1,495 research outputs found
Mitigating smart card fault injection with link-time code rewriting: a feasibility study
We present a feasibility study to protect smart card software against fault-injection attacks by means of binary code rewriting. We implemented a range of protection techniques in a link-time rewriter and evaluate and discuss the obtained coverage, the associated overhead and engineering effort, as well as its practical usability
Absorption cross section in warped AdS_3 black hole revisited
We investigate the absorption cross section for minimal-coupled scalars in
the warped AdS_3 black hole. According to our calculation, the cross section
reduces to the horizon area in the low energy limit as usually expected in
contrast to what was previously found. We also calculate the greybody factor
and find that the effective temperatures for the two chiral CFT's are
consistent with that derived from the quasinormal modes. Observing the
conjectured warped AdS/CFT correspondence, we suspect that a specific sector of
the CFT operators with the desired conformal dimension could be responsible for
the peculiar thermal behaviour of the warped AdS_3 black hole.Comment: 16+1 pages, typos corrected, references and footnotes adde
Experimental constraints on the parameter space of the next-to-minimal supersymmetric standard model at LEP 2
We search for the neutral Higgs sector of the next-to-minimal supersymmetric
standard model at LEP 2. At the tree level any experimental constraints on
cannot be set by the Higgs search at LEP 2 with = 175
GeV, whereas at LEP 2 with = 192 GeV can be set by an
experimental constraint. Furthermore the tree level parameter space of the
model can be completely explored by the Higgs search at LEP 2 with =
205 GeV. Radiative corrections both to the neutral Higgs boson masses and to
the relevant couplings for the scalar Higgs productions give large
contributions to the production cross sections of the scalar Higgs bosons at
the tree level. The tree level situation at LEP 2 with = 192 GeV as
well as with = 205 GeV can be drastically changed by these effects.
We expect that a small region of the 1-loop level parameter space of the model
via the scalar Higgs production can be explored by the Higgs search at LEP 2.Comment: 14 pages (3 figures are included
Role of a SER immune suppressor in immune surveillance
A potent immunosuppressor factor, known as SER (suppressive E-receptor factor) has been identified in the body fluids of cancer patients. SER has been proven to be immunochemically analogous to the fetal form of haptoglobin. In this paper, we examine the role of SER immune suppressor in the immune surveillance mechanism of the host, using an affinity-purified SER. As shown in this study, SER, at μg/ml concentrations, inhibits the T-cell proliferation induced with either monoclonal or polyclonal T-cell activators in vitro in human, and also inhibits the primary antibody response to T-dependent antigens in vivo in mice. Likewise, SER also inhibits the immunoglobulin synthesis of human B lymphocytes induced by a B-cell mitogen, pokeweed mitogen, in the presence of a tumour promotor, phorbol myristate acetate (PMA). In contrast to the T-dependent antibody response in vivo in mice or T-dependent mitogen response in vitro in human, SER does not interfere with the T-independent antibody responses to DNP-Ficoll or TNP-LPS in mice. SER also interferes with the natural killer cell function of human peripheral blood mononuclear cells. Although SER inhibits the phagocytic functions of human peripheral neutrophils, it requires at least 10-20 times the concentration of SER present in normal human plasma. Since this concentration of SER is attainable in the sera of solid tumour-bearing patients, highly elevated levels of SER could predispose the patients to microbial infections as well. This study demonstrates that purified SER manifests multi-faceted down-regulatory effects on the defence mechanism of hosts, thereby it could compromise the patients' cell-mediated immunity in vivo
Chiral field theories from conifolds
We discuss the geometric engineering and large n transition for an N=1 U(n)
chiral gauge theory with one adjoint, one conjugate symmetric, one
antisymmetric and eight fundamental chiral multiplets. Our IIB realization
involves an orientifold of a non-compact Calabi-Yau A_2 fibration, together
with D5-branes wrapping the exceptional curves of its resolution as well as the
orientifold fixed locus. We give a detailed discussion of this background and
of its relation to the Hanany-Witten realization of the same theory. In
particular, we argue that the T-duality relating the two constructions maps the
Z_2 orientifold of the Hanany-Witten realization into a Z_4 orientifold in type
IIB. We also discuss the related engineering of theories with SO/Sp gauge
groups and symmetric or antisymmetric matter.Comment: 34 pages, 8 figures, v2: References added, minor correction
Critical behavior of the planar magnet model in three dimensions
We use a hybrid Monte Carlo algorithm in which a single-cluster update is
combined with the over-relaxation and Metropolis spin re-orientation algorithm.
