September 2001 arXiv papers — page 7

Paolo Piccione, Daniel V. Tausk

We consider solutions of Lagrangian variational problems with linear constraints on the derivative. These solutions are given by curves $γ$ in a differentiable manifold $M$ that are everywhere tangent to a smooth distribution $\mathcal D$ on $M$; such curves are called horizontal. We study the manifold structure of the set $Ω_{P,Q}(M,\mathcal D)$ of horizont

George Siopsis, Suphot Musiri

We discuss the quantization of a self-interacting string consisting of maximally charged matter. We construct the Hamiltonian in the non-relativistic limit by expanding around a static solution of the Einstein-Maxwell field equations. Conformal symmetry is broken on the worldsheet, but a subgroup of the conformal group acts as the gauge group of the theory.

Collin Bennett, Thomas Branson

We compute the number of linearly independent ways in which a tensor of Weyl type may act upon a given irreducible tensor-spinor bundle V over a Riemannian manifold. Together with the analogous but easier problem involving actions of tensors of Einstein type, this enumerates the possible curvature actions on V.

Beatriz Gato-Rivera

We write down one-to-one mappings between the singular vectors of the Neveu-Schwarz N=2 superconformal algebra and $16 + 16$ types of singular vectors of the Topological and of the Ramond N=2 superconformal algebras. As a result one obtains construction formulae for the latter using the construction formulae for the Neveu-Schwarz singular vectors due to Dörr

Pieter-Jan De Smet

In this Ph.D. thesis, we study tachyon condensation in string field theories. In chapter 2, we review Witten's bosonic string field theory and calculate the tachyon potential. In chapter 3, we calculate the tachyon potential in Berkovits' superstring field theory. In chapter 4, we look for exact solutions in a toy model. Unpublished result: we use co

Ivan Avramidi, Thomas Branson

We initiate a systematic study of natural differential operators in Riemannian geometry whose leading symbols are not of Laplace type. In particular, we define a discrete leading symbol for such operators which may be computed pointwise, or from spectral asymptotics. We indicate how this can be applied to the computation of another kind of spectral asymptoti

I. Hinchliffe, N. Kersting

This brief Letter demonstrates that effects from a $\nc$ space-time geometry will measurably affect the value of $(g-2)_μ$ inferred from the decay of the muon to an electron plus two neutrinos. If the scale of noncommutivity is ${\cal O}(TeV)$, the alteration of the $V-A$ structure of the lepton-lepton-W vertex is sufficient to shift the inferred value of $(

A. Kurylov, M. J. Ramsey-Musolf

We compute the complete one-loop contributions to low-energy charged current weak interaction observables in the Minimal Supersymmetric Standard Model (MSSM). We obtain the constraints on the MSSM parameter space which arise when precision low-energy charged current data are analyzed in tandem with measurements of the muon anomaly. While the data allow the p

Daniel Boer

Theoretical aspects of transversity observables are reviewed. The main focus is on two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions. Electron-positron annihilation experiments which are required to obtain these fragmentation functions are discussed, as well as th

Mrinal Dasgupta

This article provides a review of progress made in understanding inverse power law corrections 1/Q^p where Q is the hard scale for a given QCD observable. Special emphasis is given to comparisons of theory with HERA results.

Stefano Forte

We review the physics potential for experiments with intense neutrino beams at the front-end of a muon storage ring, stressing the way the spin and flavour structure of neutrino interactions with matter can be used to shed light on the structure of the strong and electroweak interactions. Specifically, we discuss precision tests of the standard model, studie

J. Aysto, A. Baldini, A. Blondel, A. de Gouvea

The physics potential of an intense source of low-energy muons is studied. Such a source is a necessary stage towards building the neutrino factories and muon colliders which are being considered at present. The CERN Neutrino Factory could deliver muon beams with intensities 3-4 orders of magnitude higher than available now, with large freedom in the choice

M. Consoli

We illustrate why a space-time structure as in General Relativity is not in contradiction with a dynamical origin of gravity from a scalar field. Further, we argue that the recently discovered gap-less mode of the singlet Higgs field represents the most natural dynamical agent of Newtonian gravity.

