September 2003 arXiv papers — page 17

N. Drichko, K. Petukhov, M. Dressel, O. Bogdanova

The polarized reflectivity of $β^{\prime\prime}$-(BEDO-TTF)$_5$[CsHg(SCN)$_4$]$_2$ is studied in the infrared range between 60 cm-1 and 6000 cm-1 from room temperature down to 10 K. Already at T=300 K a pseudogap in the optical conductivity is present of about 300 cm-1; the corresponding maximum in the spectrum shifts to lower frequencies as the temperature

J. Zaanen, Z. Nussinov, S. I. Mukhin

The generalization of the Nelson-Halperin-Young theory of 2D melting to the dynamical 2+1D quantum case is presented. The bosonic quantum crystal dualizes in superfluids or superconductors exhibiting nematic liquid crystalline orders, corresponding with bose condensates of dislocations exhibiting a dual shear Meissner-Higgs mechanism. The topologically order

M. D. Girardeau, M. Olshanii

A K-matrix for waveguide confined spin-polarized fermionic atoms recently computed by Granger and Blume is identified, in the low-energy domain, with a contact condition for one-dimensional (1D) spinless fermions. Difficulties in consistently formulating the contact conditions in terms of interaction potentials are discussed and a rigorous alternative variat

J. Linden, T. Shimada, T. Motohashi, H. Yamauchi

Double perovskite, (Sr1-xNdx)2FeMoO6, was doped with electrons through partial substitution of divalent Sr by trivalent Nd (0 < x < 0.2). The Fe valence and the degree of B-site order were probed by 57Fe Mossbauer spectroscopy. Replacing Sr by Nd increased the fraction of Fe and Mo atoms occupying wrong sites, i.e. antisite disorder. It had very little effec

T. Shimada, J. Nakamura, T. Motohashi, H. Yamauchi

Here we show that the B-site cation (Fe/Mo) ordering in the double-perovskite magnetoresistor, Sr2FeMoO6, is controlled by either kinetics or thermal equilibrium depending on the temperature range. In order to enhance the ordering, long synthesis periods at moderate temperatures are thus required. Employment of a special oxygen-getter-controlled low-O2-press

J. J. Alonso, J. F. Fernandez

We report results from Monte Carlo simulations of systems of magnetic dipoles that relax through quantum tunneling, much as Fe_8 crystals at very low temperature.For short times, a hole develops in suitably defined magnetic field pseudo--distributions, which matches the shape of the tunnel window (TW). Much later, ordinary field distributions P(h) develop si

P. Sinjukow, W. Nolting

It is shown that the spectacular metal-insulator transition in Eu-rich EuO can be simulated within an extended Kondo lattice model. The different orders of magnitude of the jump in resistivity in dependence on the concentration of oxygen vacancies as well as the low-temperature resistance minimum in high-resistivity samples are reproduced quantitatively. The

H. Gutmann, F. K. Wilhelm, W. M. Kaminsky, S. Lloyd

With the growing efforts in isolating solid-state qubits from external decoherence sources, the origins of noise inherent to the material start to play a relevant role. One representative example are charged impurities in the device material or substrate, which typically produce telegraph noise and can hence be modelled as bistable fluctuators. In order to d

W. De Roeck, T. Jacobs, C. Maes, K. Netocny

We introduce a unitary dynamics for quantum spins which is an extension of a model introduced by Mark Kac to clarify the phenomenon of relaxation to equilibrium. When the number of spins gets very large, the magnetization satisfies an autonomous equation as function of time with exponentially fast relaxation to the equilibrium magnetization as determined by

J. -H. Kim, K. -I. Goh, B. Kahng, D. Kim

In complex systems, responses to small perturbations are too diverse to predict how much they would be definitely, and then such diverse responses can be predicted in a probabilistic way. Here we study such a problem in scale-free networks, for example, the diameter changes by the deletion of each node for various in silico and real world scale-free networks

Markus J. Aschwanden, C. J. Schrijver, A. R. Winebarger, H. P. Warren

Recent observations with TRACE reveal that the time delay between the appearance of a cooling loop in different EUV temperature filters is proportional to the loop length, dt_12 ~ L. We model this cooling delay in terms of radiative loss and confirm this linear relationship theoretically. We derive an expression that can be used to constrain the coronal iron

