April 2003 arXiv papers — page 13

M. Revnivtsev

Results of analysis of RXTE observations of strongly absorbed X-ray sources IGR J16318-4848 and IGR J16358-4726 are presented. Careful subtraction of Galactic ridge emission contribution to the observed spectra of RXTE/PCA allowed us to obtain the spectra of the sources in 3-25 keV energy band. Spectra of the sources cold be well described by a power law wit

A. Kinkhabwala, E. Behar, M. Sako, M. F. Gu

We present a detailed model of the discrete X-ray spectroscopic features expected from steady-state, low-density photoionized plasmas. We apply the Flexible Atomic Code (FAC) to calculate all of the necessary atomic data for the full range of ions relevant for the X-ray regime. These calculations have been incorporated into a simple model of a cone of ions i

I. Mineyev, N. Monod, Y. Shalom

For every hyperbolic group and more general hyperbolic graphs, we construct an equivariant ideal bicombing: this is a homological analogue of the geodesic flow on negatively curved manifolds. We then construct a cohomological invariant which implies that several Measure Equivalence and Orbit Equivalence rigidity results established by Monod-Shalom hold for a

M. Revnivtsev

We present an analysis of the Galactic bulge emission observed by the RXTE/PCA during a set of scans over the Galactic Center field, performed in 1999-2001. The total exposure time of these observations is close to 700 ksec. We construct the distribution of Galactic ridge emission intensity and spectral parameters up to Galactic latitudes b=-10deg;+9deg. We

Piotr Sniady

We study the asymptotic behavior of the free cumulants (in the sense of free probability theory of Voiculescu) of Jucys--Murphy elements--or equivalently--of the transition measure associated with a Young diagram. We express these cumulants in terms of normalized characters of the appropriate representation of the symmetric group S_q. Our analysis considers

Takehiko Yasuda

This paper has been withdrawn by the author due to a crucial error.

Ol'ga V. Dimitrova, M. V. Feigel'man

Detailed theory of phase diagram of clean 2D surface superconductor in a parallel magnetic field is presented. Regular spin-orbital interaction of the Rashba type is known to produce inhomogeneous superconductive state similar to the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) state with $Δ({\bf r})\propto \cos({\bf Qr})$ at high magnetic fields, with $Q \sim gμ_

A. C. Manoharan

Because the subject of relativistic quantum field theory (QFT) contains all of non-relativistic quantum mechanics, we expect quantum field computation to contain (non-relativistic) quantum computation. Although we do not yet have a quantum theory of the gravitational field, and are far from a practical implementation of a quantum field computer, some pieces

L. G. Mardoyan, L. S. Petrosyan, H. A. Sarkisyan

The spherical wave functions of charge-dyon bounded system in a rectangular spherical quantum dot of infinitely and finite height are calculated. The transcendent equations, defining the energy spectra of the systems are obtained. The dependence of the energy levels from the wall sizes is found.

Hayato Goto, Yasuo Yanagihara, Haibo Wang, Tomoyuki Horikiri

An oscillatory correlation function has been observed by the coincidence counting of multimode two-photon pairs produced with a degenerate optical parametric oscillator far below threshold. The coherent superposition of the multimode two-photon pairs provides the oscillation in the intensity correlation function. The experimental data are well fitted to a th

S. E. Emelin

The non-stationary mode of radial-slotted erosive discharge was considered. The existence condition of the relatively steady multiarc regime has been found. Experimentally it has been shown that this discharge has been corresponding to the required condition at the sufficiently large current. The oscillograms of commutation of lightning impulse on the simula

A. C. Ilarraza-Lomelí, R. P. Martínez-y-Romero, H. N. Núñez-Yépez, A. L. Salas-Brito

Recursion formulae are derived for the calculation of two centre matrix elements of a radial function in relativistic quantum mechanics. The recursions are obtained between not necessarily diagonal radial eigensates using arbitrary radial potentials and any radial functions. The only restriction is that the potentials have to share a common minimum. Among ot

Mario Rabinowitz

Electric power is a vital ingredient of modern society. This article is written to provide an insight into the physics and engineering that go into the transmission of electric power and its potential modernization. Topics covered will be Transmission and Distribution, Comparing Overhead and Underground Delivery, Pros and Cons of Underground Delivery, Superc

Irina Yehorchenko

New concept of conditional differential invariant is discussed that would allow description of equations invariant with respect to an operator under a certain condition. Example of conditional invariants of the projective operator is presented.

