12C(e,e′ p) missing momentum distributions in HF-Sk3 and RPA-Sk3 continuum theories

We study the momentum distribution or reduced cross-section for electron induced 1p _3/2 proton knockout from¹²C in parallel kinematics. We refer to continuum self-consistent HF-Sk 3 and RPA-Sk 3 theories with a full treatment of the one-nucleon energy continuum. The PWIA limit is also shown. The¹²C(e, e′p ₀) missing momentum distribution is analyzed in connection with the energy dependence at fixed momentum transfer of the¹²C(e, e′) longitudinal and transverse responses. We compare our theoretical results with the available experimental data.     

Critical-point limit law for Temperley's continuous model

We consider the probability distribution of the volumeV _N in aN-particle Temperley's model of liquid-gas condensation. We rigorously prove that the critical-point limit law of (V _N-Nv_c)/N ^3/4 exists and has probability density proportional to exp(-cx⁴) (c > 0). This result shows that the probabilistic approach to critical phenomena may be extended to continuous fluid systems.     

Shape of an amorphous metallic ribbon during annealing: A kinetic study

We have measured the curvature of an amorphous metallic ribbon (alloy Fe_72.5 Cr_6.5 P_13.2 C_7.8) as a function of time for several annealing temperatures. The change in curvature is due to different structural relaxations of the two sides of the ribbon. The data lead to a rather narrow distribution of activation energies, centered around E_eff ∼ 1.0 eV and to a limit frequency in the range 3.10³–3.10⁵ Hz, which is discussed at the light of previous magnetic studies.     

Formation of ultracold RbCs molecules by photoassociation

The formation of ultracold metastable RbCs molecules is observed in a double species magneto-optical trap through photoassociation below the ⁸⁵Rb(5S_1/2) + ¹³³Cs(6P_3/2) dissociation limit followed by spontaneous emission. The molecules are detected by resonance enhanced two-photon ionization. Using accurate quantum chemistry calculations of the potential energy curves and transition dipole moment, we interpret the observed photoassociation process as occurring at short internuclear distance, in contrast with most previous cold atom photoassociation studies. The vibrational levels excited by photoassociation belong to the 5th 0⁺ or the 4th 0^? electronic states correlated to the Rb(5P_{1/2, 3/2}) + Cs(6S_1/2) dissociation limit. The computed vibrational distribution of the produced molecules shows that they are stabilized in deeply bound vibrational states of the lowest triplet state. We also predict that a noticeable fraction of molecules is produced in the lowest level of the electronic ground state.     

Large logarithm behaviour ofe + e − jet cross sections and event shape distributions inO(α s 2 )

We have calculated the leading and next-to-leading logarithm coefficients ofO(α _s ² )e ⁺ e ^? annihilation jet cross sections, thrust distribution and energy-energy correlation in the two-jet limit when the jet resolution and the event shape variables vanish. We have compared our results with expectations based on leading logarithm approximations used to resum the pertubative cross sections where this is possible. There is good agreement for the leading and next-to-leading coefficients of jet cross sections in the Durham scheme. Also for the thrust distribution and energy-energy correlation we find results which are consistent with the leading logarithm predictions.     

Quasi-probability distributions for arbitrary spin-j particles

Quasi-probability distribution functions f^j _WW, f^j _MM for quantum spin-j systems are derived based on the Wigner-Weyl, Margenau-Hill approaches. A probability distribution f^j _sph which is nonzero only on the surface of the sphere of radius j(j+1) is obtained by expressing the characteristic function in terms of the spherical moments. It is shown that the Wigner-Weyl distribution function turns out to be a distribution over the sphere in the classical limit.     

Improved but low-x approximated relation betweenF 2 p scaling violation and gluon momentum distribution function

We present a brief analysis on the approximate methods for the determination of gluon distribution from the scaling violation of proton structureF ₂ ^p in the low-x limit. In the leading order, a general low-x approximated relation is presented having more accuracy than the previous methods. Next-to-leading order correction is presented incorporating double-log-approximation. The proposed method is found to give good agreement with data. It may also be used to discriminate between the sets of gluon distributions in the low-x.     

