9,975 research outputs found
Nuclear fission: The "onset of dissipation" from a microscopic point of view
Semi-analytical expressions are suggested for the temperature dependence of
those combinations of transport coefficients which govern the fission process.
This is based on experience with numerical calculations within the linear
response approach and the locally harmonic approximation. A reduced version of
the latter is seen to comply with Kramers' simplified picture of fission. It is
argued that for variable inertia his formula has to be generalized, as already
required by the need that for overdamped motion the inertia must not appear at
all. This situation may already occur above T=2 MeV, where the rate is
determined by the Smoluchowski equation. Consequently, comparison with
experimental results do not give information on the effective damping rate, as
often claimed, but on a special combination of local stiffnesses and the
friction coefficient calculated at the barrier.Comment: 31 pages, LaTex, 9 postscript figures; final, more concise version,
accepted for publication in PRC, with new arguments about the T-dependence of
the inertia; e-mail: [email protected]
Exact Superpotentials, Theories with Flavor and Confining Vacua
In this paper we study some interesting properties of the effective
superpotential of N=1 supersymmetric gauge theories with fundamental matter,
with the help of the Dijkgraaf--Vafa proposal connecting supersymmetric gauge
theories with matrix models.
We find that the effective superpotential for theories with N_f fundamental
flavors can be calculated in terms of quantities computed in the pure (N_f=0)
gauge theory. Using this property we compute in a remarkably simple way the
exact effective superpotential of N=1 supersymmetric theories with fundamental
matter and gauge group SU(N_c), at the point in the moduli space where a
maximal number of monopoles become massless (confining vacua). We extend the
analysis to a generic point of the moduli space, and show how to compute the
effective superpotential in this general case.Comment: 16 pages, no figure
Symplectic Quantization of Open Strings and Noncommutativity in Branes
We show how to translate boundary conditions into constraints in the
symplectic quantization method by an appropriate choice of generalized
variables. This way the symplectic quantization of an open string attached to a
brane in the presence of an antisymmetric background field reproduces the non
commutativity of the brane coordinates.Comment: We included a comparison with previous results obtained from Dirac
quantization, emphasizing the fact that in the symplectic case the boundary
conditions, that lead to the non commutativity, show up from the direct
application of the standard method. Version to appear in Phys. Rev.
Cobicistat as a Potential Booster of Ponatinib and Dasatinib Exposure in a CML Patient:A Case Study
The authors present a case of a 57-year-old patient with chronic myeloid leukemia who was treated with ponatinib and subsequently treated with dasatinib. The patient showed a major molecular response; however, the BCR-ABL1 signal increased with low ponatinib and dasatinib trough concentrations. Cobicistat was used as a pharmacokinetic booster to increase ponatinib and dasatinib exposure, as opposed to increasing the dose. However, ponatinib exposure was not sufficiently increased by cobicistat. The peak dasatinib concentration was successfully increased with cobicistat treatment. Dasatinib and cobicistat cotreatment induced a response in BCR-ABL1 PCR signal, was well tolerated, and led to a substantial reduction in drug costs.</p
Low Energy Analyzing Powers in Pion-Proton Elastic Scattering
Analyzing powers of pion-proton elastic scattering have been measured at PSI
with the Low Energy Pion Spectrometer LEPS as well as a novel polarized
scintillator target. Angular distributions between 40 and 120 deg (c.m.) were
taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic
energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering.