Markus J. Aschwanden

Recent observations show a variety of oscillation modes in the corona. Early non-imaging observations in radio wavelengths showed a number of fast-period oscillations in the order of seconds, which have been interpreted as fast sausage mode oscillations. TRACE observations from 1998 have for the first time revealed the lateral displacements of fast kink mode

M. Sikora, M. C. Begelman, P. Coppi, D. Proga

We propose a gamma-ray burst scenario involving relativistic jets dominated by Poynting flux with alternating toroidal magnetic fields. Such a structure may arise naturally if the jet is formed and powered by the accretion flow in the core of a collapsar. We conjecture that the polarity of the toroidal magnetic field changes randomly due to hydromagnetic tur

M. Sako, S. M. Kahn, F. Paerels, D. A. Liedahl

A review of spectroscopic results obtained from Chandra High Energy Transmission Grating Spectrometer and XMM-Newton Reflection Grating Spectrometer observations of several wind-fed high-mass X-ray binaries (HMXBs) is presented. These observations allow us to study the structure of the stellar wind in more detail and provide, for the first time, a dyanmical

Harvey B. Richer, Rodrigo Ibata, Gregory G. Fahlman, Mark Huber

A young and undermassive white dwarf has been identified as the possible companion to the millisecond pulsar PSR B1620-26 in Messier 4. This association is important as it then helps constrain the mass of the third body in the system to be of order a few times that of Jupiter. The presence of this planet in M4 has critical implications for planetary formatio

Markus J. Aschwanden, David Alexander, Marc DeRosa

The &#34;Frequency-Agile Solar Radiotelescope&#34; (FASR) litteraly opens up a new dimension in addition to the 3D Euclidian geometry: the frequency dimension. The 3D geometry is degenerated to 2D in all images from astronomical telescopes, but the additional frequency dimension allows us to retrieve the missing third dimension by means of physical modeling.

Lucio Mayer, Ben Moore

We show that a global relation between baryonic mass and virial velocity can be constructed from the scale of dwarf galaxies up to that of rich galaxy clusters. The slope of this relation is close to that expected if dark matter halos form in the standard hierarchical cosmogony and capture a universal baryon fraction, once the details of halo structure and t

Markus J. Aschwanden, Thomas R. Metcalf, Sam Krucker, Jun Sato

We compare the photometric accuracy of spectra and images in flares observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI)}spacecraft. We test the accuracy of the photometry by comparing the photon fluxes obtained in different energy ranges from the spectral-fitting software SPEX with those fluxes contained in the images reconstructed with

Michael Eracleous, Jules P. Halpern

We report accurate redshifts of 110 active galaxies (mostly radio-loud objects at z<0.4) observed in the course of a survey to find broad, double-peaked emission lines. These redshifts are measured from the narrow emission lines of these objects and are accurate to at least one part in 10^4 . For each object we determine a redshift from high- and low-ionizat

L. Chemin, V. Cayatte, C. Balkowski, P. Amram

We present results from an ongoing survey dedicated to the ionized gas kinematics of Virgo cluster spiral galaxies using Fabry-Perot interferometry. Our goal is to study the environmental effects on galaxy evolution in the Virgo cluster. We report here on the Halpha distribution map and velocity field of NGC 4438, the prototype of an interacting galaxy near

J. A. Stevens, R. J. Ivison, J. S. Dunlop, Ian R. Smail

The most massive galaxies in the present-day Universe are found to lie in the centres of rich clusters. They have old, coeval stellar populations suggesting that the bulk of their stars must have formed at early epochs in spectacular starbursts - luminous phenomena at submillimetre wavelengths. The most popular model of galaxy formation predicts that these g

T. N. Rengarajan, Y. D. Mayya

We have computed the time evolution of bolometric, far-infrared, Halpha line, ultraviolet (both intrinsic and escaping the star forming region) and the nonthermal radio continuum luminosities for continuous and constant star formation. The luminosity rises to a plateau value and declines after the termination of starburst, but only gradually. The time evolut

Markus J. Aschwanden, Valery M. Nakariakov, Victor F. Melnikov

A recent study by Nakariakov et al. pointed out that the dispersion relation of MHD sausage mode oscillations has been incorrectly applied to coronal loops, neglecting the highly dispersive nature of the phase speed and the long-wavelength cutoff of the wave number. In the light of these new insights we revisit previous observations that have been interprete

A. Fernandez-Soto

The REM telescope is being deployed these very days at the La Silla Observatory in Chile, and will be fully operational by the beginning of 2004. It is a very fast-slewing robotized telescope, endowed with optical and near-infrared capabilities, designed with the primary objective of performing rapid follow-up of GRB events. One of the key issues will be the

T. Yamamoto

We measured the Cerenkov signal fluctuations in the water tanks of the Pierre Auger Observatory. Two stations located near the center of the 32-tank Engineering Array separated by 11 m were used for the purpose. At this separation the stations sample nearly the same region of the air shower. Sources of the signal fluctuations are discussed.

