-pattern? We conjecture that this is the case and prove it for n

Source: http://arxiv.org/abs/0903.2853v1

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Sep 23, 2013
09/13

by
Jose M. Fernandez; Matthew J. Holman; Joshua N. Winn; Guillermo Torres; Avi Shporer; Tsevi Mazeh; Gilbert A. Esquerdo; Mark E. Everett

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We present photometry of six transits of the exoplanet XO-2b. By combining the light-curve analysis with theoretical isochrones to determine the stellar properties, we find the planetary radius to be 0.996 +0.031/-0.018 rjup and the planetary mass to be 0.565 +/- 0.054 mjup. These results are consistent with those reported previously, and are also consistent with theoretical models for gas giant planets. The mid-transit times are accurate to within 1 min and are consistent with a constant...

Source: http://arxiv.org/abs/0903.2687v1

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Sep 23, 2013
09/13

by
Satchidananda Naik

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A Closed string field theory action is formulated for $\mathcal N$ =8 self-dual supergravity which is off-shell and Lorentz covariant. The bosonic truncation in the quantum field theory limit gives the Plebanski type of action in the super space.

Source: http://arxiv.org/abs/0903.2872v1

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Sep 23, 2013
09/13

by
M. Y. Anand; B. A. I Kagali; Jayant Murthy

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In this paper we have analyzed IUE high resolution spectra of the central star (BD+602522) of the Bubble nebula. We discuss velocities of the different regions along the line of sight to the bubble. We find that the Bubble Nebula is younger (by a factor of 100) than the exciting star suggesting that either the bubble is expanding into an inhomogenuous interstellar medium or that the mechanics of the stellar wind are not fully understood.

Source: http://arxiv.org/abs/0903.2828v1

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Sep 23, 2013
09/13

by
Koichiro Sadakane; Akira Onuki; Koji Nishida; Satoshi Koizumi; Hideki Seto

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Phase transition is observed between one-phase disordered phase and an ordered phase with multi-lamellar (onion) structures in an off-critical mixture of D$_2$O and 3-methylpyridine (3MP) containing a salt at 85mM. The salt consists of hydrophilic cations and hydrophobic anions, which interact asymmetrically with the solvent composition fluctuations inducing mesophases. The structure factor of the composition distribution obtained from small-angle neutron scattering has a peak at an...

Source: http://arxiv.org/abs/0903.2303v2

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Sep 23, 2013
09/13

by
Nima Arkani-Hamed; Freddy Cachazo; Clifford Cheung; Jared Kaplan

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The simplicity and hidden symmetries of (Super) Yang-Mills and (Super)Gravity scattering amplitudes suggest the existence of a "weak-weak" dual formulation in which these structures are made manifest at the expense of manifest locality. We suggest that this dual description lives in (2,2) signature and is naturally formulated in twistor space. We recast the BCFW recursion relations in an on-shell form that begs to be transformed into twistor space. Our twistor transformation is...

Source: http://arxiv.org/abs/0903.2110v2

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Sep 23, 2013
09/13

by
F. Feroz; M. P. Hobson; L. Roszkowski; R. Ruiz de Austri; R. Trotta

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We employ two different statistical tests to examine whether, in the framework of the Constrained MSSM, the experimentally determined values of BR(b->s gamma) and the anomalous magnetic moment of the muon, (g-2), are consistent with each other. Our tests are designed to compare the theoretical predictions of the CMSSM in data space with the actual measurements, once all of the CMSSM free parameters have been integrated out and constrained using all other available data. We investigate the...

Source: http://arxiv.org/abs/0903.2487v1

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Jul 22, 2013
07/13

by
Jorge Noronha; Miklos Gyulassy; Giorgio Torrieri

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We show that far zone Mach and diffusion wake ``holograms'' produced by supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict $N_c\to\infty$ supergravity limit if Cooper-Frye hadronization is assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's...