Wojciech Krolikowski

An effective texture is presented for six Majorana conventional neutrinos (three active and three sterile), based on a 6x6 neutrino mixing matrix whose 3x3 active-active component arises from the popular bimaximal mixing matrix of active neutrinos $ν_e$, $ν_μ$, $ν_τ$ by three small rotations in the 14, 25, 36 planes of $ν_1$, $ν_2$, $ν_3$ and $ν_4$, $ν_5$, $

A. K. Chaudhuri

We have studied possible formation of $Θ$ vacua states in heavy ion collisions. Random phases of the chiral fields were evolved in a finite temperature potential, incorporating the breaking of $U_A(1)$ symmetry. Initial random phases very quickly settle into oscillation around the values dictated by the potential. The simulation study indicate that an initia

Jianwei Qiu, Xiaofei Zhang

We calculate nuclear effect in Drell-Yan massive lepton-pair production in terms of parton multiple scattering in Quantum Chromodynamics (QCD). We present the nuclear modification to inclusive Drell-Yan cross section $dσ/dQ^2$ in terms of multiparton correlation functions. By extracting the size of the correlation functions from measured Drell-Yan transverse

Prashanth Jaikumar, Ismail Zahed

We formulate a toy model for the $θ$ vacuum that embodies the n-point moments of the even and odd topological charge densities. The partition function is $2π$ periodic only after resumming over all winding modes. We apply the same analysis to the quenched instanton vacuum at finite $θ$ and derive saddle-point results for the vacuum energy density that are ma

Felix Sefkow

We review measurements of open beauty production at HERA, with emphasis on recent results based on lifetime signatures. The beauty cross sections in photoproduction and deep-inelastic scattering are found to be higher than expected in QCD at next-to-leading order. The discussion includes new results on beauty production in e+e-, gamma-gamma and p-bar-p inter

L3 Collaboration

The reactions ee->ee+pi0+X and ee->ee+K0s+X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum pt and the pseudo-rapidity. For pt < 1.5 GeV, the pi0 and K0s differential cross sections are describe

L3 Collaboration

Bose-Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in the four-momentum difference range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be smaller than that of charged pions. This result is

Geoffrey Martin

This article investigates an extension of General Relativity based upon a class of lifted metrics on the cotangent bundle of space-time. The dynamics of the theory is determined by a fixed section of the cotangent bundle, representing the momentum of a fluid flow, and Einstein&#39;s equations for the fluid applied to the induced space-time metric on the subm

Winfried Zimdahl, Alexander B. Balakin

Introducing an effective refraction index of an isotropic cosmic medium, we investigate the cosmological fluid dynamics which is consistent with a conformal, timelike symmetry of a corresponding ``optical&#39;&#39; metric. We demonstrate that this kind of symmetry is compatible with the existence of a negative viscous pressure and, consequently, with cosmolo

Robert B. Horwitz

The paper examines the South African transition from apartheid to democracy through the lens of the reform of the communication sector. Through a set of participatory stakeholder consultative processes, the institutions of broadcasting, telecommunications, print press, and state information agency underwent reform in a process I refer to as &#39;negotiated l

Tony Christensen, Peter McCormick

The early election call in the fall of 2000 provided the perfect opportunity to study the impact the Internet has had on election campaigning in Canada. With the explosion of use the Net has seen since the 1997 general election, Canadian federal parties stood at the threshold of a new age in election campaigning. Pundits such as Rheingold (1993) have argued

Clelia Piragibe

The current pattern of competition in the Brazilian telecommunications market was defined by a regulatory reform implemented in the second half of the nineties. The telecommunications regulatory reform discussed in the paper promoted the privatization of Telebras System and fostered competition in the Brazilian market under the stricted supervision of the ne

Neil Netanel

Is a commercial mass media, dependent on the market for its sustenance, necessary, or even desirable, for liberal democracy? Yochai Benkler has argued that a decentralized, peer-to-peer system of communications and information is both possible with digital technology and preferable to a system based on commercial mass media. He has contended in fact that the

Sharon Strover, Michael Oden, Nobuya Inagaki

This research investigates the relationship between telecommunications infrastructure, economic conditions, and federal and state policies and initiatives. It presents a detailed look at the telecommunications environment of the Appalachian region, particularly focusing on broadband technologies. A strong, positive association exists between telecommunicatio