Leonardo Macarini

We give examples of compact symplectic manifolds with disconnected contact type boundary in dimension $4n$ for any $n\geq 1$. The example is given by a subset of the tangent bundle of a compact quotient of the complex hyperbolic space endowed with the canonical symplectic form plus a generalized magnetic field and its boundary is given by two hypersurfaces o

Florian Luca, Pantelimon Stanica

In this paper we prove two results. The first theorem uses a paper of Kim \cite{K} to show that for fixed primes $p_1,...,p_k$, and for fixed integers $m_1,...,m_k$, with $p_i\not|m_i$, the numbers $(e_{p_1}(n),...,e_{p_k}(n))$ are uniformly distributed modulo $(m_1,...,m_k)$, where $e_p(n)$ is the order of the prime $p$ in the factorization of $n!$. That im

Martin Scharlemann, Jennifer Schultens

We consider compact 3-manifolds M having a submersion h to R in which each generic point inverse is a planar surface. The standard height function on a submanifold of the 3-sphere is a motivating example. To (M, h) we associate a connectivity graph G. For M in the 3-sphere, G is a tree if and only if there is a Fox reimbedding of M which carries horizontal c

Yoonweon Lee

The gluing formula of the zeta-determinant of a Laplacian given by Burghelea, Friedlander and Kappeler contains an unknown constant. In this paper we compute this constant to complete the formula under the assumption of the product structure near boundary. As applications of this result,we prove the adiabatic decomposition theorems of the zeta-determinant of

Hélène Esnault

The eigenvalues of Frobenius acting on $\ell$-adic cohomology of a complete intersection over a finite field have the divisibility predicted by the theorem of Ax and Katz. We have corrected some unforgivable typos.

Paul Langacker

The structure of the standard model is concisely summarized, including the standard model Lagrangian, spontaneous symmetry breaking, the reexpression of the Lagrangian in terms of mass eigenstates after symmetry breaking, and the gauge interactions. The problems of the standard model are described.

K. A. Bronnikov, H. Dehnen, V. N. Melnikov

We use the general solution to the trace of the 4-dimensional Einstein equations for static, spherically symmetric configurations as a basis for finding a general class of black hole (BH) metrics, containing one arbitrary function $g_{tt} = A(r)$ which vanishes at some $r = r_h > 0$, the horizon radius. Under certain reasonable restrictions, BH metrics are f

Burin Gumjudpai, Roy Maartens, Christopher Gordon

We investigate the effects on cosmological density perturbations of dark radiation in a Randall-Sundrum 2 type brane-world. Dark radiation in the background is limited by observational constraints to be a small fraction of the radiation energy density, but it has an interesting qualitative effect in the radiation era. On large scales, it serves to slightly s

Irit Dinur, Venkatesan Guruswami, Subhash Khot, Oded Regev

Given a $k$-uniform hyper-graph, the E$k$-Vertex-Cover problem is to find the smallest subset of vertices that intersects every hyper-edge. We present a new multilayered PCP construction that extends the Raz verifier. This enables us to prove that E$k$-Vertex-Cover is NP-hard to approximate within factor $(k-1-ε)$ for any $k \geq 3$ and any $ε>0$. The result

I. S. Beloborodov, K. B. Efetov, A. V. Lopatin, V. M. Vinokur

We investigate transport in a granular metallic system at large tunneling conductance between the grains, $g_T\gg 1$. We show that at low temperatures, $T\leq g_Tδ$, where $δ$ is the single mean energy level spacing in a grain, the coherent electron motion at large distances dominates the physics, contrary to the high temperature ($T>g_Tδ$) behavior where co

A. N. Rubtsov, T. Janssen

The consequences of the opening of a phason gap in incommensurate systems are studied on a simple model, the discrete frustrated $ϕ^4$-model. Analytical considerations and numerical results show that there is a very weak phase transition that can be characterized as third order.