Determination of rotational polarization using 1+1′ REMPI: a case study of D2 associative desorption from Cu(111)

We show, using a rate equation approach, that 1+1′ resonance-enhanced multiphoton ionization (REMPI) of D₂ can be treated as a single-photon process in the limit of high ionization laser power and that unambiguous alignment information can be obtained in this limit. We illustrate the discussion using a case study of the detection D₂ via the B₁Σ⁺_u/X¹Σ⁺_g transition and apply the methodology to obtain alignment information for D₂ (v=0, J=11) desorbed from Cu(111).     

The Inviscid Burgers Equation with Initial Value of Poissonian Type

We study the discontinuities (shocks) of the solution to the Burgers equation in the limit of vanishing viscosity (the inviscid limit) when the initial value is the opposite of the standard Poisson process p. We show that this solution is only defined for t ε (0, 1). Let T ₀ = 0 and T _n , n≧1, be the successive jumps of p. We prove that for all M > 0 the inviscid limit is characterized on the region x ε (-∞, M], t ε (0, 1) by the increasing process $N(t) = \sup \{ n \in \mathbb{N} {\text{| }}M + nt > T_n \} $ and the random set I(x) = {n ε {0,..., N(t)}‖T _n -nt≦x<T _n+1 - nt}. The positions of shocks are given in a precise manner. We give the distribution of N(t) and also the distribution of its first jump. We also prove similar results when the initial value is u _μ(y, 0) = -μp(y/μ²) + μ^-1 max(y, 0), μ ε (0, 1).     

The spectrum of multi-flavor QCD2 and the non-abelian Schwinger equation

Massless QCD₂ is dominated by classical configurations in the larre-N_f limit. We use this observation to study the theory by finding solutions to equations of motion, which are the non-abelian generalization of the Schwinger equation. We find that the spectrum consists of massive mesons with M² = e²N_f/2π, which correspond to abelian solutions. We generalize previously discovered non-abelian solutions and discuss their interpretation. We prove a no-go theorem ruling out the existence of soliton solutions. Thus the semi-classical approximation shows no baryons in the case of massless quarks, a result derived before in the strong-coupling limit only.     

Study of α-particles produced in thermal neutron induced reactions on 235U

The ²³⁵U(n_th, α) reaction and the α-particles emitted in the thermal neutron induced fission of ²³⁵U were measured using a very pure thermal neutron beam of the Grenoble high flux reactor. An upper limit of 0.66 mb was determined for the ²³⁵U(n_th, α) reaction cross section, which is lower than all the previous results. The energy distribution of the α-particles produced by the ²³⁵U(n_th, f) reaction was measured down to 7 MeV with a non-shielded surface-barrier detector telescope assembly. The measured distribution has a quasi-Gaussian shape; it reveals, however, a pronounced deviation from such a shape at lower α-energies. Several possible explanations for this deviation are discussed.     

The many levels pairing Hamiltonian for two pairs

We address the problem of two pairs of fermions living on an arbitrary number of single-particle levels of a potential well (mean field) and interacting through a pairing force in the framework of the Richardson equations. The associated solutions are classified in terms of a number v_l, which reduces to the seniority v in the limit of a large pairing strength G and yields the number of pairs not developing a collective behaviour, their energy remaining finite in the G limit. We express analytically, through the moments of the single-particle levels distribution, the collective mode energy and the two critical values G_cr⁺ and G_cr^- of the coupling which can exist on a single-particle level with no pair degeneracy. Notably G_cr⁺ and G_cr^-, when the number of single particle levels goes to infinity, merge into the critical coupling of a one-pair system G_cr (when it exists), which is not envisioned by the Richardson theory. In correspondence of G_cr, the system undergoes a transition from a mean-field- to a pairing-dominated regime. We finally explore the behaviour of the excitation energies, wave functions and pair transfer amplitudes versus G finding out that the former, for G > G_cr^-, come close to the BCS predictions, whereas the latter display a divergence at G_cr, signaling the onset of a long-range off-diagonal order in the system.     

