6,329 research outputs found
A method for solve integrable spin chains combining different representations
A non homogeneous spin chain in the representations and
of is analyzed. We find that the naive nested Bethe ansatz is not
applicable to this case. A method inspired in the nested Bethe ansatz, that can
be applied to more general cases, is developed for that chain. The solution for
the eigenvalues of the trace of the monodromy matrix is given as two coupled
Bethe equations different from that for a homogeneous chain. A conjecture about
the form of the solutions for more general chains is presented.
PACS: 75.10.Jm, 05.50+q 02.20 SvComment: PlainTeX, harvmac, 13 pages, 3 figures, to appear in Phys. Rev.
On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344
The main goal of this study is to carry out a spatially resolved
investigation of the warm interstellar medium (ISM) in the extremely metal-poor
Blue Compact Dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on the
analysis of the spatial distribution of chemical abundances, emission-line
ratios and kinematics of the ISM, and to the recent star-forming activity in
this galaxy. This study is based on optical integral field unit spectroscopy
data from Gemini Multi-Object Spectrograph at the Gemini North telescope and
archival Sloan Digital Sky Survey images. The data were obtained in two
different positions across the galaxy, obtaining a total 4 arcsec X 8 arcsec
field which encompasses most of its ISM. Emission-line maps and broad-band
images obtained in this study indicate that HS 2236+1344 hosts three Giant HII
regions. Our data also reveal some faint curved features in the BCD periphery
that might be due to tidal perturbations or expanding ionized-gas shells. The
ISM velocity field shows systematic gradients along the major axis of the BCD,
with its south-eastern and north-western half differing by ~80 km/s in their
recessional velocity. The Ha and Hb equivalent width distribution in the
central part of HS 2236+1344 is consistent with a very young (~3 Myr) burst.
Our surface photometry analysis indicates that the ongoing starburst provides
~50% of the total optical emission, similar to other BCDs. It also reveals an
underlying lower-surface brightness component with moderately red colors, which
suggest that the galaxy has undergone previous star formation. We derive an
integrated oxygen abundance of 12+log(O/H)=7.53\pm0.06 and a nitrogen-to-oxygen
ratio of log(N/O)=-1.57\pm0.19. Our results are consistent, within the
uncertainties, with a homogeneous distribution of oxygen and nitrogen within
the ISM of the galaxy. (abridged)Comment: 15 pages, 16 figures, accepted for publication in A&
Spinor techniques for massive fermions with arbitrary polarization
We present a new variant of the spinor techniques for calculating the
amplitudes of processes involving massive fermions with arbitrary polarization.
It is relatively simple and leads to basic spinor products. Our procedure is
not more complex than CALCUL spinor techniques for massless fermions. We obtain
spinor Chisholm identities for massive fermions. As an illustration,
expressions are given for the amplitudes of electron-positron annihilation into
fermions-pairs for several polarizations.Comment: 14 pages, 2 figure
An atlas of Calcium triplet spectra of active galaxies
We present a spectroscopic atlas of active galactic nuclei covering the
region around the 8498, 8542, 8662 Calcium triplet (CaT) lines. The sample
comprises 78 objects, divided into 43 Seyfert 2s, 26 Seyfert 1s, 3 Starburst
and 6 normal galaxies. The spectra pertain to the inner ~300 pc in radius, and
thus sample the central kinematics and stellar populations of active galaxies.