Peter P. Swire

&#34;What Should be Hidden and Open in Computer Security: Lessons from Deception, the Art of War, Law, and Economic Theory&#34; Peter P. Swire, George Washington University. Imagine a military base. It is defended against possible attack. Do we expect the base to reveal the location of booby traps and other defenses? No. But for many computer applications,a

Sangin Park

In this paper, we aim to empirically examine the value of website usage and sellers&#39; listing behavior in the two leading Internet auctions sites, eBay and Yahoo!Auctions. The descriptive data analysis of the seller&#39;s equilibrium listing behavior indicates that a seller&#39;s higher expected auction revenue from eBay is correlated with a lager number

John B. Horrigan

This paper looks at five U.S. cities (Austin, Cleveland, Nashville, Portland, and Washington, DC) and explores strategies being employed by community activists and local governments to create and sustain community networking projects. In some cities, community networking initiatives are relatively mature, while in others they are in early or intermediate sta

Charles N. Davis

This article addresses the U.S. Supreme Court&#39;s central purpose formulation in Reporters Committee v. Department of Justice under the federal Freedom of Information Act. By examining all lower federal court opinions interpreting Reporters Committee and by analyzing the effects of the Court&#39;s opinion on the implementation of the FOIA, the paper finds

Karen Clay, Michael Smith, Eric Wolff

Low search costs in Internet markets can be used by consumers to find low prices, but can also be used by retailers to monitor competitors&#39; prices. This price monitoring can lead to price matching, resulting in dampened price competition and higher prices in some cases. This paper analyzes price data for 316 bestselling, computer, and random book titles

Martin Dowding

This exploratory and descriptive research compares the policy-making processes and policy recommendations regarding universal service and universal access developed by the U.S. National Information Infrastructure Advisory Council (NIIAC) and the Canadian Information Highway Advisory Council (IHAC) in conjunction with related federal government agencies. Crea

William Yurcik, David Doss

Information technology is redefining national security and the use of force by state and nonstate actors. The use of force over the Internet warrants analysis given recent terrorist attacks. At the same time that information technology empowers states and their commercial enterprises, information technology makes infrastructures supported by computer systems

Murali Venkatesh, Dong-Hee Shin

Drawing on an ongoing longitudinal research study, we discuss problems in the development of five next generation community networking projects in central New York. The projects were funded under a state program to diffuse broadband technologies in economically depressed areas of the state. The networks are technologically complex and entail high costs for s

A. Michael Froomkin, Mark A. Lemley

The Internet Corporation for Assigned Names and Numbers (ICANN) is a private non-profit company which, pursuant to contracts with the US government, acts as the de facto regulator for DNS policy. ICANN decides what TLDs will be made available to users, and which registrars will be permitted to offer those TLDs for sale. In this article we focus on a hitherto

Lucia Piscitello, Francesca Sgobbi

The debate on the Information Society shows large agreement on the assumption that the promised benefits will fully display only if the diffusion of ICTs and the Internet will involve all the actors of the socio-economic system. Accordingly, special emphasis is put on the participation of small and medium enterprises (SMEs), but also on public administration

Alberto Momigliano, Frank Pfenning

We address the problem of complementing higher-order patterns without repetitions of existential variables. Differently from the first-order case, the complement of a pattern cannot, in general, be described by a pattern, or even by a finite set of patterns. We therefore generalize the simply-typed lambda-calculus to include an internal notion of strict func

Martha Garcia-Murillo, Ian MacInnes

Rules are necessary to provide or shape the incentives of individuals and organizations. This is particularly true when free markets lead to undesirable outcomes. The Telecommunications Act of 1996 attempted to create incentives to foster competition. Ambiguity as well as the timing of the Act has led to delays in the clarification of rules and the rapid obs

Phil Weiser

Networks Unplugged: Towards A Model of Compatibility Regulation Between Information Platforms This Article outlines a basic model for regulating interoperability between rival information platforms. In so doing, it insists that antitrust, intellectual property, and telecommunications regulation all must follow the same set of principles to facilitate competi