Federico Piazza, Christian Marinoni

According to the gravitational suppression (GraS) hypothesis the gravitational interaction between exotic (dark) and standard (visible) matter is suppressed below the kpc scales. We review the phenomenological motivations at the basis of this idea and its formal implementation by means of a Yukawa contribution to the usual Newtonian potential. We also discus

Lee Hartmann

Protostellar core formation is probably much more dynamic, and magnetic fields are probably much less important, than has been previously assumed in the standard model of low-mass star formation. This revised picture has important consequences: it is easier to understand the observed rapidity of star formation in molecular clouds; cores are more likely to ha

G. J. Harris, A. E. Lynas-Gray, S. Miller, J. Tennyson

H3+ has been shown (Lenzuni et al. 1991, ApJS, 76, 759) to be the dominant positive ion, in a zero metallicity gas at low temperature and intermediate to high density. It therefore affects both the number of free electrons and the opacity of the gas. The most recent H3+ partition function (Neale and Tennyson, 1995, ApJ, 454, L169) is an order of magnitude la

Andreas Just, Pau Amaro-Seoane

Highly condensed gaseous objects with masses larger than 5x10^4 M_sun are called super-massive stars. In the quasistationary contraction phase, the hydrostatic equilibrium is determined by radiation pressure and gravitation. The global structure is that of an n=3 polytrope at the stability limit. Small relativistic corrections for example can initiate a free

P. Jean, J. Knoedlseder, V. Lonjou, M. Allain

We report the first measurements of the 511 keV line emission from the Galactic Centre (GC) region performed with the spectrometer SPI on the space observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory). Taking into account the range of spatial distribution models which are consistent with the data, we derive a flux of $9.9^{+4.7}_{-2.1} \tim

P. Bergeron, G. Fontaine, M. Billeres, S. Boudreault

We report the discovery of two new ZZ Ceti pulsators, LP 133-144 and HE 1258+0123, selected on the basis of model atmosphere fits to optical spectroscopic data. The atmospheric parameters for LP 133-144, Teff = 11,800 +/- 200 K and log g = 7.87 +/- 0.05, and for HE 1258+0123, Teff = 11,410 +/- 200 K and log g = 8.04 +/- 0.05, place them within the empirical

Martin Kilbinger

We present simulations of a cosmic shear survey and show how the survey geometry influences the accuracy of determination of cosmological parameters. We numerically calculate the full covariance matrices of the two-point statistics ξ_+, ξ_- and <Map^2> and use maximum likelihood and Fisher matrix analyses in order to derive expected constraints on the cosmol

Alexis Brandeker

New high-resolution adaptive optics systems provide an unprecedentedly detailed view of nearby star forming regions. In particular, young nearby T Tauri stars can be probed at much smaller physical scales (a few AU) than possible just a decade ago (several tens of AU). Of major importance is closing the sensitivity gap between imaging and spectral surveys fo

A. Coc, E. Vangioni-Flam, P. Descouvemont, A. Adahchour

We improve Standard Big Bang Nucleosynthesis (SBBN) calculations taking into account new nuclear physics analyses (Descouvemont et al. 2003). Using a Monte-Carlo technique, we calculate the abundances of light nuclei versus the baryon to photon ratio.The results concerning omegab are compared to relevant astrophysical and cosmological observations. Consisten

L. Schmidtobreick, C. Tappert, A. Bianchini, R. E. Mennickent

We present optical spectroscopy and multi colour photometry of the old nova V840 Oph. We rediscovered the nova based on its position in the colour--colour diagrams. It stands out as a very blue object with an additional red component. We present the first optical spectroscopy of this candidate and confirm its nova character. Furthermore, V840\,Oph has been f

Martin Bojowald

Quantum gravity has matured over the last decade to a theory which can tell in a precise and explicit way how cosmological singularities of general relativity are removed. A branch of the universe &#34;before&#34; the classical big bang is obtained which is connected to ours by quantum evolution through a region around the singularity where the classical spa