J. Leonard, M. Walhout, A. P. Mosk, T. Mueller

We produce giant helium dimers by photoassociation of metastable helium atoms in a magnetically trapped, ultracold cloud. The photoassociation laser is detuned red of the atomic $2^3S_1 - 2^3P_0 $ line and produces strong heating of the sample when resonant with molecular bound states. The temperature of the cloud serves as an indicator of the molecular spec

D. V. Spirin

In the paper we describe the modification of spin-wave theory for one-dimensional isotropic antiferromagnet. This theory enables to obtain the energy of magnetic excitations of short wave length and correlation function in agreement with numerical studies.

Joonghoe Dho, N. H. Hur

We have investigated the magnetic and transport properties of Pr$_{0.65}$Ca$_{0.35}$MnO$_3$ and Pr$_{0.82}$Na$_{0.18}$MnO$_3$ with almost same doping level under various magnetic fields. Upon applying a field of 4 T, both compounds undergo a metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM) in the low temperature region. The field-in

Tamas Fulop, Zeno Farkas, Alfred Seeger, Janos Major

We study the inner structure of a positronium confined to a void by treating it as a two-particle quantum system where the electron is captured by an infinite potential well and the positron feels only the Coulomb attraction of the electron. We calculate the ground state and the related quantities that govern the annihilation rate, and discuss implications o

M. O. Katanaev

We consider a wedge dislocation in the framework of elasticity theory and the geometric theory of defects. We show that the geometric theory reproduces quantitatively all the results of elasticity theory in the linear approximation. The coincidence is achieved by introducing a postulate that the vielbein satisfying the Einstein equations must also satisfy th

C. Allende Prieto, T. C. Beers, Y. Li, H. J. Newberg

The Sloan Digital Sky Survey (SDSS) is collecting photometry and intermediate resolution spectra for ~ 10**5 stars in the thick-disk and stellar halo of the Milky Way. This massive dataset can be used to infer the properties of the stars that make up these structures, and considerably deepen our vision of the old components of the Galaxy. We devise tools for

Martin Cohen, Wm. A. Wheaton, S. T. Megeath

Element-by-element we have combined the optical components in the three 2MASS cameras, and incorporated detector quantum efficiency curves and site-specific atmospheric transmissions, to create three relative spectral response curves (RSRs). We provide absolute 2MASS attributes associated with "zero magnitude" in the JHKs bands so that these RSRs may

Omer Blaes, Aristotle Socrates

We examine the local conditions for radiative damping and driving of short wavelength, propagating hydrodynamic and magnetohydrodynamic (MHD) waves in static, optically thick, stratified equilibria. We show that so-called strange modes in stellar oscillation theory and magnetic photon bubbles are intimately related and are both fundamentally driven by the ba

Amjad Hussain Shah Gilani, Riazuddin, T. A. Al-Aithan

The exclusive FCNC beauty semileptonic decay B-> ρis studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.

H. Makino, S. Tasaki

By extending the Berry--Robnik approach for the nearly integrable quantum systems,\cite{[1]} we propose one possible scenario of the energy level spacing distribution that deviates from the Berry--Robnik distribution. The result described in this paper implies that deviations from the Berry--Robnik distribution would arise when energy level components show s

A. A. Malykh, Y. Nutku, M. B. Sheftel

Explicit Riemannian metrics with Euclidean signature and anti-self dual curvature that do not admit any Killing vectors are presented. The metric and the Riemann curvature scalars are homogenous functions of degree zero in a single real potential and its derivatives. The solution for the potential is a sum of exponential functions which suggests that for the

M. Ya. Amusia, V. R. Shaginyan

We consider the behavior of strongly correlated electron liquid in high-temperature superconductors within the framework of the fermion condensation model. We show that at low temperatures the normal state recovered by the application of a magnetic field larger than the critical field can be viewed as the Landau Fermi liquid induced by the magnetic field. In

Ping Huai, Yukihiro Shimoi, Shuji Abe

Intramolecular spin alignment in pi-conjugated molecules is studied theoretically in a model of a Peierls-Hubbard chain coupled with two localized spins. By means of the exact diagonalization technique, we demonstrate that a spin singlet (S=0) to quartet (S=3/2) transition can be induced by electronic doping, depending on the chain length, the positions of t