Source: http://arxiv.org/abs/0807.1038v2

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Sep 23, 2013
09/13

by
Mark Wildon

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This paper presents a solution to the Knights and Spies Problem: In a room there are n people, each labelled with a unique number between 1 and n. A person may either be a knight or a spy. Knights always tell the truth, while spies may either lie or tell the truth, as they see fit. Each person in the room knows the identity of everyone else. Apart from this, all that is known is that strictly more knights than spies are present. Asking only questions of the form: `Person i, what is the identity...

Source: http://arxiv.org/abs/0903.2869v1

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Sep 23, 2013
09/13

by
Arie Leizarowitz

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The paper is concerned with estimating the number of integers smaller than $x$ whose largest prime divisor is smaller than $y$, denoted $\psi (x,y)$. Much of the related literature is concerned with approximating $\psi (x,y)$ by Dickman's function $\rho (u)$, where $u=\ln x/\ln y$. A typical such result is that $$ \psi (x,y)=x\rho (u)(1+o(1)) \eqno (1) $$ in a certain domain of the parameters $x$ and $y$. In this paper a different type of approximation of $\psi (x,y)$, using iterated logarithms...

Source: http://arxiv.org/abs/0903.2712v1

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Sep 23, 2013
09/13

by
Hans-Joachim Baues

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We describe a conjecture on the algebra of higher cohomology operations which leads to the computations of the differentials in the Adams spectral sequence. For this we introduce the notion of an n-th order track category which is suitable to study higher order Toda brackets and the differentials in spectral sequences. We describe various examples of higher order track categories which are topological, in particular the track category of higher cohomology operations. Also differential algebras...

Source: http://arxiv.org/abs/0903.2876v1

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Sep 23, 2013
09/13

by
K. Sakkos; J. Casulleras; J. Boronat

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High order actions proposed by Chin have been used for the first time in path integral Monte Carlo simulations. Contrarily to the Takahashi-Imada action, which is accurate to fourth order only for the trace, the Chin action is fully fourth order, with the additional advantage that the leading fourth and sixth order error coefficients are finely tunable. By optimizing two free parameters entering in the new action we show that the time step error dependence achieved is best fitted with a sixth...

Source: http://arxiv.org/abs/0903.2763v1

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Sep 21, 2013
09/13

by
L. Dunne; R. J. Ivison; S. Maddox; M. Cirasuolo; A. M. Mortier; S. Foucaud; E. Ibar; O. Almaini; C. Simpson; R. McLure

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We have studied the uJy radio properties of K-selected galaxies detected in the Ultra-Deep Survey portion of UKIDSS using 610- and 1,400-MHz images from the VLA and GMRT. These deep radio mosaics, combined with the largest and deepest K image currently available, allow high-S/N detections of many K-selected sub-populations, including sBzK and pBzK star-forming and passive galaxies. We find a strong correlation between the radio and K fluxes and a linear relationship between SFR and K...

Source: http://arxiv.org/abs/0808.3139v2

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Sep 23, 2013
09/13

by
Daniel A Spielman; Jaeoh Woo

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Boman and Hendrickson observed that one can solve linear systems in Laplacian matrices in time $\bigO{m^{3/2 + o (1)} \ln (1/\epsilon)}$ by preconditioning with the Laplacian of a low-stretch spanning tree. By examining the distribution of eigenvalues of the preconditioned linear system, we prove that the preconditioned conjugate gradient will actually solve the linear system in time $\softO{m^{4/3} \ln (1/\epsilon)}$.

Source: http://arxiv.org/abs/0903.2816v1

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Sep 23, 2013
09/13

by
G. Hector; E. Macías-Virgós; E. Sanmartín-Carbón

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Let $(M,\mathcal{F})$ be a foliated manifold. We prove that there is a canonical isomorphism between the complex of base-like forms $\Omega^*_b(M,\mathcal{F})$ of the foliation and the "De Rham complex" of the space of leaves $M/\mathcal{F}$ when considered as a "diffeological" quotient. Consequently, the two corresponding cohomology groups $H^*_b(M,\mathcal{F})$ and $H^*(M/\mathcal{F})$ are isomorphic.