Raffaella Morganti, Tom Oosterloo, Clive Tadhunter, Bjorn Emonts

The study of the optical continuum of radio galaxies shows that about 30% have a young stellar population component. Among them are the most far-IR bright radio galaxies. A further indication of the relatively gas rich environment of these galaxies (possibly related to the recent merger from which they originate) is the high fraction being detected in HI. He

David T. F Weldrake, Penny D Sackett, Terry J Bridges

We present a short progress report of a comprehensive search for variability in the globular cluster 47 Tucanae. Using the MSSSO 40&#39;&#39; telescope and a combined V+R filter, we are searching for variability across a 52x52&#39; field centered on the cluster. The main aim is to search for transiting &#39;Hot Jupiter&#39; planets, the results of which are

A. Deur

The non-abelian symmetry of a lagrangian invalidates the principle of superposition for the field described by this lagrangian. A consequence in QCD is that non-linear effects occur, resulting in the quark-quark linear potential that explains the quark confinement, the quarkonia spectra or the Regge trajectories. Following a parallel between QCD and gravitat

Jg. Fischera, R. J. Tuffs, H. J. Voelk

Detailed models are presented for the late epoch mid infrared (MIR) emission from collisionally heated grains in the shocked circumstellar gas around SN 1987A. Thermal dust emission from a region of moderate density interior to the thick inner ring seen with the Hubble Space Telescope (HST) is found to be a natural explanation for the MIR spectral energy dis

Joerg Fischera, Michael A. Dopita, Ralph S. Sutherland

The empirical reddening function for starburst galaxies generated by Calzetti and her co-workers has proven very successful, and is now used widely in the observational literature. Despite its success, however, the physical basis for this extinction law, or more correctly, attenuation law remains weak. Here we provide a physical explanation for the Calzetti

Markus J. Aschwanden, Richard W. Nightingale, Jesse Andries, Marcel Goossens

One of the proposed damping mechanisms of coronal (transverse) loop oscillations in the kink-mode is resonant absorption as a result of the Alfven speed variation at the outer boundary of coronal loops. Analytical expressions for the period and damping time exist for loop models with thin non-uniform boundaries. Here we measure the thickness of the non-unifo

R. Casana

We present a non--perturbative study of the (1+1)--dimensional massless Thirring model by using path integral methods. The regularization ambiguities -coming from the computation of the fermionic determinant- allow to find new solution types for the model. At quantum level the Ward identity for the 1PI 2-point function for the fermionic current separates suc

D. Q. Lamb, G. R. Ricker, J-L. Atteia, C. Barraud

The HETE-2 mission has been highly productive. It has observed more than 250 GRBs so far. It is currently localizing 25 - 30 GRBs per year, and has localized 43 GRBs to date. Twenty-one of these localizations have led to the detection of X-ray, optical, or radio afterglows, and as of now, 11 of the bursts with afterglows have known redshifts. HETE-2 has conf

Christopher J. Burke, Marc H. Pinsonneault, Alison Sills

We explore the sensitivity in open cluster ages obtained by the lithium depletion boundary (LDB) technique to the stellar model input physics. The LDB age technique is limited to open clusters with ages ranging from 20 to 200 Myr. Effective 1-sig errors in the LDB technique due to uncertain input physics are roughly 3% at the oldest age increasing to 8% at t

A. F. Ferrari, H. O. Girotti, M. Gomes, A. Yu. Petrov

Commutative supersymmetric Yang-Mills is known to be renormalizable for ${\cal N} = 1, 2$, while finite for ${\cal N} = 4$. However, in the noncommutative version of the model (NCSQED$_4$) the UV/IR mechanism gives rise to infrared divergences which may spoil the perturbative expansion. In this work we pursue the study of the consistency of NCSQED$_4$ by wor

I. R. Klebanov, J. Maldacena, N. Seiberg

We propose that the double scaling behavior of the unitary matrix models, and that of the complex matrix models, is related to type 0B and 0A fermionic string theories. The particular backgrounds involved correspond to $\hat c<1 $ matter coupled to super-Liouville theory. We examine in detail the $\hat c=0$ or pure supergravity case, which is related to the

s Eye Collaboration

Several proposed source models for Ultra-High Energy Cosmic Rays (UHECRs) consist of dipole distributions oriented towards major astrophysical landmarks such as the galactic center, M87, or Centaurus A. We use a comparison between real data and simulated data to show that the HiRes-I monocular data for energies above 10^{18.5} eV is, in fact, consistent with

