48 research outputs found
Three-dimensional structure of Serratia marcescens nuclease at 1.7 Å resolution and mechanism of its action
AbstractThe three-dimensional crystal structure of Serratia marcescens (Sm) nuclease has been refined at 1.7 Å resolution to the R-factor of 17.3% and R-free of 22.2%. The final model consists of 3678 non-hydrogen atoms and 443 water molecules. The analysis of the secondary and the tertiary structures of the Sm nuclease suggests a topology which reveals essential inner symmetry in all the three layers forming the monomer. We propose the plausible mechanism of its action based on a concerted participation of the catalytically important amino acid residues of the enzyme active site
Star product and the general Leigh-Strassler deformation
We extend the definition of the star product introduced by Lunin and
Maldacena to study marginal deformations of N=4 SYM. The essential difference
from the latter is that instead of considering U(1)xU(1) non-R-symmetry, with
charges in a corresponding diagonal matrix, we consider two Z_3-symmetries
followed by an SU(3) transformation, with resulting off-diagonal elements. From
this procedure we obtain a more general Leigh-Strassler deformation, including
cubic terms with the same index, for specific values of the coupling constants.
We argue that the conformal property of N=4 SYM is preserved, in both beta-
(one-parameter) and gamma_{i}-deformed (three-parameters) theories, since the
deformation for each amplitude can be extracted in a prefactor. We also
conclude that the obtained amplitudes should follow the iterative structure of
MHV amplitudes found by Bern, Dixon and Smirnov.Comment: 21 pages, no figures, JHEP3, v2: references added, v3: appendix A
added, v4: clarification in section 3.
Instanton test of non-supersymmetric deformations of the AdS_5 x S^5
We consider instanton effects in a non-supersymmetric gauge theory obtained
by marginal deformations of the N=4 SYM. This gauge theory is expected to be
dual to type IIB string theory on the AdS_5 times deformed-S^5 background. From
an instanton calculation in the deformed gauge theory we extract the prediction
for the dilaton-axion field \tau in dual string theory. In the limit of small
deformations where the supergravity regime is valid, our instanton result
reproduces the expression for \tau of the supergravity solution found by
Frolov.Comment: 15 page
THE OPTIMIZATION OF THE PARTS MADE OF TITANIUM ALLOYS MANUFACTURE TECHNOLOGICAL PROCESS FOR THE NICKEL AND CHROME COVERS ADHESION ENSURING
The works on the chrome cover adhesion on parts “piston with a rod” made of BT3-1, BT-22 alloys ensuring have been carried out based on the examination of residual stresses in a parts surface layer after grinding and harden¬ing by surface plastic deforming
THE ENSURING OF CHASSIS PISTON RODS AND CYLINDERS CHROME COVERING HERMETICITY USING CONSECUTIVE DIAMOND BURNISHING
The technology of chassis parts diamond burnishing has been worked out that ensure the hermeticity of chrome covering without rechroming and repeated diamond burnishing
Yangians in Deformed Super Yang-Mills Theories
We discuss the integrability structure of deformed, four-dimensional N=4
super Yang-Mills theories using Yangians. We employ a recent procedure by
Beisert and Roiban that generalizes the beta deformation of Lunin and Maldacena
to produce N=1 superconformal gauge theories, which have the superalgebra
SU(2,2|1)xU(1)xU(1). The deformed theories, including those with the more
general twist, were shown to have retained their integrable structure. Here we
examine the Yangian algebra of these deformed theories. In a five field
subsector, we compute the two cases of SU(2)xU(1)xU(1)xU(1) and
SU(2|1)xU(1)xU(1) as residual symmetries of SU(2,2|1)xU(1)xU(1). We compute a
twisted coproduct for these theories, and show that only for the residual
symmetry do we retain the standard coproduct. The twisted coproduct thus
provides a method for symmetry breaking. However, the full Yangian structure of
SU(2|3) is manifest in our subsector, albeit with twisted coproducts, and
provides for the integrability of the theory.Comment: 17 page
Real versus complex beta-deformation of the N=4 planar super Yang-Mills theory
