8,845 research outputs found
On N=2 low energy effective actions
We propose a Wilsonian action compatible with special geometry and higher
dimension N=2 corrections, and show that the holomorphic contribution F to the
low energy effective action is independent of the infrared cutoff. We further
show that for asymptotically free SU(2) super Yang-Mills theories, the infrared
cutoff can be tuned to cancel leading corrections to F. We also classify all
local higher-dimensional contributions to the N=2 superspace effective action
that produce corrections to the Kahler potential when reduced to N=1
superspace.Comment: 9 pages, Late
The Gaugings of Maximal D=6 Supergravity
We construct the most general gaugings of the maximal D=6 supergravity. The
theory is (2,2) supersymmetric, and possesses an on-shell SO(5,5) duality
symmetry which plays a key role in determining its couplings. The field content
includes 16 vector fields that carry a chiral spinor representation of the
duality group. We utilize the embedding tensor method which determines the
appropriate combinations of these vectors that participate in gauging of a
suitable subgroup of SO(5,5). The construction also introduces the magnetic
duals of the 5 two-form potentials and 16 vector fields.Comment: 34 pages, latex, reference added, typo's corrected and minor
improvements mad
Strong Couplings of X(3872)_{J=1,2} and a New Look at J/psi Suppression in Heavy Ion Collisions
We define and compute from data the strong couplings of the X(3872) with both
of the possible quantum numbers assignments J^{PC}=1^{++},2^{-+}. We use these
to compute cross sections for J/psi resonance scattering into D Dbar*. As an
application of the results obtained we revise the calculation of the J/psi
absorption in a hot hadron gas to confront with recent RHIC observations in
Au-Au collisions.Comment: 23 pages, 18 figures, 4 table
Consistent truncation of d = 11 supergravity on AdS_4 x S^7
We study the system of equations derived twenty five years ago by B. de Wit
and the first author [Nucl. Phys. B281 (1987) 211] as conditions for the
consistent truncation of eleven-dimensional supergravity on AdS_4 x S^7 to
gauged N = 8 supergravity in four dimensions. By exploiting the E_7(7)
symmetry, we determine the most general solution to this system at each point
on the coset space E_7(7)/SU(8). We show that invariants of the general
solution are given by the fluxes in eleven-dimensional supergravity. This
allows us to both clarify the explicit non-linear ansatze for the fluxes given
previously and to fill a gap in the original proof of the consistent
truncation. These results are illustrated with several examples.Comment: 41 pages, typos corrected, published versio
A method for mechanical generation of radio frequency fields in nuclear magnetic resonance force microscopy
We present an innovative method for magnetic resonance force microscopy
(MRFM) with ultra-low dissipation, by using the higher modes of the mechanical
detector as radio frequency (rf) source. This method allows MRFM on samples
without the need to be close to an rf source. Furthermore, since rf sources
require currents that give dissipation, our method enables nuclear magnetic
resonance experiments at ultra-low temperatures. Removing the need for an
on-chip rf source is an important step towards a MRFM which can be widely used
in condensed matter physics.Comment: 7 pages, 5 figures, to be submitted to Physical Review Applie
Electric/magnetic duality for chiral gauge theories with anomaly cancellation
We show that 4D gauge theories with Green-Schwarz anomaly cancellation and
possible generalized Chern-Simons terms admit a formulation that is manifestly
covariant with respect to electric/magnetic duality transformations. This
generalizes previous work on the symplectically covariant formulation of
anomaly-free gauge theories as they typically occur in extended supergravity,
and now also includes general theories with (pseudo-)anomalous gauge
interactions as they may occur in global or local N=1 supersymmetry. This
generalization is achieved by relaxing the linear constraint on the embedding
tensor so as to allow for a symmetric 3-tensor related to electric and/or
magnetic quantum anomalies in these theories. Apart from electric and magnetic
gauge fields, the resulting Lagrangians also feature two-form fields and can
accommodate various unusual duality frames as they often appear, e.g., in
string compactifications with background fluxes.Comment: 37 pages; v2: typos corrected and 1 reference adde
Finite Sized Atomistic Simulations of Screw Dislocations
The interaction of screw dislocations with an applied stress is studied using
atomistic simulations in conjunction with a continuum treatment of the role
played by the far field boundary condition. A finite cell of atoms is used to
consider the response of dislocations to an applied stress and this introduces
an additional force on the dislocation due to the presence of the boundary.
Continuum mechanics is used to calculate the boundary force which is
subsequently accounted for in the equilibrium condition for the dislocation.
Using this formulation, the lattice resistance curve and the associated Peierls
stress are calculated for screw dislocations in several close packed metals. As
a concrete example of the boundary force method, we compute the bow out of a
pinned screw dislocation; the line-tension of the dislocation is calculated
from the results of the atomistic simulations using a variational principle
that explicitly accounts for the boundary force.Comment: LaTex, 20 pages, 11 figure
Entropy Maximization in the Presence of Higher-Curvature Interactions
Within the context of the entropic principle, we consider the entropy of
supersymmetric black holes in N=2 supergravity theories in four dimensions with
higher-curvature interactions, and we discuss its maximization at points in
moduli space at which an excess of hypermultiplets becomes massless. We find
that the gravitational coupling function F^(1) enhances the maximization at
these points in moduli space. In principle, this enhancement may be modified by
the contribution from higher F^(g)-couplings. We show that this is indeed the
case for the resolved conifold by resorting to the non-perturbative expression
for the topological free energy.Comment: 22 pages, 8 figures, AMS-LaTe
Supersymmetric Brane World Scenarios from Off-Shell Supergravity
Using N=2 off-shell supergravity in five dimensions, we supersymmetrize the
brane world scenario of Randall and Sundrum. We extend their construction to
include supersymmetric matter at the fixpoints.Comment: 15 pages, no figures, late
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