Aneesh V. Manohar

Soft-collinear effective theory (SCET) is used to sum Sudakov double-logarithms in the x ->1 endpoint region for the deep inelastic scattering structure function. The calculations are done in both the target rest frame and the Breit frame. The separation of scales in the effective theory implies that the anomalous dimension of the SCET current is linear in l

Richard R. Silbar, Sanjay Reddy

Calculating the structure of white dwarf and neutron stars would be a suitable topic for an undergraduate thesis or an advanced special topics or independent study course. The subject is rich in many different areas of physics accessible to a junior or senior physics major, ranging from thermodynamics to quantum statistics to nuclear physics to special and g

Boris Kors, Pran Nath

We consider a generic scenario of spontaneous breaking of supersymmetry in the hidden sector within N=1 supersymmetric orientifold compactifications of type II string theories with D-branes that support semi-realistic chiral gauge theories. The soft breaking terms in the visible sector of the models are computed in a standard way without specifying the break

Ali H. Chamseddine

We show that it is possible to formulate gravity with a complex vierbein based on SL(2,C) gauge invariance. The proposed action is a four-form where the metric is not introduced but results as a function of the complex vierbein. This formulation is based on the first order formalism. The novel feature here is that integration of the spin-connection gauge fie

D. Q. Lamb, T. Q. Donaghy, C. Graziani

HETE-2 has provided strong evidence that the properties of X-Ray Flashes (XRFs) and GRBs form a continuum, and therefore that these two types of bursts are the same phenomenon. We show that both the structured jet and the uniform jet models can explain the observed properties of GRBs reasonably well. However, if one tries to account for the properties of bot

M. Gilfanov

Using results of Chandra observations of old stellar systems in eleven nearby galaxies of various morphological types and the census of LMXBs in the Milky Way, we study the population of low mass X-ray binaries and their relation to the mass of the host galaxy. We show that the azimuthally averaged spatial distribution of the number of LMXBs and, in the majo

Tom Chou

We explore and quantify the physical and biochemical mechanisms that may be relevant in the regulation of translation. After elongation and detachment from the 3&#39; termination site of mRNA, parts of the ribosome machinery can diffuse back to the initiation site, especially if it is held nearby, enhancing overall translation rates. The elongation steps of

T. Sakamoto, D. Q. Lamb, C. Graziani, T. Q. Donaghy

We report HETE-2 WXM/FREGATE observations of the X-ray flash, XRF 020903. This event was extremely soft: the ratio log(S_X/S_gamma) = 0.7, where S_X and S_gamma are the fluences in the 2-30 and 30-400 keV energy bands, is the most extreme value observed so far by HETE-2. In addition, the spectrum has an observed peak energy E^{obs}_{peak} < 5.0 keV (99.7 % p

Ashok Das, J. Frenkel, S. H. Pereira, J. C. Taylor

We quantize non-commutative Maxwell theory canonically in the background field gauge for weak and slowly varying background fields. We determine the complete basis for expansion under such an approximation. As an application, we derive the Wigner function which determines the leading order high temperature behavior of the perturbative amplitudes of non-commu

D. Karasik, C. Sahabandu, P. Suranyi, L. C. R. Wijewardhana

An approximation method to study the properties of a small black hole located on the TeV brane in the Randall-Sundrum type I scenario is presented. The method enables us to find the form of the metric close to the matter distribution when its asymptotic form is given. The short range solution is found as an expansion in the ratio between the Schwarzschild ra

Igor Kondrashuk

We consider a particular solution to Slavnov-Taylor identity in four-dimensional supergravity. The consideration is performed for pure supergravity, no matter superfields are included. The solution is obtained by inserting dressing functions into ghost part of the classical action for supergravity.As a consequence, physical part of the effective action is lo

Andrew R. King

Chandra observations of the Cartwheel galaxy reveal a population of ultraluminous X-ray sources (ULXs) with lifetimes < 10^7 yr associated with a spreading wave of star formation which began some 3 x 10^8 yr ago. A population of high-mass X-ray binaries provides a simple model: donor stars of initial masses M_2 > 15 Msun transfer mass on their thermal timesc

F. Karsch, C. R. Allton, S. Ejiri, S. J. Hands

We determine the location of the second order endpoint of the line of first order chiral phase transition in 3-flavor QCD at vanishing chemical potential. Using Ferrenberg-Swendsen reweighting for two values of the quark mass we determine the dependence of the transition line on the chemical potential and locate the chiral critical point. For both quantities

Massimo D&#39;Elia, Maria-Paola Lombardo

We discuss the imaginary chemical potential approach to the study of QCD at nonzero temperature and density, present results for the four flavor model in the different phases and show that this method is ideally suited for a comparison between lattice data and phenomenological models.