The approximation method for calculation of the exponents of the gluon distribution, λ g , and the structure function, λ S ,at low x

We present a set of formulas using the solution of the QCD Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equation to extract of the exponents of the gluon distribution, λ _g , and structure function, λ _S , from the Regge-like behavior at low x. The exponents are found to be independent of x and to increase linearly with lnQ ² and are compared with the most data from the H1 Collaboration. We also calculated the structure function F ₂(x,Q ²) and the gluon distribution G(x,Q ²) at low x assuming the Regge-like behavior of the gluon distribution function at this limit and compared them with an NLO-QCD fit to theH1 data, two-Pomeron fit, multipole Pomeron exchange fit, and MRST (A.D. Martin, R.G. Roberts, W.J. Stirling, and R.S. Thorne), DL (A. Donnachie and P.V. Landshoff), and NLO GRV (M. Glük, E. Reya, and A. Vogt) fit results. The text was submitted by the authors in English.     

New limits on D0 (1.865) production in proton-nucleus collisions at 400 GeV/c

We present final results of a sensitive search for new particles in π^±K^? effective mass spectra observed in proton-nucleus collisions at 400 GeV/c. We establish a limit for D⁰ (1.865) production B_π⁺π^? dσ/dy < 360 nb/nucleon at y_cm^≈ ?0.4. For D?⁰ → π^?K⁺ the limit is 290 nb/nucleon.     

Hydrodynamic Limit of a B.G.K. Like Model on Domains with Boundaries and Analysis of Kinetic Boundary Conditions for Scalar Multidimensional Conservation Laws

In this paper we study the hydrodynamic limit of a B.G.K. like kinetic model on domains with boundaries via BV _loc theory. We obtain as a consequence existence results for scalar multidimensional conservation laws with kinetic boundary conditions. We require that the initial and boundary data satisfy the optimal assumptions that they all belong to L ¹∩L ^∞ with the additional regularity assumptions that the initial data are in BV _loc . We also extend our hydrodynamic limit analysis to the case of a generalized kinetic model to account for forces effects and we obtain as a consequence the existence theory for conservation laws with source terms and kinetic boundary conditions.     

M1 transition strength in the SU(3) limit of the generalized IBM-2

We generalize the SU(3) limit of the standard IBM-2 formalism of sd bosons to sdg…λ bosons, where λ denotes a boson of arbitrarily large, even angular momentum λ, and investigate the effect on the B(M1, 0₁⁺ → 1⁺) transition strength. In the SU(3) limit, all the M1 transition strength resides in a single 1⁺ state and is proportional to λ.     

A non-perturbative calculation of the infrared limit of the axial gauge gluon propagator (I)

We describe a non-perturbative study of the infrared behavior of the axial gauge gluon propagator based on the Dyson equation and Ward identities. We conclude that the propagator Δ_μν(q) displays a q^?4 singularity in the infrared limit, and that consequently the axial gauge running coupling constant g_A²)(q) displays a q^?2 singularity in the same limit. The only assumption necessary to obtain this conclusion is that the transverse part of the triple-gluon vertex function does not dominate the longitudinal part in the infrared regime.     

Superstrings in Curved Ramond-Ramond Backgrounds

We discuss the main issues related to understanding closed string spectrum in Ramond-Ramond backgrounds on the example of AdS₅ × S ⁵ and and its special limit – the maximally supersymmetric plane-wave background with constant null 5-form field strength. As we describe, in the latter case the spectrum can be found explicitly. We compare the plane-wave string spectrum with the expected form of the light-cone gauge spectrum of the AdS₅ × S ⁵ superstring and comment on the tensionless string limit.     

Polymers and g|φ|4 theory in four dimensions

We investigate the approach to the critical point and the scaling limit of a variety of models on a four-dimensional lattice, including g|φ|₄⁴ theory and the self-avoiding random walk. Our results, both theoretical and numerical, provide strong evidence for the triviality of the scaling limit and for logarithmic corrections to mean field scaling laws, as predicted by the perturbative renormalization group. We relate logarithmic corrections to scaling to the triviality of the scaling limit. Our numerical analysis is based on a novel, high-precision Monte Carlo technique.