784 research outputs found
Renormalized Wick expansion for a modified PQCD
The renormalization scheme for the Wick expansion of a modified version of
the perturbative QCD introduced in previous works is discussed. Massless QCD is
considered, by implementing the usual multiplicative scaling of the gluon and
quark wave functions and vertices. However, also massive quark and gluon
counter-terms are allowed in this mass less theory since the condensates are
expected to generate masses. A natural set of expansion parameters of the
physical quantities is introduced: the coupling itself and to masses and
associated to quarks and gluons respectively. This procedure allows to
implement a dimensional transmutation effect through these new mass scales. A
general expression for the new generating functional in terms of the mass
parameters and is obtained in terms of integrals over arbitrary but
constant gluon or quark fields in each case. Further, the one loop potential,
is evaluated in more detail in the case when only the quark condensate is
retained. This lowest order result again indicates the dynamical generation of
quark condensates in the vacuum.Comment: 13 pages, one figur
About the phase space of SL(3) Black Holes
In this note we address some issues of recent interest, related to the
asymptotic symmetry algebra of higher spin black holes in
Chern Simons (CS) formulation. We
compute the fixed time Dirac bracket algebra that acts on two different phase
spaces. Both of these spaces contain black holes as zero modes. The result for
one of these phase spaces is explicitly shown to be isomorphic to
in first order perturbations.Comment: improved presentatio
Black Holes in the 3D Higher Spin Theory and Their Quasi Normal Modes
We present a class of 3D Black Holes based on flat connections which are
polynomials in the BTZ -valued connection. We
solve analytically the fluctuation equations of matter in their background and
find the spectrum of their Quasi Normal Modes. We analyze the bulk to boundary
two-point functions. We also relate our results and those arising in other
backgrounds discussed recently in the literature on the subject.Comment: v3: typo corrected in first line of Eq (4.2), improved presentatio
Els centre de recursos per a l'aprenentatge i la investigació (CRAI): obrint pas a noves aliances i oportunitats
Partition Function of Gauge Theories on a Squashed with Isometry
We study supersymmetric gauge theories on a large family of squashed
4-spheres preserving isometry and determine the
conditions under which this background is supersymmetric. We then compute the
partition function of the theories by using localization technique. The results
indicate that for SUSY, including both vector-multiplets and
hypermultiplets, the partition function is independent of the arbitrary
squashing functions as well as of the other supergravity background fields.Comment: version to appear in Nuclear Physics
Coastal salina evaporites of the Triassic-Liassic boundary in the Iberian Peninsula : the Alacón borehole
The evaporite unit (the Lécera Formation), which was formed at the Triassic-Liassic boundary in the Aragonian Branch of the Iberian Chain, was studied at the 01 Alacón borehole (Alacón village, Teruel province), where it is mainly constituted by a thick (>300 m) succession of predominant sulphates (anhydrite, secondary gypsum and carbonate) overlain by brecciated carbonates. In the evaporite succession, a number of lithofacies were recognized, which can be grouped into an "ideal cycle", from base to top: (C1) massive to banded carbonate mudstone, (C2) alternation of carbonate and anhydrite laminae, (A1) alternation of anhydrite and carbonate bands, (A2) clastic intercalations in the alternation of anhydrite and carbonate bands, (A3) laminated to banded anhydrite, (A4) bedded pseudomorphs, (A5) interstitial pseudomorphs, and (A6) massive to nodular anhydrite. Fine-grained gypsum (anhydrite laminae and bands), bedded selenitic gypsum (bedded pseudomorphs), interstitial selenitic gypsum (interstitial pseudomorphs), and graded-nodular anhydrite (a particular fabric of nodular anhydrite) were the most outstanding depositional lithofacies. The evaporite succession exhibits a marked cyclicity: in the lower part the individual cycles are more similar to the ideal cycle and reflect deeper water settings, whereas in the upper part they correspond to shallower water settings. The evaporite sedimentation mainly occurred in a subsiding coastal basin of the salina or lagoon type. In this setting, the subaqueous precipitation of the carbonate and gypsum lithofacies was followed, in each cycle, by the interstitial growth of anhydrite in exposed conditions. As a whole, the evaporite succession reflects an infilling process. The conversion into anhydrite of the selenitic gypsum -probably also of the rest of depositional gypsum lithofaciesstarted under synsedimentary conditions and followed during shallow to moderate burial diagenesis
Dilaton stabilization by massive fermion matter
The study started in a former work about the Dilaton mean field stabilization
thanks to the effective potential generated by the existence of massive
fermions, is here extended. Three loop corrections are evaluated in addition to
the previously calculated two loop terms. The results indicate that the Dilaton
vacuum field tend to be fixed at a high value close to the Planck scale, in
accordance with the need for predicting Einstein gravity from string theory.
The mass of the Dilaton is evaluated to be also a high value close to the
Planck mass, which implies the absence of Dilaton scalar signals in modern
cosmological observations. These properties arise when the fermion mass is
chosen to be either at a lower bound corresponding to the top quark mass, or
alternatively, at a very much higher value assumed to be in the grand
unification energy range. One of the three 3-loop terms is exactly evaluated in
terms of Master integrals. The other two graphs are however evaluated in their
leading logarithm correction in the perturbative expansion. The calculation of
the non leading logarithmic contribution and the inclusion of higher loops
terms could made more precise the numerical estimates of the vacuum field value
and masses, but seemingly are expected not to change the qualitative behavior
obtained. The validity of the here employed Yukawa model approximation is
argued for small value of the fermion masses with respect to the Planck one. A
correction to the two loop calculation done in the previous work is here
underlined.Comment: 18 pages, 5 figures, the study was extended and corrections on the
former calculations and redaction were done. The paper had been accepted for
publication in "Astrophysics and Space Science
Impacto del envejecimiento en el seguro
Màster de Direcció d'Entitats Asseguradores i Financeres, Universitat de Barcelona, Facultat d'Economia i Empresa, Curs: 2003-2004, Tutor: Juan Ignacio GuerreroEl Impacto del Envejecimiento en España actualmente es uno de los temas más cruciales desde el punto de vista Económico, Demográfico y Social. Donde el Sector Asegurador debe asumir un papel importante.
Por ello, es necesario que nuestra generación adopte una serie de medidas y establezca las bases para garantizar un nivel de vida digno, para nuestros mayores
Remark on charge conjugation in the non relativistic limit
We study the non relativistic limit of the charge conjugation operation in the context of the Dirac equation coupled to an electromagnetic field.
The limit is well defined and, as in the relativistic case, ,
(parity) and (time reversal) are the generators of a matrix group
isomorphic to a semidirect sum of the dihedral group of eight elements and
. The existence of the limit is supported by an argument based in quantum
field theory. Also, and most important, the limit exists in the context of
galilean relativity. Finally, if one complexifies the Lorentz group and
therefore the galilean spacetime , then the explicit form of the matrix
for allows to interpret it, in this context, as the complex
conjugation of the spatial coordinates: . This result is
natural in a fiber bundle description.Comment: 8 page
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