D. N. Poenaru, W. Greiner

A very general saddle point nuclear shape may be found as a solution of an integro-differential equation without giving apriori any shape parametrization. By introducing phenomenological shell corrections one obtains minima of deformation energy for binary fission of parent nuclei at a finite (non-zero) mass asymmetry. Results are presented for reflection as

F. Bezrukov, D. Levkov, C. Rebbi, V. Rubakov

We make use of a semiclassical method for calculating the suppression exponent for topology changing transitions in high-energy electroweak collisions. In the Standard Model these processes are accompanied by violation of baryon and lepton number. By using a suitable computational technique we obtain results for s-wave scattering in a large region of initial

Jing-Min Hou, Mo-Lin Ge

The Bose-Hubbard Hamiltonian of spin-2 cold bosons with repulsive interaction in an optical lattice is proposed. After neglecting the hopping term, the site-independent Hamiltonian and its energy eigenvalues and eigenstates are obtained. We consider the hopping term as a perturbation to do the calculations in second order and draw the phase diagrams for diff

Masako Fujita, Hiroyuki Hata

We study time dependent solutions in cubic open string field theory which are expected to describe the configuration of the rolling tachyon. We consider the truncated system consisting of component fields of level zero and two, which are expanded in terms of cosh n x^0 modes. For studying the large time behavior of the solution we need to know the coefficien

J. N. Das, K. Chakrabarti, S. Paul

In this article we present triple differential cross sections for equal energy sharing kinematics for double photoionization of the helium atom at 20 and 40eV above threshold in the framework of the hyperspherical partial wave theory. This supplements our earlier work \cite{DCP03} in which we were successful in showing fully, gauge independence of the result

Hjalmar Rosengren, Michael Schlosser

Using multiple q-integrals and a determinant evaluation, we establish a multivariable extension of Bailey's nonterminating 10-phi-9 transformation. From this result, we deduce new multivariable terminating 10-phi-9 transformations, 8-phi-7 summations and other identities. We also use similar methods to derive new multivariable 1-psi-1 summations. Some of

H. Belich, J. L. Boldo, L. P. Colatto, J. A. Helayel-Neto

Focusing on gauge degrees of freedom specified by a 1+3 dimensions model hosting a Maxwell term plus a Lorentz and CPT non-invariant Chern-Simons-like contribution, we obtain a minimal extension of such a system to a supersymmetric environment. We comment on resulting peculiar self-couplings for the gauge sector, as well as on background contribution for gau

Chiara Macchiavello

We study the issue of simultaneous estimation of several phase shifts induced by commuting operators on a quantum state. We derive the optimal positive operator-valued measure corresponding to the multiple-phase estimation. In particular, we discuss the explicit case of the optimal detection of double phase for a system of identical qutrits and generalise th

Jeroen Dehaene, Bart De Moor

We describe stabilizer states and Clifford group operations using linear operations and quadratic forms over binary vector spaces. We show how the n-qubit Clifford group is isomorphic to a group with an operation that is defined in terms of a (2n+1)x(2n+1) binary matrix product and binary quadratic forms. As an application we give two schemes to efficiently

Yoshiyuki Tsuda, Keiji Matsumoto, Masahito Hayashi

For the quantum Gaussian state family, Hayashi proposed a quantum mechanical operation using beam splitters to estimate the location and scale parameters of the P-function, and he showed that it is asymptotically optimal. In this paper, we analyze the effect of disturbance of his operation caused by the randomness of the transparency of the beam splitters. I

Carolina Moura Alves, Pawel Horodecki, Daniel K. L. Oi, L. C. Kwek

We present a method of determining important properties of a shared bipartite quantum state, within the ``distant labs'' paradigm, using \emph{only} local operations and classical communication (LOCC). We apply this procedure to spectrum estimation of shared states, and locally implementable structural physical approximations to incompletely positive

Z. Jane Wang

Unlike a helicopter, an insect can, in theory, use both lift and drag to stay aloft. Here we show that a dragonfly uses mostly drag to hover by employing asymmetric up and down strokes. Computations of a family of strokes further show that using drag can be as efficient as using lift at the low Reynolds number regime appropriate for insects.

