619 research outputs found
Aspects of Quantum Fermionic T-duality
We study two aspects of fermionic T-duality: the duality in purely fermionic
sigma models exploring the possible obstructions and the extension of the
T-duality beyond classical approximation. We consider fermionic sigma models as
coset models of supergroups divided by their maximally bosonic subgroup
OSp(m|n)/SO(m) x Sp(n). Using the non-abelian T-duality and a non-conventional
gauge fixing we derive their fermionic T-duals. In the second part of the
paper, we prove the conformal invariance of these models at one and two loops
using the Background Field Method and we check the Ward Identities.Comment: 65 pages, 5 figure
Electromagnetic response of strongly coupled plasmas
We present a thorough analysis of the electromagnetic response of strongly
coupled neutral plasmas described by the gauge/gravity correspondence. The
coupling of the external electromagnetic field with the tower of quasi-normal
modes of the plasmas supports the presence of various electromagnetic modes
with different properties. Among them we underline the existence of negative
refraction with low dissipation for a transverse non-hydrodynamical mode.
Previous hydrodynamical approaches have shown the ubiquitous character of
negative refraction in charged plasmas and the absence thereof in neutral
plasmas. Our results here extend the analysis for neutral plasmas beyond the
hydrodynamical regime. As an application of these new insights we briefly
discuss the case of the quark gluon plasma in the temperature dominated regime.Comment: 29 pages, 15 figure
Analytic pseudo-Goldstone bosons
We consider the interplay between explicit and spontaneous symmetry breaking
in strongly coupled field theories. Some well-known statements, such as the
Gell-Mann-Oakes-Renner relation, descend directly from the Ward identities and
have thus a general relevance. Such Ward identities are recovered in
gauge/gravity dual setups through holographic renormalization. In a simple
paradigmatic three dimensional toy-model, we find analytic expressions for the
two-point correlators which match all the quantum field theoretical
expectations. Moreover, we have access to the full spectrum, which is
reminiscent of linear confinement.Comment: 20 pages, 4 figures, v2 minor correction
A Note on Holographic Non-Relativistic Goldstone Bosons
We consider a holographic set-up where relativistic invariance is broken by a
chemical potential, and a non-abelian internal symmetry is broken
spontaneously. We use the tool of holographic renormalization in order to infer
what can be learned purely by analytic boundary considerations. We find that
the expected Ward identities are correctly reproduced. In particular, we obtain
the identity which implies the non-commutation of a pair of broken charges,
which leads to the presence of Goldstone bosons with quadratic dispersion
relations.Comment: 13+7 pages, no figures; v2: added clarification on vanishing chemical
potential, version to appear in journa
Fermionic Wigs for BTZ Black Holes
We compute the wig for the BTZ black hole, namely the complete non-linear
solution of supergravity equations with all fermionic zero modes. We use a
"gauge completion" method starting from AdS_3 Killing spinors to generate the
gravitinos fields associated to the BH and we compute the back-reaction on the
metric. Due to the anticommutative properties of the fermionic hairs the
resummation of these effects truncates at some order. We illustrate the
technique proposed in a precedent paper in a very explicit and analytical form.
We also compute the mass, the angular momentum and other charges with their
corrections.Comment: 11 pages, no figure
Fermionic Corrections to Fluid Dynamics from BTZ Black Hole
We reconstruct the complete fermionic orbit of the non-extremal BTZ black
hole by acting with finite supersymmetry transformations. The solution
satisfies the exact supergravity equations of motion to all orders in the
fermonic expansion and the final result is given in terms of fermionic
bilinears. By fluid/gravity correspondence, we derive linearized Navier-Stokes
equations and a set of new differential equations from Rarita-Schwinger
equation. We compute the boundary energy-momentum tensor and we interpret the
result as a perfect fluid with a modified definition of fluid velocity.