Nicholas Economides

This paper analyzes the law and economics of United States v. Microsoft, a landmark case of antitrust intervention in network industries. [abridged]

Eszter Hargittai

Much of the existing approach to the digital divide suffers from an important limitation. It is based on a binary classification of Internet use by only considering whether someone is or is not an Internet user. To remedy this shortcoming, this project looks at the differences in people&#39;s level of skill with respect to finding information online. Finding

Martin B. H. Weiss, Hak-Ju Kim

There have been a small number of cost studies of Voice over IP (VoIP) in the academic literature. Generally, they have been for abstract networks, have not been focused on the public switched telephone network, or they have not included the operating costs. This paper presents the operating cost portion of our ongoing research project comparing circuit-swit

Tomasz Szczygiel

The paper presents two CLP approaches to 2D angle placements, implemented in CHIP v.5.3. The first is based on the classical (rectangular) cumulative global constraint, the second on the new trapezoidal cumulative global constraint. Both approaches are applied to a specific presented.

G. Anandalingam

In this paper, we assess the applicability of auctions based on the Vickrey second price model for allocating wireless spectrum in developing countries. We first provide an overview of auction models for allocating resources. We then examine the experience of auctioning spectrum in different countries. Based on this examination, we posit some axioms that see

Laurence J. Malone

This paper explores commonalities between the creation of the Rural Electrification Administration and the similar dilemma of providing an affordable infrastructure for high-speed Internet access in places where profit incentives do not exist. In the case of the R.E.A., the necessity for an aggressive federal initiative to wire rural America, where the marke

Richard Cawley

It has proved to be difficult to translate the lessons from the literature on universal service into the policy framework because of political interests and regulatory capture. Neither the USA or Europe has made a very good job of devising a clean framework and the WTO agreement is sparing in this area. A number of pressures in the European context have enab

Rajni Gupta

After the 1991 economic policy made a shift from a closed economic model to a market-oriented model. The government invited private sector to participate in reforming its telecom sector. However, the government took a half-hearted approach in overhauling the legal and regulatory regime, suitable for competitive regime or in framing the 1994 Telecom Policy. C

Todd Sinai, Joel Waldfogel

By combining persons around the world into a single market, the Internet may serve as a substitute for urban agglomeration. That is, the Internet may level the consumption playing field between large, variety-laden and small, variety-starved markets. However, if local content on the Internet is more prevalent in larger markets, then the Internet may be a com

Antonio J. Fernandez, Patricia M. Hill

This paper focuses on the branching process for solving any constraint satisfaction problem (CSP). A parametrised schema is proposed that (with suitable instantiations of the parameters) can solve CSP&#39;s on both finite and infinite domains. The paper presents a formal specification of the schema and a statement of a number of interesting properties that,

Michelle S. Kosmidis

The Internet is changing rapidly the way people around the world communicate, learn, and work. Yet the tremendous benefits of the Internet are not shared equally by all. One way to close the gap of the &#34;digital divide&#34; is to ensure Internet access to all schools from an early age. While both the USA and EU have embraced the promotion of Internet acce

Neil Gandal, David Salant, Leonard Waverman

The issue of market-based versus mandated standards has been addressed in many settings. In most settings in which network effects are present, compatibility across platforms has been a key determinant of the success or failure of a particular technology. In the case of wireless telecommunications, however, interconnection and the availability of the relevan

Tair-Rong Sheu, Kathleen Carley

E-Commerce challenges traditional approaches to assessing monopolistic practices due to the rapid rate of growth, rapid change in technology, difficulty in assessing market share for information products like web sites, and high degree of interconnectivity and alliance formation among corporations. This paper has provided a fundamental framework that integra

Michael R. Ward, Yu-Ching Chen

Consumers value keeping some information about them private from potential marketers. E-commerce dramatically increases the potential for marketers to accumulate otherwise private information about potential customers. Online marketers claim that this information enables them to better market their products. Policy makers are currently drafting rules to regu

Derrick L. Cogburn

This paper develops a theoretical perspective on globalization and the Information Society and combines it with a critical usage of international regime theory as a heuristic for understanding the current historical period of transition from an international telecommunicaitons regime (Cowhey, 1990; 1994) to a new and complex regime aimed at providing governa