W. J. Mullin, G. Blaylock

Physicists often claim that there is an effective repulsion between fermions, implied by the Pauli principle, and a corresponding effective attraction between bosons. We examine the origins of such exchange force ideas, the validity for them, and the areas where they are highly misleading. We propose that future explanations of quantum statistics should avoi

B. B. Blinov

Frequent polarization reversals, or spin-flips, of a stored polarized beam in a high energy scattering asymmetry experiments may greatly reduce systematic errors of spin asymmetry measurements. A spin-flipping technique is being developed by using rf magnets running at a frequency close to the spin precession frequency, thereby creating spin-depolarizing res

K. D. Sviratcheva, C. Bahri, A. I. Georgieva, J. P. Draayer

The quantum deformation concept is applied to a study of isovector pairing correlations in nuclei of the mass 40<A<100 region. While the non-deformed (q -> 1) limit of the theory provides a reasonable global estimate for strength parameters of the pairing interaction, the results show that the q-deformation plays a significant role in understanding higher-or

R. Lednicky

The influence of the multi-boson effects on pion multiplicities, single-pion spectra and two-pion correlation functions is discussed in terms of an analytically solvable model. It is argued that spectacular multi-boson effects are likely to be observed only in the rare events containing sufficiently high density fluctuations. The possibilities of unlike part

R. Lednicky

The possibilities of unlike particle correlations for a study of the space-time asymmetries in particle production, including the sequence of particle emission, are demonstrated.

R. Lednicky, S. Panitkin, N. Xu

The possibilities of unlike particle correlations for a study of particle delays and spatial shifts in relativistic heavy ion collisions are demonstrated. This report represents the unpublished Ref. [4] in the paper by S. Voloshin et al., Phys. Rev. Lett. {\bf 79} (1977) 4766; the report abstract was submitted to the conference Quark Matter&#39;97.

Brandon P. van Zyl, D. A. W. Hutchinson

Using two distinct inversion techniques, the local one-dimensional potentials for the Riemann zeros and prime number sequence are reconstructed. We establish that both inversion techniques, when applied to the same set of levels, lead to the same fractal potential. This provides numerical evidence that the potential obtained by inversion of a set of energy l

R. Skip Garibaldi

Let BG be a classifying variety for an exceptional simple simply connected algebraic group G. We compute the degree 3 unramified Galois cohomology of BG with values in Q/Z(2) over an arbitrary field F. Combined with a paper by Merkurjev, this completes the computation of these cohomology groups for G semisimple simply connected over all fields. These computa

Weiping Zhang

In this talk, we review the heat kernel approach to the Atiyah-Singer index theorem for Dirac operators on closed manifolds, as well as the Atiyah-Patodi-Singer index theorem for Dirac operators on manifolds with boundary. We also discuss the odd dimensional counterparts of the above results. In particular, we describe a joint result with Xianzhe Dai on an i

Richard Evan Schwartz

The theory of complex hyperbolic discrete groups is still in its childhood but promises to grow into a rich subfield of geometry. In this paper I will discuss some recent progress that has been made on complex hyperbolic deformations of the modular group and, more generally, triangle groups. These are some of the simplest nontrivial complex hyperbolic discre

Xiaochun Rong

In the last two decades, one of the most important developments in Riemannian geometry is the collapsing theory of Cheeger-Fukaya-Gromov. A Riemannian manifold is called (sufficiently) collapsed if its dimension looks smaller than its actual dimension while its sectional curvature remains bounded (say a very thin flat torus looks like a circle in a bared eye

Anton Petrunin

In my talk I will discuss the following results which were obtained in joint work with Wilderich Tuschmann. 1. For any given numbers $m$, $C$ and $D$, the class of $m$-dimensional simply connected closed smooth manifolds with finite second homotopy groups which admit a Riemannian metric with sectional curvature $\vert K \vert\le C$ and diameter $\le D$ conta

Yiming Long

In recent years, we have established the iteration theory of the index for symplectic matrix paths and applied it to periodic solution problems of nonlinear Hamiltonian systems. This paper is a survey on these results.

