Angular Structure of the In-Medium QCD Cascade.

We study the angular broadening of a medium-induced QCD cascade. We derive the equation that governs the evolution of the average transverse momentum squared of the gluons in the cascade as a function of the medium length, and we solve this equation analytically. Two regimes are identified. For a medium of a not too large size, and for not too soft gluons, the transverse momentum grows with the size of the medium according to standard momentum broadening. The other regime, visible for a medium of a sufficiently large size and very soft gluons, is a regime dominated by multiple branchings: there, the average transverse momentum saturates to a value that is independent of the size of the medium. This structure of the in-medium QCD cascade is, at least qualitatively, compatible with the recent LHC data on dijet asymmetry.

A test of the nature of cosmic acceleration using galaxy redshift distortions.

Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this 'dark energy' corresponds to a 'cosmological constant', perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a measurement of this effect at a redshift of 0.8. Using a new survey of more than 10,000 faint galaxies, we measure the anisotropy parameter beta = 0.70 +/- 0.26, which corresponds to a growth rate of structure at that time of f = 0.91 +/- 0.36. This is consistent with the standard cosmological-constant model with low matter density and flat geometry, although the error bars are still too large to distinguish among alternative origins for the accelerated expansion. The correct origin could be determined with a further factor-of-ten increase in the sampled volume at similar redshift.

Medium-induced QCD cascade: democratic branching and wave turbulence.

We study the average properties of the gluon cascade generated by an energetic parton propagating through a quark-gluon plasma. We focus on the soft, medium-induced emissions which control the energy transport at large angles with respect to the leading parton. We show that the effect of multiple branchings is important. In contrast with what happens in a usual QCD cascade in vacuum, medium-induced branchings are quasidemocratic, with offspring gluons carrying sizable fractions of the energy of their parent gluon. This results in an efficient mechanism for the transport of energy toward the medium, which is akin to wave turbulence with a scaling spectrum ~1/sqrt[ω]. We argue that the turbulent flow may be responsible for the excess energy carried by very soft quanta, as revealed by the analysis of the dijet asymmetry observed in Pb-Pb collisions at the LHC.

Nonperturbative renormalization group preserving full-momentum dependence: implementation and quantitative evaluation.

We present the implementation of the Blaizot-Méndez-Wschebor approximation scheme of the nonperturbative renormalization group we present in detail, which allows for the computation of the full-momentum dependence of correlation functions. We discuss its significance and its relation with other schemes, in particular, the derivative expansion. Quantitative results are presented for the test ground of scalar O(N) theories. Besides critical exponents, which are zero-momentum quantities, we compute the two-point function at criticality in the whole momentum range in three dimensions and, in the high-temperature phase, the universal structure factor. In all cases, we find very good agreement with the best existing results.

Solutions of renormalization-group flow equations with full momentum dependence.

We demonstrate the power of a recently proposed approximation scheme for the nonperturbative renormalization group that gives access to correlation functions over their full momentum range. We solve numerically the leading-order flow equations obtained within this scheme and compute the two-point functions of the O(N) theories at criticality, in two and three dimensions. Excellent results are obtained for both universal and nonuniversal quantities at modest numerical cost.

Transverse energy fluctuations and the pattern of J/psi suppression in Pb-Pb collisions.

The NA50 Collaboration has recently observed that the J/psi production rate in Pb-Pb collisions decreases more rapidly as a function of the transverse energy for the most central collisions than for less central ones. We show that this phenomenon can be understood as an effect of transverse energy fluctuations in central collisions. A good fit of the data is obtained using a model which relates J/psi suppression to the local energy density. Our results suggest that the J/psi is completely suppressed at the highest densities achieved in Pb-Pb collisions.

Nonanalytic dependence of the transition temperature of the homogeneous dilute Bose gas on scattering length.

We show that the shift in the transition temperature of the dilute homogeneous Bose gas is nonanalytic in the scattering amplitude a. The first correction beyond the positive linear shift in a is negative and of order a(2)lna. This nonuniversal nonanalytic structure indicates how the discrepancies between numerical calculations at finite a can be reconciled with calculations of the limit a-->0, since the linearity is apparent only for anomalously small a.

[Adrenal cortex and avitaminosis A: II. Complementary in vivo and in vitro studies on inhibition of corticoidogenesis in moderate deficiency in the rat. III. In vivo criterion for activity: glycemic response to ACTH]. / Corticosurrénale et avitaminose A: II. Compléments a l'étude in vivo et in vitro; modalités d'inhibition de la corticoidogenèse en carence modérée chez le rat. III. Recherche d'un critère d'activité utilisable in vivo; réponse glycémique a l'ACTH

II. We set up new experiments, both in vivo and in vitro, in order to explain the impaired adrenal response to stress, of vitamin A middly deficient, male Wistar rats. Injections of progesterone, 6 mg s.c. or i.p. every other day, did not improve the deficiency curse in our rats. In agreement with these results, we have found that, in vitro, the delta5-3beta hydroxysteroide dehydrogenase is not altered in deficient glands; we confirmed it histochemically. On the other hand, the 11beta and 18 hydroxylase activities are lowered in vitro (and presumably in vivo). When conditions of hyperactivity are established, the conversion of deoxycorticosterone (DOC) to 18 OH-DOC or to corticosterone is reduced and DOC accumulates in the incubation medium. III. When middly deficient intact rats are injected with ACTH i.p. (2UI p. 100 g of body weight), only some of them are found to have normoglycemia or hyperglycemia, 45 or 60 minutes after injection, as the controls do. Many deficient rats become hypoglycemic as the adrenalectomised animals do. We think that the changes in the glycemia after ACTH injection could be used to discriminate between the more or less deficient rats.