These new measurements constitute a substantial extension of the polarization
data base at low energies. Predictions from phase shift analyses are compared
with the experimental results, and deviations are observed at low energies.Comment: 15 pages, 4 figure
AdS_7/CFT_6, Gauss-Bonnet Gravity, and Viscosity Bound
We study the relation between the causality and the positivity of energy
bounds in Gauss-Bonnet gravity in AdS_7 background and find a precise
agreement. Requiring the group velocity of metastable states to be bounded by
the speed of light places a bound on the value of Gauss-Bonnet coupling. To
find the positivity of energy constraints we compute the parameters which
determine the angular distribution of the energy flux in terms of three
independent coefficients specifying the three-point function of the
stress-energy tensor. We then relate the latter to the Weyl anomaly of the
six-dimensional CFT and compute the anomaly holographically. The resulting
upper bound on the Gauss-Bonnet coupling coincides with that from causality and
results in a new bound on viscosity/entropy ratio.Comment: 21 page, harvmac; v2: reference adde
Parton picture for the strongly coupled SYM plasma
Deep inelastic scattering off the strongly coupled N=4 supersymmetric
Yang-Mills plasma at finite temperature can be computed within the AdS/CFT
correspondence, with results which are suggestive of a parton picture for the
plasma. Via successive branchings, essentially all partons cascade down to very
small values of the longitudinal momentum fraction x and to transverse momenta
smaller than the saturation momentum Q_s\sim T/x. This scale Q_s controls the
plasma interactions with a hard probe, in particular, the jet energy loss and
its transverse momentum broadening.Comment: 4 pages, Talk given at Quark Matter 2008: 20th International
Conference on Ultra-Relativistic Nucleus Nucleus Collisions (QM 2008),
Jaipur, India, 4-10 Feb 200
Adding Fundamental Matter to ``Chiral Rings and Anomalies in Supersymmetric Gauge Theory''
We consider a supersymmetric U(N) gauge theory with matter fields in the
adjoint, fundamental and anti-fundamental representations. As in the framework
which was put forward by Dijkgraaf and Vafa, this theory can be described by a
matrix model. We analyze this theory along the lines of [F. Cachazo, M.
Douglas, N.S. and E. Witten, ``Chiral Rings and Anomalies in Supersymmetric
Gauge Theory'' hep-th/0211170] and show the equivalence of the gauge theory and
the matrix model. In particular, the anomaly equations in the gauge theory is
identified with the loop equations in the matrix model.Comment: 14 page
Reflecting magnons from D7 and D5 branes
We obtain the reflection matrices for the scattering of elementary magnons
from certain open boundaries, corresponding to open strings ending on D7 and D5
branes in . In each case we consider two possible orientations
for the vacuum state. We show that symmetry arguments are sufficient to
determine the reflection matrices up to at most two unknown functions. The D7
reflection matrices obey the boundary Yang Baxter-Equation. This is automatic
for one vacuum orientation, and requires a natural choice of ratio between two
unknowns for the other. In contrast, the D5 reflection matrices do not obey the
boundary Yang Baxter-Equation. In both cases we show consistency with the
existent weak and strong coupling results.Comment: 32 pages, 1 figure; v2: added references and minor changes; v3: error
in boundary Yang-Baxter equation for D5 reflection matrix note
Phases of N=1 Supersymmetric SO/Sp Gauge Theories via Matrix Model
We extend the results of Cachazo, Seiberg and Witten to N=1 supersymmetric
gauge theories with gauge groups SO(2N), SO(2N+1) and Sp(2N). By taking the
superpotential which is an arbitrary polynomial of adjoint matter \Phi as a
small perturbation of N=2 gauge theories, we examine the singular points
preserving N=1 supersymmetry in the moduli space where mutually local monopoles
become massless. We derive the matrix model complex curve for the whole range
of the degree of perturbed superpotential. Then we determine a generalized
Konishi anomaly equation implying the orientifold contribution. We turn to the
multiplication map and the confinement index K and describe both Coulomb branch
and confining branch. In particular, we construct a multiplication map from
SO(2N+1) to SO(2KN-K+2) where K is an even integer as well as a multiplication
map from SO(2N) to SO(2KN-2K+2) (K is a positive integer), a map from SO(2N+1)
to SO(2KN-K+2) (K is an odd integer) and a map from Sp(2N) to Sp(2KN+2K-2).
Finally we analyze some examples which show some duality: the same moduli space
has two different semiclassical limits corresponding to distinct gauge groups.Comment: 55pp; two paragraphs in page 19 added to clarify the relation between
confinement index and multiplication map index, refs added and to appear in
JHEP; Konishi anomaly equations corrected and some comments on the
degenerated cases for SO(7) and SO(8) adde
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