This is a sequel of our paper hep-th/0606125 in which we have studied the
{\cal N}=1 SU(N) SYM theory obtained as a marginal deformation of the {\cal
N}=4 theory, with a complex deformation parameter \beta and in the planar
limit. There we have addressed the issue of conformal invariance imposing the
theory to be finite and we have found that finiteness requires reality of the
deformation parameter \beta. In this paper we relax the finiteness request and
look for a theory that in the planar limit has vanishing beta functions. We
perform explicit calculations up to five loop order: we find that the
conditions of beta function vanishing can be achieved with a complex
deformation parameter, but the theory is not finite and the result depends on
the arbitrary choice of the subtraction procedure. Therefore, while the
finiteness condition leads to a scheme independent result, so that the
conformal invariant theory with a real deformation is physically well defined,
the condition of vanishing beta function leads to a result which is scheme
dependent and therefore of unclear significance. In order to show that these
findings are not an artefact of dimensional regularization, we confirm our
results within the differential renormalization approach.Comment: 18 pages, 7 figures; v2: one reference added; v3: JHEP published
versio
On the perturbative chiral ring for marginally deformed N=4 SYM theories
For \cal{N}=1 SU(N) SYM theories obtained as marginal deformations of the
\cal{N}=4 parent theory we study perturbatively some sectors of the chiral ring
in the weak coupling regime and for finite N. By exploiting the relation
between the definition of chiral ring and the effective superpotential we
develop a procedure which allows us to easily determine protected chiral
operators up to n loops once the superpotential has been computed up to (n-1)
order. In particular, for the Lunin-Maldacena beta-deformed theory we determine
the quantum structure of a large class of operators up to three loops. We
extend our procedure to more general Leigh-Strassler deformations whose chiral
ring is not fully understood yet and determine the weight-two and weight-three
sectors up to two loops. We use our results to infer general properties of the
chiral ring.Comment: LaTex, 40 pages, 4 figures, uses JHEP3; v2: minor correction
Integrable twists in AdS/CFT
A class of marginal deformations of four-dimensional N=4 super Yang-Mills
theory has been found to correspond to a set of smooth, multiparameter
deformations of the S^5 target subspace in the holographic dual on AdS_5 x S^5.
We present here an analogous set of deformations that act on global toroidal
isometries in the AdS_5 subspace. Remarkably, certain sectors of the string
theory remain classically integrable in this larger class of so-called
gamma-deformed AdS_5 x S^5 backgrounds. Relying on studies of deformed
su(2)_gamma models, we formulate a local sl(2)_gamma Lax representation that
admits a classical, thermodynamic Bethe equation (based on the Riemann-Hilbert
interpretation of Bethe's ansatz) encoding the spectrum in the deformed AdS_5
geometry. This result is extended to a set of discretized, asymptotic Bethe
equations for the twisted string theory. Near-pp-wave energy spectra within
sl(2)_gamma and su(2)_gamma sectors provide a useful and stringent test of such
equations, demonstrating the reliability of this technology in a wider class of
string backgrounds. In addition, we study a twisted Hubbard model that yields
certain predictions of the dual beta-deformed gauge theory.Comment: v2: references and clarifications added, 46 page
Giants On Deformed Backgrounds
We study giant graviton probes in the framework of the three--parameter
deformation of the AdS_5 x S^5 background. We examine both the case when the
brane expands in the deformed part of the geometry and the case when it blows
up into AdS. Performing a detailed analysis of small fluctuations around the
giants, the configurations turn out to be stable. Our results hold even for the
supersymmetric Lunin-Maldacena deformation.Comment: LaTex, 28 pages, uses JHEP3; v2: minor corrections, references added;
v3: final version accepted for publication in JHE