Source: http://arxiv.org/abs/0903.2871v1

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Sep 21, 2013
09/13

by
A. Yamasaki; S. Imada; K. Takase; T. Muro; Y. Kato; H. Kobori; A. Sugimura; N. Umeyama; H. Sato; Y. Hara; N. Miyakawa; S. I. Ikeda

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We have investigated the electronic structures of newly discovered superconductor FeSe1-x by bulk-sensitive photoemission spectroscopy (PES). The large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF) and it decreases steeply toward EF . Compared with results of band structure calculations, narrowing the Fe 3d band width and the energy shift of the band toward EF are found, suggesting a mass enhancement due to the weak electron correlation effect. Meanwhile, Fe 2p...

Source: http://arxiv.org/abs/0902.3314v3

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Sep 23, 2013
09/13

by
Rainer M. Buchholz; Rainer Schödel; Andreas Eckart

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The goals of this work are to develop a new method to separate early and late type stellar components of a dense stellar cluster based on narrow band filters, to apply it to the central parsec of the GC, and to conduct a population analysis of this area. We use AO assisted observations obtained at the ESO VLT in the NIR H-band and 7 intermediate bands covering the NIR K-band. A comparison of the resulting SEDs with a blackbody of variable extinction then allows us to determine the presence and...

Source: http://arxiv.org/abs/0903.2135v2

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Sep 23, 2013
09/13

by
T. Fujita; M. B. A. Jalil; S. G. Tan

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A semi-classical description of the intrinsic spin-Hall effect (SHE) is presented which is relevant for a wide class of systems. A heuristic model for the SHE is developed, starting with a fully quantum mechanical treatment, from which we construct an intuitive expression for the spin-Hall current and conductivity. Our method makes transparent the physical mechanism which drives the effect, and unifies the SHE across several spintronic and optical systems. Finally, we propose an analogous...

Source: http://arxiv.org/abs/0903.2702v1

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Sep 23, 2013
09/13

by
Frans Snik

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Many objects on the sky exhibit a centrosymmetric polarization pattern, particularly in cases involving single scattering around a central source. Utilizing a novel liquid crystal device (the ``theta cell'') that transforms the coordinate system of linear polarization in an image plane from Cartesian to polar, the observation of centrosymmetric polarization patterns can be improved: instead of measuring Stokes Q and U on the sky, one only needs to measure Stokes Q' in the new instrument...

Source: http://arxiv.org/abs/0903.2734v1

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Sep 23, 2013
09/13

by
Y. J. Uemura

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Recent muon and neutron experiments on the new FeAs-based superconductors revealed phase diagrams characterized by first-order evolution from antiferromagnetic to superconducting states, and an inelastic magnetic resonance mode whose energy scales as $\sim 4 k_{B}T_{c}$. These features exhibit striking commonalities with cuprate, backyball, organic, and heavy-fermion superconductors as well as superfluid $^{4}$He.

Source: http://arxiv.org/abs/0903.2758v1

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Sep 23, 2013
09/13

by
L. R. Bedin; M. Salaris; G. Piotto; J. Anderson; I. R. King; S. Cassisi

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We use 14 orbits of ACS observations to reach the end of the white-dwarf cooling sequence in the globular cluster M4. Our photometry and completeness tests show that the end is located at magnitude m_F606W = 28.5+/-0.1, which implies an age of 11.6+/-0.6 Gyr (internal errors only). This is consistent with the age from fits to the main sequence turn-off (12.0+/-1.4 Gyr).

Source: http://arxiv.org/abs/0903.2839v1

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Sep 23, 2013
09/13

by
Alexander John; Andreas Schadschneider; Debashish Chowdhury; Katsuhiro Nishinari

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We report experimental results on unidirectional traffic-like collective movement of ants on trails. Our work is primarily motivated by fundamental questions on the collective spatio-temporal organization in systems of interacting motile constituents driven far from equilibrium. Making use of the analogies with vehicular traffic, we analyze our experimental data for the spatio-temporal organisation of the ants on the trail. From this analysis, we extract the flow-density relation as well as the...

