Landau-gauge condensates from the quark propagator on the lattice

We compute the dimension-2 condensate, , and the dimension-4 mixed condensate, , from the recent quenched lattice results for the quark propagator in the Landau gauge. We fit the lattice data to the Operator Product Expansion in the "fiducial" region 1.2 GeV < Q < 3 GeV. Our result for the dynamical gluon mass at the scale of 10 GeV^2 is m_A=600-650 MeV, in agreement with independent determinations. For the mixed Landau gauge condensate of dimension-4 we get alpha_s = (-0.11 +/- 0.03) GeV^4. This value is an order of magnitude larger than the gluon condensate.Comment: 4 pages, 3 figures, references adde

Changes in the radius of a nucleon in interaction with another nucleon

We consider a two-nucleon system described by two different skyrmion models that provide attraction for the central NN potential. One of these models is based on the product ansatz and the other on dilaton coupling. Within these models we ask the question, To what degree does the nucleon swell or shrink when the internucleon separation distance is appropriate to attraction or repulsion? We find typically swelling of 3 to 4 percent for central attraction of some 40 to 50 MeV.Comment: Nine pages of plain TeX plus two uuencoded figure

QCD Sum Rules Description of Nucleons in Asymmetric Nuclear Matter

We calculate the nucleon parameters in isospin asymmetric nuclear matter using the QCD sum rules. The nucleon self-energies are expressed in terms of the in-medium values of QCD condensates. The simple approximate expressions for the self-energies are obtained in terms of these condensates. Relation between successive inclusion of the condensates and the meson-exchange picture of the nucleon interaction with medium is analyzed. The values of the self-energies and of the symmetry energy agree with those obtained by the methods of nuclear physics.Comment: 40 pages, 6 figure

Squeezed Gluon Condensate and Quark Confinement in the Global Color Model of QCD

We discuss how the presence of a squeezed gluon vacuum might lead to quark confinement in the framework of the global colour model of QCD. Using reduced phase space quantization of massive vector theory we construct a Lorentz invariant and colourless squeezed gluon condensate and show that it induces a permanent, nonlocal quark interaction (delta-function in 4-momentum space), which according to Munczek and Nemirovsky might lead to quark confinement. Our approach makes it possible to relate the strength of this effective confining quark interaction to the strength of the physical gluon condensate.Comment: 18 pages LaTeX, to appear in Int. J. Mod. Phys.

Expectation values of four-quark operators in pions

The values of four-quark operators averaged over pions are expressed through those averaged over vacuum. The specific values are obtained in the framework of the factorization assumption. For the condensates of the light quarks of the same flavour \bar q\Gamma q\bar q\Gamma q the scalar condensate is shown to be an order of magnitude larger than the other ones. The condensates containing the strange quarks \bar q q\bar s s appear to be only about twice smaller than those of the light quarks. The degeneracy of the ground state in the Nambu--Jona--Lasinio model is shown explicitly.Comment: 9 pages, no figures, typos correcte

On the Relativistic Description of the Nucleus

We discuss a relativistic theory of the atomic nuclei in the framework of the hamiltonian formalism and of the mesonic model of the nucleus. Attention is paid to the translational invariance of the theory. Our approach is centered on the concept of spectral amplitude, a function in the Dirac spinor space. We derive a Lorentz covariant equation for the latter, which requires as an input the baryon self-energy. For this we either postulate the most general Lorentz-Poincar\'e invariant expression or perform a calculation via a Bethe-Salpeter equation starting from a nucleon-nucleus interaction. We discuss the features of the nuclear spectrum obtained in the first instance. Finally the general constraints the self-energy should satisfy because of analyticity and Poincar\'e covariance are discussed

Derivation and assessment of strong coupling core-particle model from the Kerman-Klein-D\"onau-Frauendorf theory

We review briefly the fundamental equations of a semi-microscopic core-particle coupling method that makes no reference to an intrinsic system of coordinates. We then demonstrate how an intrinsic system can be introduced in the strong coupling limit so as to yield a completely equivalent formulation. It is emphasized that the conventional core-particle coupling calculation introduces a further approximation that avoids what has hitherto been the most time-consuming feature of the full theory, and that this approximation can be introduced either in the intrinsic system, the usual case, or in the laboratory system, our preference. A new algorithm is described for the full theory that largely removes the difference in complexity between the two types of calculation. Comparison of the full and approximate theories for some representative cases provides a basis for the assessment of the accuracy of the traditional approach. We find that for well-deformed nuclei, e.g. 157Gd and 157Tb, the core-coupling method and the full theory give similar results.Comment: revtex, 3 figures(postscript), submitted to Phys.Rev.

Phenylboronic Acids Probing Molecular Recognition against Class A and Class C beta-Lactamases

Worldwide dissemination of pathogens resistant to almost all available antibiotics represent a real problem preventing efficient treatment of infectious diseases. Among antimicrobial used in therapy, \u392-lactam antibiotics represent 40% thus playing a crucial role in the management of infections treatment. We report a small series of phenylboronic acids derivatives (BAs) active against class A carbapenemases KPC-2 and GES-5, and class C cephalosporinases AmpC. The inhibitory profile of our BAs against class A and C was investigated by means of molecular docking, enzyme kinetics and X-ray crystallography. We were interested in the mechanism of recognition among class A and class C to direct the design of broad serine \u392-Lactamases (SBLs) inhibitors. Molecular modeling calculations vs GES-5 and crystallographic studies vs AmpC reasoned, respectively, the ortho derivative 2 and the meta derivative 3 binding affinity. The ability of our BAs to protect \u392-lactams from BLs hydrolysis was determined in biological assays conducted against clinical strains: Fractional inhibitory concentration index (FICI) tests confirmed their ability to be synergic with \u392-lactams thus restoring susceptibility to meropenem. Considering the obtained results and the lack of cytotoxicity, our derivatives represent validated probe for the design of SBLs inhibitors

Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions

It is shown that the nuclear effects playing a relevant role in Deep Inelastic Scattering of polarized electrons by polarized $^3$He are mainly those arising from the effective proton and neutron polarizations generated by the $S'$ and $D$ waves in $^3$He. A simple and reliable equation relating the neutron, $g_1^n$, and $^3$He, $g_1^3$, spin structure functions is proposed. It is shown that the measurement of the first moment of the $^3$He structure function can provide a significant check of the Bjorken Sum Rule.Comment: 11 pages (revTeX), DFUPG 75/93; 5 (postscript) figures available upon request from the author