Peter Li

In this talk, I will discuss the use of harmonic functions to study the geometry and topology of complete manifolds. In my previous joint work with Luen-fai Tam, we discovered that the number of infinities of a complete manifold can be estimated by the dimension of a certain space of harmonic functions. Applying this to a complete manifold whose Ricci curvat

Weiyue Ding

We present some recent results on the existence of solutions of the Schrödinger flows, and pose some problems for further research.

Xiuxiong Chen

In recent years, there are many progress made in Kähler geometry. In particular, the topics related to the problems of the existence and uniqueness of extremal Kähler metrics, as well as obstructions to the existence of such metrics in general Kähler manifold. In this talk, we will report some recent developments in this direction. In particular, we will dis

Hubert L. Bray

In a paper \cite{P} in 1973, R. Penrose made a physical argument that the total mass of a spacetime which contains black holes with event horizons of total area $A$ should be at least $\sqrt{A/16π}$. An important special case of this physical statement translates into a very beautiful mathematical inequality in Riemannian geometry known as the Riemannian Pen

Paul Biran

In this paper we survey several intersection and non-intersection phenomena appearing in the realm of symplectic topology. We discuss their implications and finally outline some new relations of the subject to algebraic geometry.

Robert Bartnik

Physicists believe, with some justification, that there should be a correspondence between familiar properties of Newtonian gravity and properties of solutions of the Einstein equations. The Positive Mass Theorem (PMT), first proved over twenty years ago \cite{SchoenYau79b,Witten81}, is a remarkable testament to this faith. However, fundamental mathematical

I. Dolgachev

An abstract $(v_k,b_r)$-configuration is a pair of finite sets of cardinalities $v$ and $b$ with a relation on the product of the sets such that each element of the first set is related to the same number $k$ of elements from the second set and each element of the second set is related to the same number $r$ of elements in the first set. An example of an abs

Ben Andrews

In this talk I will discuss an example of the use of fully nonlinear parabolic flows to prove geometric results. I will emphasise the fact that there is a wide variety of geometric parabolic equations to choose from, and to get the best results it can be very important to choose the best flow. I will illustrate this in the setting of surfaces in a three-dime

Andrew R. Teel, Antonio Loria, Elena Panteley, Dobrivoje Popovic

We present a new result on uniform attractivity of the origin for nonlinear time-varying systems. Our theorem generalizes Matrosov&#39;s theorem which extends, in a certain manner, Krasovskii-LaSalle invariance principle to the case of general nonlinear time-varying systems. We show the utility of our theorem by addressing a control problem of port interconn

N. Crampe&#39;

The Yangian of the Lie algebra sl_n is known to have different presentations, in particular the RTT realisation and the Drinfel&#39;d realisation. Using the isomorphism between them, the explicit expressions of the comultiplication, the antipode and the counit in the Drinfel&#39;d realisation of the Yangian Y(sl_n) are given. As examples, the cases of Y(sl_2

Roman Drnovšek

We prove some inequalities for the spectral radius of positive operators on Banach function spaces. In particular, we show the following extension of Levinger&#39;s theorem. Let $K$ be a positive compact kernel operator on $L^2(X,μ)$ with the spectral radius $r(K)$. Then the function $ϕ$ defined by $ϕ(t) = r(t K + (1-t) K^*)$ is non-decreasing on $[0, {1/2}]

Roland Bacher

We associate to certain symmetric or antisymmetric functions on the set ${E\choose d+1}$ of $(d+1)-$subsets in a finite set $E$ an equivalence relation on $E$ and study some of its properties.