Source: http://arxiv.org/abs/0903.2717v1

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Sep 23, 2013
09/13

by
Guo-Li Liu

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Topcolor-assisted technicolor (TC2) model predicts the existence of the top-pions and the CP-even top-Higgs with large flavor-changing couplings to the top quark, which at tree-level can mediate the top quark three-body decay t -> cb\bar{b}. In this work we study this decay, showing the dependence of the decay rate on the relevant TC2 parameters and comparing the results with the predictions in the minimal supersymmetric model. We find that the decay rate in the TC2 model is much larger than...

Source: http://arxiv.org/abs/0903.2619v1

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Sep 21, 2013
09/13

by
A. K. Kwasniewski

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The way to arrive at formula of zeta matrix for any graded posets with the finite set of minimal elements is delivered following the first reference. This is being achieved via adjacency and zeta matrix description of bipartite digraphs chains, the representatives of graded posets. The bipartite digraphs elements of such chains amalgamate to form corresponding cover relation graded poset digraphs with corresponding adjacency matrices being amalgamated throughout natural join as special adequate...

Source: http://arxiv.org/abs/0901.0155v2

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Sep 18, 2013
09/13

by
Martin Lorenz

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Let G be an affine algebraic group and let R be an associative algebra with a rational action of G by algebra automorphisms. We study the induced G-action on the spectrum Spec R of all prime ideals of R, viewed as a topological space with the Jacobson-Zariski topology, and on the subspace consisting of all rational ideals of R. Here, a prime ideal P of R is said to be rational if the extended centroid of R/P is equal to the base field. The main themes of the article are local closedness of...

Source: http://arxiv.org/abs/0809.5205v2

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Sep 23, 2013
09/13

by
Shirley Ho; Simon Dedeo; David Spergel

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We present a new method for detecting the missing baryons by generating a template for the kinematic Sunyaev-Zel'dovich effect. The template is computed from the product of a reconstructed velocity field with a galaxy field; we find that the combination of a galaxy redshift survey such as SDSS and a CMB survey such as ACT and PLANCK can detect the kSZ, and thus the ionized gas, at significant signal-to-noise. Unlike other techniques that look for hot gas or metals, this approach directly...

Source: http://arxiv.org/abs/0903.2845v1

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Sep 18, 2013
09/13

by
Franziska Synatschke; Georg Bergner; Holger Gies; Andreas Wipf

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We study supersymmetric quantum mechanics with the functional RG formulated in terms of an exact and manifestly off-shell supersymmetric flow equation for the effective action. We solve the flow equation nonperturbatively in a systematic super-covariant derivative expansion and concentrate on systems with unbroken supersymmetry. Already at next-to-leading order, the energy of the first excited state for convex potentials is accurately determined within a 1% error for a wide range of couplings...

Source: http://arxiv.org/abs/0809.4396v2

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Sep 22, 2013
09/13

by
Andreas Luscher; Andreas Laeuchli

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We study the field dependence of the antiferromagnetic spin-1/2 Heisenberg model on the square lattice by means of exact diagonalizations. In a first part, we calculate the spin-wave velocity, the spin-stiffness, and the magnetic susceptibility and thus determine the microscopic parameters of the low-energy long-wavelength description. In a second part, we present a comprehensive study of dynamical spin correlation functions for magnetic fields ranging from zero up to saturation. We find that...

Source: http://arxiv.org/abs/0812.3420v3

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Sep 23, 2013
09/13

by
M. Battaglia; L. Fletcher; A. O. Benz

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In the classical flare picture, hard X-ray emission from the chromosphere is succeeded by soft-X-ray emission from hot plasma in the flare loop, the soft X-ray emission being a direct consequence of the impact of the non-thermal particle beam. However, observations of events exist in which a pronounced increase in soft X-ray emission is observed minutes before the onset of the hard X-ray emission. Such pre-flare emission clearly contradicts the classical flare picture. For the first time, the...