Ulf H. Danielsson, Martin E. Olsson

We discuss thermalization in de Sitter space and argue, from two different points of view, that the typical time needed for thermalization is of order $R^{3}/l_{pl}^{2}$, where $R$ is the radius of the de Sitter space in question. This time scale gives plenty of room for non-thermal deviations to survive during long periods of inflation. We also speculate in

Marc Sher, Ismail Turan

The experimental discovery of large nu_mu-nu_tau mixing indicates that analogous mixing in the charged lepton sector could be substantial. We consider the possibility that if a high intensity muon beam, perhaps at the early stages of a muon or neutrino factory, strikes a nuclear target, then conversion of some of the muons into tau leptons could occur (simil

Kim Louis, Claudius Gros

Recently, the stochastic series expansion (SSE) has been proposed as a powerful MC-method, which allows simulations at low $T$ for quantum-spin systems. We show that the SSE allows to compute the magnetic conductance for various one-dimensional spin systems without further approximations. We consider various modifications of the anisotropic Heisenberg chain.

Elisa Nespoli, Tomaso Belloni, Jeroen Homan, Jon M. Miller

We report the results of an observation with the Rossi X-ray Timing Explorer of the black hole candidate GX 339-4 during its 2002/2003 outburst. This observation took place during a spectral transition from the hard to the soft state. A strong (6% rms) transient quasi-periodic oscillation (QPO) appears suddenly in the power density spectrum during this obser

F. Bazzocchi, S. Bertolini, M. Fabbrichesi, M. Piai

We present a complete analysis of the fermion masses and mixing matrices in the framework of the little flavon model. In this model textures are generated by coupling the fermions to scalar fields, the little flavons, that are pseudo-Goldstone bosons of the breaking of a global SU(6) symmetry. The Yukawa couplings arise from the vacuum expectation values of

Scott T. Kay

The entropy of the intracluster medium at large radii has been shown recently to deviate from the self-similar scaling with temperature. Using N-body/hydrodynamic simulations of the LCDM cosmology, we demonstrate that this deviation is evidence that feedback processes are important in generating excess entropy in clusters. While radiative cooling increases t

Alberto Maurizi, Annalisa Griffa, Pierre-Marie Poulain, Francesco Tampieri

The properties of mesoscale Lagrangian turbulence in the Adriatic Sea are studied from a drifter data set spanning 1990-1999, focusing on the role of inhomogeneity and nonstationarity. A preliminary study is performed on the dependence of the turbulent velocity statistics on bin averaging, and a preferential bin scale of 0.25 is chosen. Comparison with indep

Steffen Hein

Dual scattering channel schemes extend the transmission line matrix numerical method (JOHNS&#39; TLM algorithm) in two directions. For one point, transmission line links are replaced by abstract scattering channels in terms of paired distributions (characteristic impedances are thus neither needed, nor in general defined, e.g.). In the second place, non-triv

Jon Loveday

We measure the redshift-dependent luminosity function and the comoving radial density of galaxies in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1). Both measurements indicate that the apparent number density of bright galaxies increases by a factor ~3 as redshift increases from z=0 to z=0.3. This result is robust to the assumed cosmology, to the det

Martin Schvellinger

We obtain spinning and rotating closed string solutions in AdS_5 \times T^{1,1} background, and show how these solutions can be mapped onto rotating closed strings embedded in configurations of intersecting branes in type IIA string theory. Then, we discuss spinning closed string solutions in the UV limit of the Klebanov-Tseytlin background, and also propert

Katsusada Morita

It is pointed out that the usual $θ$-algebra assumed for non-commuting coordinates is not $P$- and $T$-invariant, unless one {\it formally} transforms the non-commutativity parameter $θ^{μν}$ in an appropriate way. On the other hand, the Lorentz-covariant DFR algebra, which `relativitizes&#39; the $θ$-algebra by replacing $θ^{μν}$ with a second-rank antisymm