Dimitri Zvonkine

The Hurwitz space is a compactification of the space of rational functions of a given degree. We study the intersection of various strata of this space with its boundary. A study of the cohomology ring of the Hurwitz space then allows us to obtain recurrence relations for certain numbers of ramified coverings of a sphere by a sphere with prescribed ramificat

Vladimir Dergachev

We study pairs of associative algebras and linear functionals. New results together with corrected proofs for previously published material are presented. In particular, we prove the identity ind Mat(n) (#) A=n * ind A$ for finite-dimensional unital associative algebra A with index 1. [ Symbol (#) denotes tensor product ]

A. P. Baeta Scarpelli, M. Botta Cantcheff, J. A. Helayel-Neto

In this paper, we show that the propagator of the dual of a general Proca-like theory, derived from the gauging iterative Noether Dualization Method, can be written by means of a simple relation between known propagators. This result is also a demonstration that the Lagrangian obtained by dualization describes the same physical particles as the ones present

A. V. Lipatov, N. P. Zotov

We calculate the cross section and the transverse momentum distribution of inclusive J/ψproduction in γγcollisions at CERN LEP2 within the colour singlet model and the k_T-factorization approach, including both direct and resolved photon contributions. The unintegrated gluon distribution in the photon is determined, using the Blumlein&#39;s prescription for

Fran De Aquino

A experimental test based on the inverse Compton effect (photon-electron collision) is proposed to check the Kinetic Quantum Gravity Theory. The experimental set-up point out a possible propulsionsystem, based on gravity control.

Joseph O&#39;Rourke

The open problem of whether or not every pair of equal-area polygons has a hinged dissection is discussed.

T. J. Sato, S. -H. Lee, T. Katsufuji, M. Masaki

We used inelastic neutron scattering to show that well below its Néel temperature, $T_{\rm N}$, the two-dimensional (2D) XY nearly-triangular antiferromagnet YMnO$_{3}$ has a prominent {\it central peak} associated with 2D antiferromagnetic fluctuations with a characteristic life time of 0.55(5) ps, coexisting with the conventional long-lived spin-waves. Exi

Gerrit E. W. Bauer, Yaroslav Tserkovnyak, Daniel Huertas-Hernando, Arne Brataas

Magnetoelectronics is mainly digital, i.e. governed by up and down magnetizations. In contrast, analogue magnetoelectronics makes use of phenomena occuring for non-collinear magnetization configurations. Here we review theories which have recently been applied to the transport in non-collinear magnetic nanostructures in two and multiterminal structures, viz.

Alessandro Cuccoli, Tommaso Roscilde, Ruggero Vaia, Paola Verrucchi

We consider the Heisenberg antiferromagnet on the square lattice with S=1/2 and very weak easy-plane exchange anisotropy; by means of the quantum Monte Carlo method, based on the continuous-time loop algorithm, we find that the thermodynamics of the model is highly sensitive to the presence of tiny anisotropies and is characterized by a crossover between iso

P. Jiji Thomas Joseph, Prabhakar P. Singh

Using the Korringa-Kohn-Rostoker coherent-potential approximation in the atomic-sphere approximation (KKR-ASA CPA) we have studied the changes in the electronic structure and the superconducting transition temperature T_{c} in Nb_{1-x}B_{2} alloys as a function of x. We find that the variation in the electronic structure of Nb_{1-x}B_{2} alloys as a function

Prabhakar P. Singh

We have studied the changes in the electronic structure and the superconducting transition temperature T_c of Mg(B_{1-x}C_{x})_{2} alloys as a function of x with 0\leq x\leq 0.3. Our density-functional-based approach uses coherent-potential approximation to describe the effects of disorder, Gaspari-Gyorffy formalism to estimate the electron-phonon matrix ele

A. Carrington, P. J. Meeson, J. R. Cooper, L. Balicas

We report measurements of the de Haas-van Alphen effect for single crystals of MgB$_2$, in magnetic fields up to 32 Tesla. In contrast to our earlier work, dHvA orbits from all four sheets of the Fermi surface were detected. Our results are in good overall agreement with calculations of the electronic structure and the electron-phonon mass enhancements of th

Jean-Pierre Eckmann, Elisha Moses, Danilo Sergi

Connectivity and topology are known to yield information about networks, whose origin is self-organized, but the impact of {\it temporal dynamics} in a network is still mostly unexplored. Using an information theoretic approach to e-mail exchange, we show that an e-mail network allows for a separation of static and dynamic structures within it. The static st

H. H. Wensink, G. J. Vroege

The isotropic-nematic phase behavior of length polydisperse hard rods with arbitrary length distributions is calculated. Within a numerical treatment of the polydisperse Onsager model using the Gaussian trial function Ansatz we determine the onset of isotropic-nematic phase separation, coming from a dilute isotropic phase and a dense nematic phase. We focus