Source: http://arxiv.org/abs/0903.2754v1

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Sep 23, 2013
09/13

by
Babak Vakili

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The effects of noncommutativity and deformed Heisenberg algebra on the evolution of a two dimensional minisuperspace quantum cosmological model are investigated.

Source: http://arxiv.org/abs/0903.2789v1

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Sep 22, 2013
09/13

by
Sergio Gomez; Pablo Jensen; Alex Arenas

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We present a reformulation of modularity that allows the analysis of the community structure in networks of correlated data. The new modularity preserves the probabilistic semantics of the original definition even when the network is directed, weighted, signed, and has self-loops. This is the most general condition one can find in the study of any network, in particular those defined from correlated data. We apply our results to a real network of correlated data between stores in the city of...

Source: http://arxiv.org/abs/0812.3030v2

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Sep 22, 2013
09/13

by
HERA-B Collaboration

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Inclusive doubly differential cross sections d^2\sigma_{pA}/dx_Fdp_T^2 as a function of Feynman-x (x_F) and transverse momentum (p_T) for the production of K^0_s, Lambda^0 and anti-Lambda^0 in proton-nucleus interactions at 920 GeV are presented. The measurements were performed by HERA-B in the negative x_F range (-0.12

Source: http://arxiv.org/abs/0812.0471v2

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Sep 23, 2013
09/13

by
A. Morozov; Sh. Shakirov

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The simplest partition function, associated with homogeneous symmetric forms S of degree r in n variables, is integral discriminant J_{n|r}(S) = \int e^{-S(x_1 ... x_n)} dx_1 ... dx_n. Actually, S-dependence remains the same if e^{-S} in the integrand is substituted by arbitrary function f(S), i.e. integral discriminant is a characteristic of the form S itself, and not of the averaging procedure. The aim of the present paper is to calculate J_{n|r} in a number of non-Gaussian cases. Using Ward...

Source: http://arxiv.org/abs/0903.2595v1

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Sep 23, 2013
09/13

by
Helmut Satz

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Quantum chromodynamics predicts that the interaction between its fundamental constituents, quarks and gluons, can lead to different states of strongly interacting matter, dependent on its temperature and baryon density. We first survey the possible states of matter in QCD and discuss the transition from a color-confining hadronic phase to a plasma of deconfined colored quarks and gluons. Next, we summarize the results from non-perturbative studies of QCD at finite temperature and baryon...

Source: http://arxiv.org/abs/0903.2778v1

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Sep 18, 2013
09/13

by
Hamid R. Molavian; Michel J. P. Gingras

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Despite a Curie-Weiss temperature $\theta_{\rm CW} \sim -14$ K, the Tb2Ti2O7 pyrochlore magnetic material lacks long range magnetic order down to at least $T^*\approx 50$ mK. It has recently been proposed that the low temperature collective paramagnetic or spin liquid regime of this material may be akin to a spin ice state subject to both thermal and quantum fluctuations $-$ a {\it quantum spin ice} (QSI) of sorts. Here we explore the effect of a magnetic field ${\bm B}$ along the $[111]$...

Source: http://arxiv.org/abs/0809.3477v2

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Sep 23, 2013
09/13

by
Cosmo Lupo; Vittorio Giovannetti; Stefano Mancini

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We introduce a general model for a lossy bosonic memory channel and calculate the classical and the quantum capacity, proving that coherent state encoding is optimal. The use of a proper set of collective field variables allows to unravel the memory, showing that the n-fold concatenation of the memory channel is unitarily equivalent to the direct product of n single-mode lossy bosonic channels.