Changhyun Ahn, Yutaka Ookouchi

In N=1 supersymmetric SO(N)/USp(2N) gauge theories with the tree-level superpotential W(Φ) that is an arbitrary polynomial of the adjoint matter Φ, the massless fluctuations about each quantum vacuum are described by U(1)^n gauge theory. By turning on the parameters of W(Φ) to the special values, the singular vacua where the additional fields become massless

S. Munier, R. Peschanski

We show the relevance of the nonlinear Fisher and Kolmogorov-Petrovsky- Piscounov (KPP) equation to the problem of high energy evolution of the QCD amplitudes. We explain how the traveling wave solutions of this equation are related to geometric scaling, a phenomenon observed in deep-inelastic scattering experiments. Geometric scaling is for the first time s

Nayantara Gupta

The clustering of ultra high energy cosmic ray events suggests that they have originated from compact sources. One of the possible physical mechanisms by which ultra high energy nuclei reach the Earth from far away astrophysical sources (quasars or BL Lac objects) evading the Greisen-Zatsepin-Kuzmin (GZK) cut-off is by violation of Lorentz invariance. Assumi

Katsusada Morita, Yoshitaka Okumura, Eizou Umezawa

It is shown that the one-loop two-point amplitude in {\it Lorentz-invariant} non-commutative (NC) $ϕ^3$ theory is finite after subtraction in the commutative limit and satisfies the usual cutting rule, thereby eliminating the unitarity problem in Lorentz-non-invariant NC field theory in the approximation considered.

Tomo Munehisa, Yasuko Munehisa

We apply a recently developed stochastic method to the Shastry-Sutherland model on 4x4 and 8x8 lattices. This method, which we call the Stochastic State Selection Method here, enables us to evaluate expectation values of powers of the Hamiltonian with very limited number of states. In this paper we first apply it to the 4x4 Shastry-Sutherland system, where o

Sanjay Gupta, Shreekantha Sil, Bibhas Bhattacharyya

We have studied a Hubbard ring with alternating site potentials for half filling in presence of a magnetic flux. Using a mean field approach we have calculated the conductivity of such a ring at low and high temperatures. The interplay of correlation, the polarizing field and the chemical modulation in the site potentials tune the conductivity in an interest

T. Bhattacharya, G. T. Fleming, G. Kilcup, R. Gupta

We present preliminary results of weak matrix elements relevant to CP violation calculated using the HYP (II) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the $g^2$ corrections included. The main results include both $ΔI = 3/2$ and $ΔI = 1/2

Hidenori Fukaya, Tetsuya Onogi

We present a numerical study of the massive two-flavor QED in two dimensions with the gauge action proposed by Lüscher, which allows only ``admissible&#39;&#39; gauge fields. We find that the admissibility condition does not allow any topology changes by the local updation in Hybrid Monte Carlo algorithm so that the configurations in each topological sector

Liam Wagner, Joshua Ross, Hugh Possingham

We consider the optimal spacing between marine reserves for maximising the viability of a species occupying a reserve network. The closer the networks are placed together, the higher the probability of colonisation of an empty reserve by an occupied reserve, thus increasing population viability. However, the closer the networks are placed together, the highe

D. Acosta

We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 ${pb}^{-1}$ of \ppb collisions at $\sqrt{s}$ = 1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a $3+1+n$-dimensional K

Matt Visser

In this article I present a simple Newtonian heuristic for deriving a weak-field approximation for the spacetime geometry of a point particle. The heuristic is based on Newtonian gravity, the notion of local inertial frames [the Einstein equivalence principle], plus the use of Galilean coordinate transformations to connect the freely falling local inertial f

Richard A Mould

When a weak decay competes with a strong decay in a 3-level atom, some mechanism is necessary to occasionally stop the strong decay so the weak decay can be completed. Rule (4) provides that mechanism. Using this rule, a weak photon is emitted at the correct time for both the V and L configurations, as well as for the two cascade configurations. Key Words: o

Richard A Mould

New rules are proposed to govern the collapse of a wave function during measurement. These rules apply with or without an observer in the system. They overcome an absurdity that was previous found when an objective state reduction is combined with an observer-based state reduction. Key Words: brain states, conscious observer, detector, measurement, florescen