Periodic boundary conditions were applied in all directions. We have calculated
the fourth-order cumulant in finite size lattices using the single-histogram
re-weighting method. Using finite-size scaling theory, we obtained the critical
temperature which is very different from that of the usual XY model. At the
critical temperature, we calculated the susceptibility and the magnetization on
lattices of size up to . Using finite-size scaling theory we accurately
determine the critical exponents of the model and find that =0.670(7),
=1.9696(37), and =0.515(2). Thus, we conclude that the
model belongs to the same universality class with the XY model, as expected.Comment: 11 pages, 5 figure
Holomorphic matrix models
This is a study of holomorphic matrix models, the matrix models which
underlie the conjecture of Dijkgraaf and Vafa. I first give a systematic
description of the holomorphic one-matrix model. After discussing its
convergence sectors, I show that certain puzzles related to its perturbative
expansion admit a simple resolution in the holomorphic set-up. Constructing a
`complex' microcanonical ensemble, I check that the basic requirements of the
conjecture (in particular, the special geometry relations involving chemical
potentials) hold in the absence of the hermicity constraint. I also show that
planar solutions of the holomorphic model probe the entire moduli space of the
associated algebraic curve. Finally, I give a brief discussion of holomorphic
models, focusing on the example of the quiver, for which I extract
explicitly the relevant Riemann surface. In this case, use of the holomorphic
model is crucial, since the Hermitian approach and its attending regularization
would lead to a singular algebraic curve, thus contradicting the requirements
of the conjecture. In particular, I show how an appropriate regularization of
the holomorphic model produces the desired smooth Riemann surface in the
limit when the regulator is removed, and that this limit can be described as a
statistical ensemble of `reduced' holomorphic models.Comment: 45 pages, reference adde
Relative error prediction via kernel regression smoothers
In this article, we introduce and study local constant and local linear nonparametric regression estimators when it is appropriate to assess performance in terms of mean squared relative error of prediction. We give asymptotic results for both boundary and non-boundary cases. These are special cases of more general asymptotic results that we provide concerning the estimation of the ratio of conditional expectations of two functions of the response variable. We also provide a good bandwidth selection method for the estimators. Examples of application, limited simulation results and discussion of related problems and approaches are also given
A Simple Shell Model for Quantum Dots in a Tilted Magnetic Field
A model for quantum dots is proposed, in which the motion of a few electrons
in a three-dimensional harmonic oscillator potential under the influence of a
homogeneous magnetic field of arbitrary direction is studied. The spectrum and
the wave functions are obtained by solving the classical problem. The ground
state of the Fermi-system is obtained by minimizing the total energy with
regard to the confining frequencies. From this a dependence of the equilibrium
shape of the quantum dot on the electron number, the magnetic field parameters
and the slab thickness is found.Comment: 15 pages (Latex), 3 epsi figures, to appear in PhysRev B, 55 Nr. 20
(1997
Chiral field theories, Konishi anomalies and matrix models
We study a chiral N=1, U(N) field theory in the context of the Dijkgraaf-Vafa
correspondence. Our model contains one adjoint, one conjugate symmetric and one
antisymmetric chiral multiplet, as well as eight fundamentals. We compute the
generalized Konishi anomalies and compare the chiral ring relations they induce
with the loop equations of the (intrinsically holomorphic) matrix model defined
by the tree-level superpotential of the field theory. Surprisingly, we find
that the matrix model is well-defined only if the number of flavors equals two!
Despite this mismatch, we show that the 1/N expansion of the loop equations
agrees with the generalized Konishi constraints. This indicates that the matrix
model - gauge theory correspondence should generally be modified when applied
to theories with net chirality. We also show that this chiral theory produces
the same gaugino superpotential as a nonchiral SO(N) model with a single
symmetric multiplet and a polynomial superpotential.Comment: 43 page
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