Source: http://arxiv.org/abs/0903.2764v1

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Sep 21, 2013
09/13

by
Stephan Durr

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A Lie-algebra based recipe for smoothing gauge links in lattice field theory is presented, building on the matrix logarithm. With or without hypercubic nesting, this LOG/HYL smearing yields fat links which are differentiable w.r.t. the original ones. This is essential for defining UV-filtered ("fat link") fermion actions which may be simulated with a HMC-type algorithm. The effect of this smearing on the distribution of plaquettes and on the residual mass of tree-level O(a)-improved...

Source: http://arxiv.org/abs/0709.4110v2

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Sep 23, 2013
09/13

by
Wei-Hong Gao

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Strong optical and near-infrared (NIR) flares were discovered in the afterglow of GRB 080129. Their temporal behaviors, the sudden emergence and the quick disappearance, are rather similar to that of many X-ray flares (for instance, the giant flare of GRB 050502B). We argue that the optical/NIR flares following GRB 080129 are a low energy analogy of the X-ray flares and the most likely interpretation is the "late internal shock model". In this model, both the very sharp decline and...

Source: http://arxiv.org/abs/0903.2768v1

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Sep 23, 2013
09/13

by
Catalin D. Spataru; Mark S. Hybertsen; Steven G. Louie; Andrew J. Millis

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The Anderson model for a single impurity coupled to two leads is studied using the $GW$ approximation in the strong electron-electron interaction regime as a function of the alignment of the impurity level relative to the chemical potentials in the leads. We employ a non-equilibrium Green's function technique to calculate the electron self-energy, the spin density and the current as a function of bias across the junction. In addition we develop an expression for the change in the expectation...

Source: http://arxiv.org/abs/0903.2683v1

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Sep 23, 2013
09/13

by
S. T. Belinschi; D. Shlyakhtenko

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In this paper we give an analytic interpretation of free convolution of type B, introduced by Biane, Goodman and Nica, and provide a new formula for its computation. This formula allows us to show that free additive convolution of type B is essentially a re-casting of conditionally free convolution. We put in evidence several aspects of this operation, the most significant being its apparition as an 'intertwiner' between derivation and free convolution of type A. We also show connections...

Source: http://arxiv.org/abs/0903.2721v1

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Sep 23, 2013
09/13

by
Frans Snik; Radek Melich; Christoph Keller

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We present the design and the prototype of the Small Synoptic Second Solar Spectrum Telescope (S5T), which can autonomously measure scattering polarization signals on a daily basis with large sensitivity and accuracy. Its data will be used to investigate the nature of weak, turbulent magnetic fields through the Hanle effect in many lines. Also the relation between those fields and the global solar dynamo can be revealed by spanning the observations over a significant fraction of a solar cycle....

Source: http://arxiv.org/abs/0903.2730v1

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Sep 23, 2013
09/13

by
Daniel Allcock

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We prove the following: there are infinitely many finite-covolume (resp. cocompact) Coxeter groups acting on hyperbolic space H^n for every n < 20 (resp. n < 7). When n=7 or 8, they may be taken to be nonarithmetic. Furthermore, for 1 < n < 20, with the possible exceptions n=16 and 17, the number of essentially distinct Coxeter groups in H^n with noncompact fundamental domain of volume less than or equal to V grows at least exponentially with respect to V. The same result holds for...

Source: http://arxiv.org/abs/0903.0138v2

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Sep 23, 2013
09/13

by
J. -F. Desmurs; C. Codella; J. Santiago-Garcia; M. Tafalla; R. Bachiller

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We have performed observations of water maser emission towards a sample of low-mass protostars, in order to investigate the properties of jets associated with the earliest stages of star formation and their interaction with the surrounding medium. The main aim is to measure the absolute positions and proper motions of the H_2O spots in order to investigate the kinematics of the region from where the jet is launched. We imaged the protostars in the nearby region NGC 1333-IRAS 4 in the water...

