1,978 research outputs found
On Heavy-Quark Free Energies, Entropies, Polyakov Loop, and AdS/QCD
In this paper we explore some of the features of a heavy quark-antiquark pair
at finite temperature using a five-dimensional framework nowadays known as
AdS/QCD. We shall show that the resulting behavior is consistent with our
qualitative expectations of thermal gauge theory. Some of the results are in
good agreement with the lattice data that provides additional evidence for the
validity of the proposed model.Comment: 15 pages, 10 figures; v2: comments added, misprints correcte
Tuning a Polar Molecule for Selective Cytoplasmic Delivery by a pH (Low) Insertion Peptide
Drug molecules are typically hydrophobic and small in order to traverse membranes to reach cytoplasmic targets, but we have discovered that more polar molecules can be delivered across membranes using water-soluble, moderately hydrophobic membrane peptides of the pHLIP (pH low insertion peptide) family. Delivery of polar cargo molecules could expand the chemical landscape for pharmacological agents that have useful activity but are too polar by normal drug criteria. The spontaneous insertion and folding of the pHLIP peptide across a lipid bilayer seeks a free energy minimum, and insertion is accompanied by a release of energy that can be used to translocate cell-impermeable cargo molecules. In this study, we report our first attempt to tune the hydrophobicity of a polar cargo, phallacidin, in a systematic manner. We present the design, synthesis, and characterization of three phallacidin cargoes, where the hydrophobicity of the cargo was tuned by the attachment of diamines of various lengths of hydrophobic chains. The phallacidin cargoes were conjugated to pHLIP and shown to selectively inhibit the proliferation of cancer cells in a concentration-dependent manner at low pH
Shot noise in mesoscopic systems
This is a review of shot noise, the time-dependent fluctuations in the
electrical current due to the discreteness of the electron charge, in small
conductors. The shot-noise power can be smaller than that of a Poisson process
as a result of correlations in the electron transmission imposed by the Pauli
principle. This suppression takes on simple universal values in a symmetric
double-barrier junction (suppression factor 1/2), a disordered metal (factor
1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect
on this shot-noise suppression, while thermalization of the electrons due to
electron-electron scattering increases the shot noise slightly. Sub-Poissonian
shot noise has been observed experimentally. So far unobserved phenomena
involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev
reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic
Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn,
NATO ASI Series E (Kluwer Academic Publishing, Dordrecht
Three-loop HTL gluon thermodynamics at intermediate coupling
We calculate the thermodynamic functions of pure-glue QCD to three-loop order
using the hard-thermal-loop perturbation theory (HTLpt) reorganization of
finite temperature quantum field theory. We show that at three-loop order
hard-thermal-loop perturbation theory is compatible with lattice results for
the pressure, energy density, and entropy down to temperatures .
Our results suggest that HTLpt provides a systematic framework that can used to
calculate static and dynamic quantities for temperatures relevant at LHC.Comment: 24 pages, 13 figs. 2nd version: improved discussion and fixing typos.
Published in JHE
Polynomial super-gl(n) algebras
We introduce a class of finite dimensional nonlinear superalgebras providing gradings of . Odd generators close by anticommutation on polynomials (of
degree ) in the generators. Specifically, we investigate `type I'
super- algebras, having odd generators transforming in a single
irreducible representation of together with its contragredient.
Admissible structure constants are discussed in terms of available
couplings, and various special cases and candidate superalgebras are identified
and exemplified via concrete oscillator constructions. For the case of the
-dimensional defining representation, with odd generators , and even generators , , a three
parameter family of quadratic super- algebras (deformations of
) is defined. In general, additional covariant Serre-type conditions
are imposed, in order that the Jacobi identities be fulfilled. For these
quadratic super- algebras, the construction of Kac modules, and
conditions for atypicality, are briefly considered. Applications in quantum
field theory, including Hamiltonian lattice QCD and space-time supersymmetry,
are discussed.Comment: 31 pages, LaTeX, including minor corrections to equation (3) and
reference [60
Improved high-temperature expansion and critical equation of state of three-dimensional Ising-like systems
High-temperature series are computed for a generalized Ising model with
arbitrary potential. Two specific ``improved'' potentials (suppressing leading
scaling corrections) are selected by Monte Carlo computation. Critical
exponents are extracted from high-temperature series specialized to improved
potentials, achieving high accuracy; our best estimates are:
, , , ,
. By the same technique, the coefficients of the small-field
expansion for the effective potential (Helmholtz free energy) are computed.
These results are applied to the construction of parametric representations of
the critical equation of state. A systematic approximation scheme, based on a
global stationarity condition, is introduced (the lowest-order approximation
reproduces the linear parametric model). This scheme is used for an accurate
determination of universal ratios of amplitudes. A comparison with other
theoretical and experimental determinations of universal quantities is
presented.Comment: 65 pages, 1 figure, revtex. New Monte Carlo data by Hasenbusch
enabled us to improve the determination of the critical exponents and of the
equation of state. The discussion of several topics was improved and the
bibliography was update
Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays
Bose-Einstein correlations of both neutral and like-sign charged pion pairs
are measured in a sample of 2 million hadronic Z decays collected with the L3
detector at LEP. The analysis is performed in the four-momentum difference
range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be
smaller than that of charged pions. This result is in qualitative agreement
with the string fragmentation model
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
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