Lov Grover, Terry Rudolph

Quantum search is a technique for searching N possibilities in only O(sqrt(N)) steps. It has been applied in the design of quantum algorithms for several structured problems. Many of these algorithms require significant amount of quantum hardware. In this paper we observe that if an algorithm requires O(P) hardware, it should be considered significant if and

Eduardo D. Sontag

This note provides a theorem showing, under suitable technical assumptions, that if a system S adapts to a class of external signals U, in the sense of egulation against disturbances or tracking signals in U, then S must ecessarily contain a subsystem which is capable of generating all the signals in U. It is not assumed that regulation is robust, nor is the

David Angeli, Eduardo D. Sontag

This paper studies the emergence of multi-stability and hysteresis in those systems that arise, under positive feedback, starting from monotone systems with well-defined steady-state responses. Such feedback configurations appear routinely in several fields of application, and especially in biology. Characterizations of global stability behavior are stated i

David Angeli, Eduardo D. Sontag

Monotone systems constitute one of the most important classes of dynamical systems used in mathematical biology modeling. The objective of this paper is to extend the notion of monotonicity to systems with inputs and outputs, a necessary first step in trying to understand interconnections, especially including feedback loops, built up out of monotone compone

Zoran Pavlovic, Björn O. Roos, Robin Côté, H. R. Sadeghpour

We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to buffer-gas and magneto-optical cooling of chromium atoms. We calculate ab initio potential energy curves for Cr2 and the van der Waals coefficient C6, and construct int

K. L. Ekinci, Y. T. Yang, M. L. Roukes

Nanomechanical resonators can now be realized that achieve fundamental resonance frequencies exceeding 1 GHz, with quality factors (Q) in the range 1,000 - 100,000. The minuscule active masses of these devices, in conjunction with their high Qs, translate into unprecedented inertial mass sensitivities. This makes them natural candidates for a variety of mass

F. Paesani, R. E. Zillich, K. B. Whaley

We determine the structure and energetics of complexes of the linear OCS molecule with small numbers of para-hydrogen molecules, N=1-8, using zero temperature quantum Monte Carlo methods. Ground state calculations are carried out with importance-sampled rigid body diffusion Monte Carlo (IS-RBDMC) and excited state calculations with the projection operator im

W. Bietenholz, S. Capitani, T. Chiarappa, M. Hasenbusch

Quantum Chromo Dynamics is considered in a setup where the light mesons are squeezed into unphysically small boxes. We show how such a situation can be used to determine the couplings of the low energy chiral Lagrangian from lattice simulations, applying chirally invariant formulations of lattice fermions.

Hong Qian

Based on a thermodynamic analysis of the kinetic model for the protein phosphorylation-dephosphorylation cycle, we study the ATP (or GTP) energy utilization of this ubiquitous biological signal transduction process. It is shown that the free energy from hydrolysis inside cells, $ΔG$ (phosphorylation potential), controls the amplification and sensitivity of t

Bogdan Mihaila

We review the basics of the coupled-cluster expansion formalism for numerical solutions of the many-body problem, and we outline the principles of an approach directed towards an adequate inclusion of continuum effects in the associated single-energy spectrum. We illustrate our findings by considering the simple case of a single-particle quantum mechanics pr

Ben-Wei Zhang, Enke Wang, Xin-Nian Wang

Multiple scattering, modified fragmentation functions and radiative energy loss of a heavy quark propagating in a nuclear medium are investigated in perturbative QCD. Because of the quark mass dependence of the gluon formation time, the medium size dependence of heavy quark energy loss is found to change from a linear to a quadratic form when the initial ene

A. Fix, H. Arenhoevel

The role of final state interaction in $η$ photoproduction on a deuteron as well as on three-body nuclei is investigated within few-body scattering theory. Deviation of the theory from the available experimental results is briefly discussed.

Gabor Fath, Zbigniew Domanski

Cellular differentiation in a developping organism is studied via a discrete bistable reaction-diffusion model. A system of undifferentiated cells is allowed to receive an inductive signal emenating from its environment. Depending on the form of the nonlinear reaction kinetics, this signal can trigger a series of bifurcations in the system. Differentiation s

G. Bianconi, P. Laureti, Y. -K. Yu, Y. -C. Zhang

Is visitors&#39; attendance a fair indicator of a web site&#39;s quality? Internet sub-domains are usually characterized by power law distributions of visits, thus suggesting a richer-get-richer process. If this is the case, the number of visits is not a relevant measure of quality. If, on the other hand, there are active players, i.e. visitors who can tell