Source: http://arxiv.org/abs/0903.2770v1

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Sep 21, 2013
09/13

by
Nikolay Gromov; Vladimir Kazakov; Pedro Vieira

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We present a set of functional equations defining the anomalous dimensions of arbitrary local single trace operators in planar N=4 SYM theory. It takes the form of a Y-system based on the integrability of the dual superstring sigma-model on the AdS_5xS^5 background. This Y-system passes some very important tests: it incorporates the full asymptotic Bethe ansatz at large length of operator L, including the dressing factor, and it confirms all recently found wrapping corrections. The recently...

Source: http://arxiv.org/abs/0901.3753v3

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Sep 22, 2013
09/13

by
Armin Lühr; Alejandro Saenz

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The stopping power of antiprotons in atomic and molecular hydrogen as well as helium was calculated in an impact-energy range from 1 keV to 6.4 MeV. In the case of H2 and He the targets were described with a single-active electron model centered on the target. The collision process was treated with the close-coupling formulation of the impact-parameter method. An extensive comparison of the present results with theoretical and experimental literature data was performed in order to evaluate...

Source: http://arxiv.org/abs/0812.5058v2

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41

Sep 18, 2013
09/13

by
Yonina C. Eldar

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A traditional assumption underlying most data converters is that the signal should be sampled at a rate exceeding twice the highest frequency. This statement is based on a worst-case scenario in which the signal occupies the entire available bandwidth. In practice, many signals are sparse so that only part of the bandwidth is used. In this paper, we develop methods for low-rate sampling of continuous-time sparse signals in shift-invariant (SI) spaces, generated by m kernels with period T. We...

Source: http://arxiv.org/abs/0806.3332v2

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42

Sep 19, 2013
09/13

by
Andy T. S. Wan; M. H. S. Amin; Shannon X. Wang

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We study the effect of an environment consisting of noninteracting two level systems on Landau-Zener transitions with an interest on the performance of an adiabatic quantum computer. We show that if the environment is initially at zero temperature, it does not affect the transition probability. An excited environment, however, will always increase the probability of making a transition out of the ground state. For the case of equal intermediate gaps, we find an analytical upper bound for the...

Source: http://arxiv.org/abs/cond-mat/0703085v3

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36

Sep 23, 2013
09/13

by
D. Speer; R. Eichhorn; P. Reimann

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We consider an overdamped Brownian particle, exposed to a two-dimensional, square lattice potential and a rectangular ac-drive. Depending on the driving amplitude, the linear response to a weak dc-force along a lattice symmetry axis consist in a mobility in basically any direction. In particular, motion exactly opposite to the applied dc-force may arise. Upon changing the angle of the dc-force relatively to the square lattice, the particle motion remains predominantly opposite to the dc-force....

Source: http://arxiv.org/abs/0903.2736v1

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Sep 23, 2013
09/13

by
N. N. Nikolaev; V. R. Zoller

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One of the well known effects of the asymptotic freedom is splitting of the leading-$\log$ BFKL pomeron into a series of isolated poles in complex angular momentum plane. Following our earlier works we explore the phenomenological consequences of the emerging BFKL-Regge factorized expansion for the small-$x$ charm ($F_2^c$) and beauty ($F_{2}^{b}$) structure functions of the proton. As we found earlier,the color dipole approach to the BFKL dynamics predicts uniquely decoupling of subleading...

Source: http://arxiv.org/abs/0903.2729v1

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Sep 17, 2013
09/13

by
Tobias Salger; Gunnar Ritt; Carsten Geckeler; Sebastian Kling; Martin Weitz

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We report on experiments studying transport properties of an atomic Bose-Einstein condensate in an optical lattice of spatial period $\lambda/2n$, where $n$ is an integer, realized with the dispersion of multiphoton Raman transitions. We observe Bloch oscillations, as a clear effect of quantum transport, in the sub-wavelength scale periodicity lattice. The unusually strong localisation of atoms is evident from the measured effective mass. Future prospects of the novel lattice structures are...

Source: http://arxiv.org/abs/0711.1772v3