A. P. F. Atman, J. G. Moreira

In a roughening process, the growth exponent $β$ describes how the roughness $w$ grows with the time $t$: $w\sim t^β$. We determine the exponent $β$ of a growth process generated by the spatiotemporal patterns of the one dimensional Domany-Kinzel cellular automaton. The values obtained for $β$ shows a cusp at the frozen/active transition which permits determ

Gemunu H. Gunaratne

Disordered networks of fragile elastic elements have been proposed as a model for inner porous regions of large bones [Gunaratne et.al., cond-mat/0009221]. In numerical studies, weakening of such networks is seen to be accompanied by reductions in the fraction of load carrying bonds. This observation is used to show that the ratio $Γ$ of linear responses of

A. P. F. Atman, Ronald Dickman, J. G. Moreira

The critical behavior at the frozen/active transition in the Domany-Kinzel stochastic cellular automaton (DKCA) is studied {\it via} a surface growth process in (1+1) dimensions. At criticality, this process presents a kinetic roughening transition; we measure the critical exponents in simulations. Two update schemes are considered: in the symmetric scheme,

A. J. Millis, A. J. Schofield, G. G. Lonzarich, S. A. Grigera

A renormalization group treatment of metamagnetic quantum criticality in metals is presented. In clean systems the universality class is found to be of the overdamped, conserving (dynamical exponent z=3) Ising type. Detailed results are obtained for the field and temperature dependence of physical quantities including the differential susceptibility, resisti

Monica Soler, Pau Artus, Kirsten Folting, John C. Huffman

Methods are reported for the preparation of mixed-carboxylate versions of the [Mn12O12(O2CR)16(H2O)4] family of single-molecule magnets (SMMs). [Mn12O12(O2CCHCl2)8(O2CCH2But)8(H2O)3] (5) and [Mn12O12(O2CHCl2)8(O2CEt)8(H2O)3] (6) have been obtained from the 1:1 reaction of the corresponding homocarboxylate species. Complexes 5 and 6 both contain a [Mn12O12] c

M. A. Baranov, M. S. Mar&#39;enko, Val. S. Rychkov, G. V. Shlyapnikov

We calculate the critical temperature of a superfluid phase transition in a polarized Fermi gas of dipolar particles. In this case the order parameter is anisotropic and has a nontrivial energy dependence. Cooper pairs do not have a definite value of the angular momentum and are coherent superpositions of all odd angular momenta. Our results describe prospec

A. Verdini, L. Floreano, F. Bruno, D. Cvetko

Self assembly on suitably chosen substrates is a well exploited root to control the structure and morphology, hence magnetization, of metal films. In particular, the Cu3Au(001) surface has been recently singled out as a good template to grow high spin Fe phases, due to the close matching between the Cu3Au lattice constant (3.75 Angstrom) and the equilibrium

Qingshan Yuan, Thilo Kopp

The two-dimensional Peierls-Hubbard model is studied at half-filling within both Hartree-Fork and Kotliar-Ruckenstein slave-boson theory. The interplay between two types of long-range order, bond-order wave (BOW) and antiferromagnetism (AFM), is analysed for two representative dimerization patterns, corresponding both to the same wavevector $(π,π)$. For each

Uwe C. Tauber, Vamsi K. Akkineni, Jaime E. Santos

We present an overview of the effects of detailed-balance violating perturbations on the universal static and dynamic scaling behavior near a critical point. It is demonstrated that the standard critical dynamics universality classes are generally quite robust: In systems with non-conserved order parameter, detailed balance is effectively restored at critica

Kenji Harada, Naoki Kawashima

Through Quantum Monte Carlo simulation, we study the biquadratic-interaction model with the SU(2) symmetry in two and three dimensions. The zero-temperature phase diagrams for the two cases are identical and exhibit an intermediate phase characterized by finite quadrupole moment, in agreement with mean-field type arguments and the semi-classical theory. In t

Beata Ziaja, David van der Spoel, Abraham Szoeke, Janos Hajdu

We have analyzed the cascade of secondary electrons in diamond and amorphous carbon generated by the thermalisation of a single Auger electron. The elastic electron mean free path was calculated as a function of impact energy in the muffin-tin potential approximation. The inelastic scattering cross section and the energy loss of the electron (expressed in te