Finally, we derive the modified expression for the entropy of the black hole in
terms of the fermionic bilinears.Comment: 21 pages, Latex2e, no figure
Vitrification of In Vitro Produced Porcine Blastocysts: Influence of Cryoprotectants Toxicity and Embryo Age
Background: Porcine embryos are sensible to all assisted reproduction manipulations, especially the ones that involve cryopreservation. Despite the high cryoprotectant concentrations routinely applied, vitrification is the most effective technique to date. These substances toxicity can also play a negative role in embryo viability. During in vitro porcine embryo production, the speed of development is often unevenly distributed. It is possible that their development speed, affects embryo tolerance to cryoprotectants. This study aimed to evaluate the toxicity of porcine embryos of days 5 or 6 of culture to cryoprotectant agents; as well as to assess embryo survival to vitrification.Material, Methods & Results: Parthenogenetic porcine blastocysts and expanded blastocysts of days 5 and 6 of culture were exposed to toxicity tests (experiments 1 and 2) and vitrification (experiment 3) using different protocols. In the first experiment, three different cryoprotectants were used (Dimethyl sulfoxide - DMSO, Ethylene glycol – EG, and Sucrose - SUC), combined in three different associations (G1: 15% EG + 15% DMSO with 0.5M SUC; G2: 16% EG + 16% DMSO with 0.4M SUC; G3: 18% EG + 18% DMSO with 0.5M SUC). In the fresh Control, embryos of day 6 are more sensible than the ones of day 5, whom showed a lower hatching rate (39.7 vs. 60.8%). After the toxicity (Experiment 1) test, the G1 showed better expansion rates in day 6 (50.0 vs 31.0 and 3.6% for G2 and G3) and higher hatching of day 6 compared to G2 and G3 (23.2, vs. 8.6 and 0.0% for G2 and G3). The fresh non hatched embryos at day 8, derived at day 6, had a lower percentage of cells with cleaved caspase-3 (20.2%) compared with the G1 (30.5%), G2 (31.4%) and G3 (30.5%). The hatched embryos of day 5 from G2 had lower total cell number (TCN) compared with the day 6 hatched embryos, whereas in G1 the TCN was not affected. The second experiment compared EG combined to one of these three extracellular cryoprotectants: Polyvinylpyrrolidone/sucrose/trehalose (respectively groups: PVP, SUC, TRE). The group SUC has raised the best results for day 5 embryos, whereas for day 6 embryos SUC and TRE were both best. The third experiment tested four vitrification protocols, being P1: EG+DMSO+TRE/warming with SUC; P2: EG+DMSO+TRE/warming TRE; P3: EG+TRE/ warming SUC; P4: EG+TRE/warming TRE. The expansion of vitrified day 5 embryos was higher in the P1 (20.0%) in comparison with the other three groups (4.3, 4.3 and 4.4% for P2, P3 and P4, respectively), with no difference for their hatching rates, been it lower comparing to the Control. Day 6 embryos showed no difference in expansion and hatching for the vitrified groups, been them lower than the Control.Discussion: Embryos obtained on day 6 are more sensible than the ones of day 5, fact observed when the embryos were exposed to cryoprotectant solution, as well by the behavior of the no treated Control embryos. The toxicity increases as it does the concentration of intracellular cryoprotectant, where over 16% of the intracellular cryoprotectors already affected the day 6 embryos development. For the day 5 embryos however, 15 or 16% of the intracellular cryoptrotectors, had similar behavior to the embryos. For the extracellular solutions, however, it is variable according the embryos development speed. Indeed, it is necessary to adjust the cryoprotectors to be used to cryopreserve porcine in vitro produced embryos obtained at days 5 and 6 of culture
Fermions, Wigs, and Attractors
We compute the modifications to the attractor mechanism due to fermionic
corrections. In N=2, D=4 supergravity, at the fourth order, we find a new
contribution to the horizon values of the scalar fields of the vector
multiplets.Comment: v2 : 1+11 pages; paper reorganized in Sections; Sec. 5 added, with
detailed treatment of the axion-dilaton model; some typos fixed and
references adde
No Fermionic Wigs for BPS Attractors in 5 Dimensions
We analyze the fermionic wigging of 1/2-BPS (electric) extremal black hole
attractors in N=2, D=5 ungauged Maxwell-Einstein supergravity theories, by
exploiting anti-Killing spinors supersymmetry transformations. Regardless of
the specific data of the real special geometry of the manifold defining the
scalars of the vector multiplets, and differently from the D=4 case, we find
that there are no corrections for the near--horizon attractor value of the
scalar fields; an analogous result also holds for 1/2-BPS (magnetic) extremal
black string. Thus, the attractor mechanism receives no fermionic corrections
in D=5 (at least in the BPS sector).Comment: 24 pages, LaTeX2
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