A. Trovato, F. Seno

For many years it had been believed that steric compatibility of helix interfaces could be the source of the observed preference for particular angles between neighbouring helices as emerging from statistical analysis of protein databanks. Several elegant models describing how side chains on helices can interdigitate without steric clashes were able to accou

A. Cehovin, C. M. Canali, A. H. MacDonald

We present a theory of the elementary spin excitations in transition metal ferromagnet nanoparticles which achieves a unified and consistent quantum description of both collective and quasiparticle physics. The theory starts by recognizing the essential role played by spin-orbit interactions in determining the energies of ferromagnetic resonances in the coll

Amit Dutta, Diptiman Sen

We study the anisotropic Heisenberg (XYZ) spin-1/2 chain placed in a magnetic field pointing along the x-axis. We use bosonization and a renormalization group analysis to show that the model has a non-trivial fixed point at a certain value of the XY anisotropy a and the magnetic field h. Hence, there is a line of critical points in the (a,h) plane on which t

A. A. Cherechukin, V. V. Khovailo, R. V. Koposov, E. P. Krasnoperov

The temperature and magnetic field dependencies of Ni-Mn-Ga polycrystals deformation are investigated. Ingots were prepared by arc-melting in argon atmosphere and further annealing. A training procedure (cycling across the martensitic transition point) for the two-way shape-memory effect was performed with Ni$_{2.16}$Fe$_{0.04}$Mn$_{0.80}$Ga samples. Changes

V. K. Henner, I. V. Kaganov

Phenomenological theory of superradiation from crystals of high-spin molecules is suggested. We show that radiation friction can cause a superradiation pulse and investigate the role of magnetic anisotropy, external magnetic field and dipole-dipole interactions. Depending on the contribution of all these factors at low temperature, several regimes of magneti

A. Bianchi, R. Movshovich, C. Capan, A. Lacerda

We report specific heat measurements of the heavy fermion superconductor CeCoIn5 in the vicinity of the superconducting critical field H_{c2}, with magnetic field in the [110], [100], and [001] directions, and at temperatures down to 50 mK. The superconducting phase transition changes from second to first order for field above 10 T for H || [110] and H || [1

Sung- Sik Lee, Sung-Ho Suck Salk

To supplement our recent brief report on the theory of holon-pair boson approach to the t-J Hamiltonian [S.-S. Lee and Sung-Ho Suck Salk, Phys. Rev. B {\bf 64}, 052501(2001)], in this paper we present a full exposure to the theory, detailed physical implications and predicted various physical properties of high $T_c$ cuprates. We discuss the significance of

Martin Cohen, S. T. Megeath, Peter L. Hammersley, Fabiola Martin-Luis

We describe the technique used to develop on-orbit calibrators for IRAC and validate the method for either K0-M0III or A0-A5V stars. For SIRTF, the approach uses all available optical, NIR, and MIR photometry, and yields absolute spectra from UV to MIR. One set of stars is from Landolt&#39;s network of optical standards, the other from Carter-Meadows IR stan

Vadim A. Arefiev, William C. Priedhorsky, Konstantin N. Borozdin

Fast X-ray transients (FXTs) with timescales from seconds to hours have been seen by numerous space instruments. We have assembled archival data from Ariel-5, HEAO-1 (A-1 and A-2), WATCH, ROSAT, and Einstein to produce a global fluence-frequency relationship for these events. Fitting the log N-log S distribution over several orders of magnitude to simple pow

E. Berger

Radio observations of gamma-ray burst (GRB) afterglows provide both complementary and unique diagnostics of the afterglow physics and environment of the burst. Here we concentrate on three unique aspects of GRB energetics and environments afforded by radio and submillimeter observations: the non-relativistic evolution of the fireball, the density profile of

W. Kluzniak, M. Abramowicz

Millisecond variability detected in low-mass X-ray binaries (LMXBs) probably reflects motions of accreting fluid in the strong-field gravity of neutron stars or neutron stars. Parametric resonance between two oscillators with unequal eigenfrequencies provides a natural explanation for the 2:3 frequency ratio observed in some black-hole systems, and probably