Farhad H Jafarpour

A multi-species generalization of the Asymmetric Simple Exclusion Process (ASEP) has been considered in the presence of a single impurity on a ring. The model describes particles hopping in one direction with stochastic dynamics and hard core exclusion condition. The ordinary particles hop forward with their characteristic hopping rates and fast particles ca

Rama Govindarajan, Prabhu R. Nott, Sriram Ramaswamy

It is shown that a suspension of particles in a partially-filled, horizontal, rotating cylinder is linearly unstable towards axial segregation and an undulation of the free surface at large enough particle concentrations. Relying on the shear-induced diffusion of particles, concentration-dependent viscosity, and the existence of a free surface, our theory pr

D. R. Patton, C. J. Pritchet, R. G. Carlberg, R. O. Marzke

We investigate redshift evolution in the galaxy merger and accretion rates, using a well-defined sample of 4184 galaxies with 0.12 < z < 0.55 and R_C < 21.5. We identify 88 galaxies in close (5 < r_p < 20 h^{-1} kpc) dynamical (delta v < 500 km/s) pairs. These galaxies are used to compute global pair statistics, after accounting for selection effects resulti

My Ha Vuong, Laurent Cambresy, Nicolas Epchtein

We define a sample designed to select low-mass T Tauri stars and young brown dwarfs using DENIS data in the Chamaeleon II molecular cloud. We use a star count method to construct an extinction map of the Chamaeleon II cloud. We select our low-mass T Tauri star and young brown dwarf candidates by their strong infrared colour excess in the I-J/J-K_s colour-col

K. Rines, M. J. Geller, M. J. Kurtz, A. Diaferio

Using a redshift survey of 1779 galaxies and photometry from the 2-Micron All-Sky Survey (2MASS) covering 200 square degrees, we calculate independent mass and light profiles for the infall region of the Coma cluster of galaxies. The redshift survey is complete to $K_s=12.2$ (622 galaxies), 1.2 magnitudes fainter than $M^*_{K_s}$ at the distance of Coma. We

D. W. Koerner, A. I. Sargent, N. A. Ostroff

We present the first millimeter-wave aperture synthesis map of dust around a main sequence star. A 3&#39;&#39; resolution image of 1.3 mm continuum emission from Vega reveals a clump of emission 12&#39;&#39; from the star at PA 45 deg, consistent with the location of maximum 850 micron emission in a lower resolution JCMT/SCUBA map. The flux density is 4.0+/-

Jeffrey E. McClintock

We discuss new observations of X-ray novae with Chandra which provide strong evidence that black holes have event horizons. The evidence is based on the finding that black hole X-ray novae in quiescence are approximately 100 times fainter than equivalent neutron star X-ray novae. The advection-dominated accretion flow model provides a natural explanation for

Adam J. Burgasser

In this contribution, I discuss some of the salient features of L and T dwarf spectra in both the red optical (6300--10000 Å) and near-infrared (1--2.5 $\micron$) wavelength regimes. Important absorption bands and lines, including those of H$_2$O, CH$_4$, FeH, CrH, CO, and the alkali metal lines, are identified, and the development of recent classification s

G. L. Bosch, E. Terlevich, R. Terlevich

We have obtained accurate CCD narrow band H_beta and H_alpha photometry of Giant HII Regions in M 33, NGC 6822 and M 101. Comparison with previous determinations of emission line fluxes show large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion (sigma) derived from emission line widths w

P. Mazzotta, M. Markevitch, A. Vikhlinin, W. R. Forman

High-resolution Chandra images of several clusters of galaxies reveal sharp, edge-like discontinuities in their gas density. The gas temperature is higher in front of the edge where the density is low, corresponding to approximately continuous pressure across the edge. This new phenomenon was called ``cold fronts&#39;&#39;, to contrast it to shock fronts tha

L. J. Greenhill

Study of extragalactic H2O masers has progressed significantly in the 25 years since their discovery. Existing in star forming regions and in the accretion disks supermassive black holes, they are familiar and unfamiliar at the same time. A review of how our understanding has grown, up to the present day, is followed by comments on future prospects.

