1,406 research outputs found
Fungal Respiratory Infections in Cystic Fibrosis (CF): Recent Progress and Future Research Agenda
International audienc
Supersymmetric AdS(4) compactifications of IIA supergravity
We derive necessary and sufficient conditions for N=1 compactifications of
(massive) IIA supergravity to AdS(4) in the language of SU(3) structures. We
find new solutions characterized by constant dilaton and nonzero fluxes for all
form fields. All fluxes are given in terms of the geometrical data of the
internal compact space. The latter is constrained to belong to a special class
of half-flat manifolds.Comment: 24 pages, references adde
Non-BPS Dyons and Branes in the Dirac-Born-Infeld Theory
Non-BPS dyon solutions to D3-brane actions are constructed when one or more
scalar fields describing transverse fluctuations of the brane, are considered.
The picture emerging from such non-BPS configurations is analysed, in
particular the response of the D-brane-string system to small perturbations.Comment: 16 pages, 4 figures, Revtex fil
On operad structures of moduli spaces and string theory
Recent algebraic structures of string theory, including homotopy Lie
algebras, gravity algebras and Batalin-Vilkovisky algebras, are deduced from
the topology of the moduli spaces of punctured Riemann spheres. The principal
reason for these structures to appear is as simple as the following. A
conformal field theory is an algebra over the operad of punctured Riemann
surfaces, this operad gives rise to certain standard operads governing the
three kinds of algebras, and that yields the structures of such algebras on the
(physical) state space naturally.Comment: 33 pages (An elaboration of minimal area metrics and new references
are added
Electronic Structure and Heavy Fermion Behavior in LiV_2O_4
First principles density functional calculations of the electronic and
magnetic properties of spinel-structure LiVO have been performed
using the full potential linearized augmented planewave method. The
calculations show that the electronic structure near the Fermi energy consists
of a manifold of 12 bands derived from V states, weakly hybridized
with O p states. While the total width of this active manifold is approximately
2 eV, it may be roughly decomposed into two groups: high velocity bands and
flatter bands, although these mix in density functional calculations. The flat
bands, which are the more atomic-like lead to a high density of states and
magnetic instability of local moment character. The value of the on-site
exchange energy is sensitive to the exact exchange correlation parameterization
used in the calculations, but is much larger than the interaction between
neighboring spins, reflecting the weak coupling of the magnetic system with the
high velocity bands. A scenario for the observed heavy fermion behavior is
discussed in which conduction electrons in the dispersive bands are weakly
scattered by local moments associated with strongly correlated electrons in the
heavy bands.This is analogous to that in conventional Kondo type heavy
fermions, but is unusual in that both the local moments and conduction
electrons come from the same d-manifold.Comment: 6 Revtex pages, Postscript figs embedded. Revision: figure 4 replaced
with a better version, showing the band character explicitel
Theory of ac electrokinetic behavior of spheroidal cell suspensions with an intrinsic dispersion
The dielectric dispersion, dielectrophoretic (DEP) and electrorotational (ER)
spectra of spheroidal biological cell suspensions with an intrinsic dispersion
in the constituent dielectric constants are investigated. By means of the
spectral representation method, we express analytically the characteristic
frequencies and dispersion strengths both for the effective dielectric constant
and the Clausius-Mossotti factor (CMF). We identify four and six characteristic
frequencies for the effective dielectric spectra and CMF respectively, all of
them being dependent on the depolarization factor (or the cell shape). The
analytical results allow us to examine the effects of the cell shape, the
dispersion strength and the intrinsic frequency on the dielectric dispersion,
DEP and ER spectra. Furthermore, we include the local-field effects due to the
mutual interactions between cells in a dense suspension, and study the
dependence of co-field or anti-field dispersion peaks on the volume fractions.Comment: accepted by Phys. Rev.
N=1,2 supersymmetric vacua of IIA supergravity and SU(2) structures
We consider backgrounds of (massive) IIA supergravity of the form of a warped
product , where is a six-dimensional compact
manifold and is or a four-dimensional Minkowski space. We
analyse conditions for and supersymmetry on
manifolds of SU(2) structure. We prove the absence of solutions in certain
cases.Comment: 24 pages; v2: reference adde
Three-dimensional N=8 conformal supergravity and its coupling to BLG M2-branes
This paper is concerned with the problem of coupling the N=8 superconformal
Bagger-Lambert-Gustavsson (BLG) theory to N=8 conformal supergravity in three
dimensions. We start by constructing the on-shell N=8 conformal supergravity in
three dimensions consisting of a Chern-Simons type term for each of the gauge
fields: the spin connection, the SO(8) R-symmetry gauge field and the spin 3/2
Rarita-Schwinger (gravitino) field. We then proceed to couple this theory to
the BLG theory. The final theory should have the same physical content, i.e.,
degrees of freedom, as the ordinary BLG theory. We discuss briefly the
properties of this "topologically gauged" BLG theory and why this theory may be
useful.Comment: 20 pages, v2: references and comments added, presentation in section
3.2 extended. v3: misprints and a sign error corrected, version published in
JHE
Multiple Intersections of D-branes and M-branes
We give a classification of all multiple intersections of D-branes in ten
dimensions and M-branes in eleven dimensions that corresponds to threshold BPS
bound states. The residual supersymmetry of these composite branes is
determined. By dimensional reduction composite p-branes in lower dimensions can
be constructed. We emphasize in dimensions D greater or equal than two, those
solutions which involve a single scalar and depend on a single harmonic
function. For these extremal branes we obtain the strength of the coupling
between the scalar and the gauge field. In particular we give a D-brane and
M-brane interpretation of extreme p-branes in two, three and four dimensions.Comment: 28 pages, LaTeX, 4 figures, corrections in table 1 and figure
Supergravity Solutions for BI Dyons
We construct partially localized supergravity counterpart solutions to the
1/2 supersymmetric non-threshold and the 1/4 supersymmetric threshold bound
state BI dyons in the D3-brane Dirac-Born-Infeld theory. Such supergravity
solutions have all the parameters of the BI dyons. By applying the IIA/IIB
T-duality transformations to these supergravity solutions, we obtain the
supergravity counterpart solutions to 1/2 and 1/4 supersymmetric BIons carrying
electric and magnetic charges of the worldvolume U(1) gauge field in the
Dirac-Born-Infeld theory in other dimensions.Comment: 17 pages, REVTeX, revised version to appear in Phys. Rev.
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