The data are used to measure stellar velocity dispersions (sigma_star) both
with cross-correlation and direct fitting methods. These measurements are found
to be in good agreement with each-other and with those in previous studies for
objects in common. The CaT equivalent width is also measured. We find average
values and sample dispersions of W_CaT of 4.6+/-2.0, 7.0 and 7.7+/-1.0
angstrons for Seyfert 1s, Seyfert 2s and normal galaxies, respectively. We
further present an atlas of [SIII]\lambda 9069 emission line profiles for a
subset of 40 galaxies. These data are analyzed in a companion paper which
addresses the connection between stellar and Narrow Line Region kinematics, the
behaviour of the CaT equivalent width as a function of sigma_star, activity
type and stellar population properties.Comment: 18 pages, 10 figures, accepted for publication in MNRA
Rigidly Rotating Strings in Stationary Spacetimes
In this paper we study the motion of a rigidly rotating Nambu-Goto test
string in a stationary axisymmetric background spacetime. As special examples
we consider the rigid rotation of strings in flat spacetime, where explicit
analytic solutions can be obtained, and in the Kerr spacetime where we find an
interesting new family of test string solutions. We present a detailed
classification of these solutions in the Kerr background.Comment: 19 pages, Latex, 9 figures, revised for publication in Classical and
Quantum Gravit
La cohesión y la seguridad ciudadana : un enfoque global
El artículo revisa el concepto de cohesión social y la noción de seguridad, partiendo del análisis de los profundos desequilibrios y desigualdades sociales que el modelo económico dominante a escala global desde los años 1980 crea o intensifica en América Latina. Centrado en las transformaciones que generaron la pérdida de confianza en las instituciones, en el Estado, en el mercado del trabajo, en la educación, incluso en la religión y en la familia, sobre las cuales reposaba la solidaridad orgánica en el marco de la sociedad industrial capitalista, examina cinco indicadores de la existencia de problemas de inseguridad en relación con la cohesión social. Pone de relieve que el problema de la inseguridad se asocia con la ruptura o la fragilidad de los mecanismos de integración y de mediación social y sostiene la
necesidad de reconstruir la cohesión social para alcanzar la seguridad ciudadana, destacando que este proceso se funda en una profunda modificación política, económica y social enfocada en la inclusión social, de la que son co-responsables el Estado y los ciudadanos como actores de su propio desarrollo.The article reviews the concept of social cohesion and the notion of security, based on deep analysis of the imbalances and inequalities that the dominant economic model on a global scale since 1980 creates or intensifies in Latin America. Focused on the changes that generated a loss of confidence in institutions in the state, labor market, education, even religion and family, on which rested the organic solidarity within society industrial capitalism, examines five indicators of the existence of problems of insecurity in relation to social cohesion. Highlights that the problem of insecurity is associated with the break or fragility of the mechanisms of social integration and mediation and supports the need to rebuild social cohesion to achieve security, noting that this process is based on profound political change, economic
and social focus on social inclusion, of which are co-responsible for the state and citizens as actors in their own development.Fil: Klein, Juan Luis.
Université du Québec (Canadá)Fil: Enríquez, D..
Université du Québec (Canadá)Fil: Vega, R. V..
Université du Québec (Canadá
Multiflavor Correlation Functions in non-Abelian Gauge Theories at Finite Density in two dimensions
We compute vacuum expectation values of products of fermion bilinears for
two-dimensional Quantum Chromodynamics at finite flavored fermion densities. We
introduce the chemical potential as an external charge distribution within the
path-integral approach and carefully analyse the contribution of different
topological sectors to fermion correlators. We show the existence of chiral
condensates exhibiting an oscillatory inhomogeneous behavior as a function of a
chemical potential matrix. This result is exact and goes in the same direction
as the behavior found in QCD_4 within the large N approximation.Comment: 28 pages Latex (3 pages added and other minor changes) to appear in
Phys.Rev.
Strings in Cosmological and Black Hole Backgrounds: Ring Solutions
The string equations of motion and constraints are solved for a ring shaped
Ansatz in cosmological and black hole spacetimes. In FRW universes with
arbitrary power behavior [R(X^0) = a\;|X^0|^{\a}\, ], the asymptotic form of
the solution is found for both and and we plot the
numerical solution for all times. Right after the big bang (), the
string energy decreasess as and the string size grows as for . Very
soon [ ] , the ring reaches its oscillatory regime with frequency
equal to the winding and constant size and energy. This picture holds for all
values of \a including string vacua (for which, asymptotically, \a = 1).
In addition, an exact non-oscillatory ring solution is found. For black hole
spacetimes (Schwarzschild, Reissner-Nordstr\oo m and stringy), we solve for
ring strings moving towards the center. Depending on their initial conditions
(essentially the oscillation phase), they are are absorbed or not by
Schwarzschild black holes. The phenomenon of particle transmutation is
explicitly observed (for rings not swallowed by the hole). An effective horizon
is noticed for the rings. Exact and explicit ring solutions inside the
horizon(s) are found. They may be interpreted as strings propagating between
the different universes described by the full black hole manifold.Comment: Paris preprint PAR-LPTHE-93/43. Uses phyzzx. Includes figures. Text
and figures compressed using uufile
Excitations and S-matrix for su(3) spin chain combining and ${3^{*}}
The associated Hamiltonian for a su(3) spin chain combining and
representations is calculated. The ansatz equations for this chain
are obtained and solved in the thermodynamic limit, and the ground state and
excitations are described. Thus, relations between the number of roots and the
number of holes in each level have been found . The excited states are
characterized by means of these quantum numbers. Finally, the exact S matrix
for a state with two holes is found.Comment: 17 pages, plaintex, harvmac (to be published in J. of Phys. A
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