K. L. Rhode, W. Herbst, R. D. Mathieu

We have obtained high-dispersion spectra for 256 pre-main-sequence stars in the Orion Nebula Cluster in order to measure their projected rotational velocities and study the rotational evolution and physical properties of young, low-mass stars. Half the stars were chosen because they had known photometric periods and half were selected as a control sample of

L. Sidoli, T. Oosterbroek, A. N. Parmar, D. Lumb

We report the discovery of narrow X-ray absorption lines from the low-mass X-ray binary MXB1659-298 during an XMM-Newton observation in 2001 February. The 7.1 hr orbital cycle is clearly evident with narrow X-ray eclipses preceded by intense dipping activity. A sinusoid-like OM $B$-band modulation with a peak-to-peak modulation of 0.5 magnitude and a minimum

J. M. Fontenla, E. H. Avrett, R. Loeser

In this paper we have extended our previous modeling of energy balance in the chromosphere-corona transition region to cases with particle and mass flows. The cases considered here are quasi-steady, and satisfy the momentum and energy balance equations in the transition region. We include in all equations the flow velocity terms and neglect the partial deriv

Raven Kaldare, Matthew Colless, Somak Raychaudhury, Bruce A. Peterson

The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of 4613 galaxies brighter than $\bJ = 16.7$ (corrected for Galactic extinction) over a 605 sq. degree region of sky in the general direction of the Local Group motion. The survey region is an approximately $60\degr \times 10\degr$ strip spanning the sky from the Shapley Supercluster to the Hy

J. D. Barrow, H. B. Sandvik, J. Magueijo

We determine the behaviour of a time-varying fine structure &#39;constant&#39; $α(t)$ during the early and late phases of universes dominated by the kinetic energy of changing $α(t)$, radiation, dust, curvature, and lambda, respectively. We show that after leaving an initial vacuum-dominated phase during which $α$ increases, $α$ remains constant in universes

B. Stelzer, V. Burwitz, R. Neuhaeuser, M. Audard

We have observed the flare star YY Gem simultaneously with XMM-Newton and Chandra as part of a multi-wavelength campaign aiming at a study of variability related to magnetic activity in this short-period eclipsing binary. Here we report on the first results from the analysis of the X-ray spectrum. The vicinity of the star provides high enough S/N in the CCD

Stefano Covino, Filippo Zerbi, Guido Chincarini, Marcello Rodono&#39;

The main goal of the REM project is the observation of prompt afterglow of Gamma-Ray Burst (GRB) events. Such observations at Near InfraRed (NIR) wavelengths are even very promising, since they allow to monitor high-z Ly-$α$ absorbed bursts as well as events occurring in dusty star-forming regions. In addition to GRB science, a large amount of time ($\sim 40

S. Covino, G. Tagliaferri, E. Bertone, G. Cutispoto

We discuss ROSAT, ASCA, {\it Beppo}SAX and optical observations of the young active star Gl 355. During the ROSAT observation a strong flare was detected with a peak flux more than an order of magnitude larger than the quiescent level. Spectral analysis of the data allows us to study the temperature and emission measure distribution, and the coronal metal ab

M. Bureau, R. Bacon, M. Cappellari, Y. Copin

A summary of the SAURON project and its current status is presented. SAURON is a panoramic integral-field spectrograph designed to study the stellar kinematics, gaseous kinematics, and stellar populations of spheroids. Here, the sample of galaxies and its properties are described. The instrument is detailed and its capabilities illustrated through observatio

M. Rejkuba, D. Minniti, F. Courbin, D. R. Silva

We used the direct CCD camera at the Magellan I telescope at Las Campanas Observatory and FORS1 at Antu VLT at ESO Paranal Observatory to image fields centered on the inner and outer optical filaments in the halo of NGC 5128. In the V vs. U-V color-magnitude diagrams we have identified young blue supergiants associated with these line-emitting filaments loca

M. Rejkuba, D. Minniti, D. R. Silva, T. R. Bedding

We resolve stars of the nearest giant elliptical galaxy NGC 5128 using VLT with FORS1 and ISAAC. We construct deep U, V and Ks color-magnitude and color-color diagrams in two different halo fields (in the halo and in the north-eastern diffuse shell). In the outer, shell field, at ~14 kpc from the center of the galaxy, there is a significant recent star forma

Jason A. Surace, David B. Sanders, Aaron S. Evans

Ground-based high spatial-resolution (FWHM < 0.3-0.8&#34;) optical and near-infrared imaging (0.4-2.2um) is presented for a complete sample of optically selected Palomar-Green QSOs with far-infrared excesses at least as great as those of &#34;warm&#34; AGN-like ultraluminous infrared galaxies (L_ir/L_big-blue-bump > 0.46). In all cases, the host galaxies of

T. Contini, M. A. Treyer, M. Sullivan, R. S. Ellis

We discuss the chemical properties of a sample of UV-selected intermediate-redshift (0 < z < 0.4) galaxies in the context of their physical nature and star formation history. This work represents an extension of our previous studies (Treyer et al. 1998; Sullivan et al. 2000, 2001) on UV-selected galaxies. We revisit the optical spectra of these galaxies and

J. L. Gomez

The recent improvement in VLBI arrays is providing information of the emission and magnetic field structure of relativistic jets, both extragalactic and galactic (microquasars), with unprecedented spatial and temporal resolution. These observations are revealing the importance of the hydrodynamical processes that govern the jet evolution, which can be studie

Torsten Bringmann, Claus Kiefer, David Polarski

We review the formalism of primordial black holes (PBHs) production and show that the mass variance at horizon crossing has been systematically overestimated in previous studies. We derive the correct expression. The difference is maximal at the earliest formation times and still very significant for PBH masses $\sim 10^{15}$g, an accurate estimate requiring

Benoit B. Mandelbrot, Boaz Kol, Amnon Aharony

When suitably rescaled, the distribution of the angular gaps between branches of off-lattice radial DLA is shown to approach a size-independent limit. The power-law expected from an asymptotic fractal dimension D=1.71 arises only for very small angular gaps, which occur only for clusters significantly larger than one million particles. Intermediate size gaps

Masatoshi Sato, Toshiaki Tanaka

We investigate particular models which can be N-fold supersymmetric at specific values of a parameter in the Hamiltonians. The models to be investigated are a periodic potential and a parity-symmetric sextic triple-well potential. Through the quantitative analyses on the non-perturbative contributions to the spectra by the use of the valley method, we show h

Artur Avila

We analyze the infinitesimal effect of holomorphic perturbations of the dynamics of a structurally stable rational map on a neighborhood of its Julia set. This implies some restrictions on the behavior of critical points.

Alexei V. Filippenko

Nearly 4 years ago, two teams of observational astronomers reported that high-redshift Type Ia supernovae are fainter than expected in a decelerating or freely coasting universe. The radical conclusion that the universe has been accelerating in the past few billion years, possibly because of a nonzero value for Einstein&#39;s cosmological constant, has gripp

J. Daniel Christensen, William G. Dwyer, Daniel C. Isaksen

Many examples of obstruction theory can be formulated as the study of when a lift exists in a commutative square. Typically, one of the maps is a cofibration of some sort and the opposite map is a fibration, and there is a functorial obstruction class that determines whether a lift exists. Working in an arbitrary pointed proper model category, we classify th

A. Loinger

A good candidate to the role of passive gravitational mass of a Schwarzschild&#39;s incompressible sphere is represented by the substantielle Masse of the sphere, which is larger than the active gravitational mass. Presumably this inequality has a general validity, i.e. it is not limited to the homogeneous spheres of incompressible fluids.

Juan C. Migliore, Rosa Miró-Roig

We consider the minimal free resolution of a generic set of n+1 forms (not necessarily of the same degree) in a polynomial ring of n variables. The Hilbert function for such an ideal is known, thanks to a result of Stanley and of Watanabe. (For more than n+1 forms the Hilbert function is conjectured by Froberg.) However, in all but a few trivial cases, the r

Zhongmin Shen

It is the Hilbert&#39;s Fourth Problem to characterize the (not-necessarily-reversible) distance functions on a bounded convex domain in R^n such that straight lines are shortest paths. Distance functions induced by a Finsler metric are regarded as smooth ones. Finsler metrics with straight geodesics said to be projective. It is known that the flag curvature