4,899 research outputs found
Remark on the open string pair production enhancement
Recent studies by one of the present authors along with his collaborators in
[1-4] show that there exist the so-called open string pair production for a
possible simplest system of two Dp branes, placed parallel at a separation and
with each carrying different electric flux, in Type II superstring theories.
Further this pair production can be greatly enhanced when a magnetic flux,
sharing no common field strength index with the electric one, is added,
implying then . Given this, one may wonder if further enhancement can
be achieved by adding more magnetic flux(es) in a similar fashion. In this
paper, we explore this possibility. It turns out that adding more such magnetic
flux diminishes rather than enhances the pair production rate. This actually
implies that the largest enhancement occurs at when the same realistic
electric and magnetic fluxes are applied for all . Curiously one of D3
branes may be our own world and if so, the enhancement gives a possible
opportunity to detect the pair production, therefore to test the underlying
string theories.Comment: 14 pages, 0 figure
On 1/4 BPS ((F, D1), (NS5, D5)) bound states of type IIB string theory
We construct two new SL(2,Z) invariant vacua of type IIB string theory which
are bound states of strings with 5-branes, written as ((F, D1),
(NS5, D5)) and preserve 1/4 of the full space-time supersymmetries. For the
first case, the strings live inside the 5-brane world-volume and in the second
case the strings are perpendicular to the 5-brane world-volume. In the first
case, naively one would expect an attractive interaction between the strings
and the 5-branes due to attractive force between F and D5 and also between D1
and NS5. We find that 1/4 BPS bound state exists only when the vacuum moduli
satisfy certain condition which is found to be consistent with the no-force
condition between the branes. No such complication arises for the second case.
The tension formulae and the various other descendant states which can be
obtained by the application of T-duality for both these bound states are
discussed.Comment: 22 pages, 1 table, minor changes and one reference added, the version
to appear in JHE
New perspective on space and time from Lorentz violation
I present a brief review on space and time in different periods of physics,
and then talk on the nature of space and time from physical arguments. I
discuss the ways to test such a new perspective on space and time through
searching for Lorentz violation in some physical processes. I also make an
introduce to a newly proposed theory of Lorentz violation from basic
considerations.Comment: 10 latex pages. Plenary talk at First LeCosPA Symposium: Towards
Ultimate Understanding of the Universe (LeCosPA2012), National Taiwan
University, Taipei, Taiwan, February 6-9, 201
The mutualistic fungus Piriformospora indica colonizes Arabidopsis roots by inducing an endoplasmic reticulum stress-triggered caspase-dependent cell death
In Arabidopsis thaliana roots, the mutualistic fungus Piriformospora indica initially colonizes living cells, which die as the colonization proceeds. We aimed to clarify the molecular basis of this colonization-associated cell death. Our cytological analyses revealed endoplasmic reticulum (ER) swelling and vacuolar collapse in invaded cells, indicative of ER stress and cell death during root colonization. Consistent with this, P. indica–colonized plants were hypersensitive to the ER stress inducer tunicamycin. By clear contrast, ER stress sensors bZIP60 and bZIP28 as well as canonical markers for the ER stress response pathway, termed the unfolded protein response (UPR), were suppressed at the same time. Arabidopsis mutants compromised in caspase 1–like activity, mediated by cell death–regulating vacuolar processing enzymes (VPEs), showed reduced colonization and decreased cell death incidence. We propose a previously unreported microbial invasion strategy during which P. indica induces ER stress but inhibits the adaptive UPR. This disturbance results in a VPE/caspase 1–like-mediated cell death, which is required for the establishment of the symbiosis. Our results suggest the presence of an at least partially conserved ER stress–induced caspase-dependent cell death pathway in plants as has been reported for metazoans
Theory for electric dipole superconductivity with an application for bilayer excitons
Exciton superfluid is a macroscopic quantum phenomenon in which large
quantities of excitons undergo the Bose-Einstein condensation. Recently,
exciton superfluid has been widely studied in various bilayer systems. However,
experimental measurements only provide indirect evidence for the existence of
exciton superfluid. In this article, by viewing the exciton in a bilayer system
as an electric dipole, we provide a general theory for the electric dipole
superconductivity, and derive the London-type and Ginzburg-Landau-type
equations for the electric dipole superconductors. By using these equations, we
discover the Meissner-type effect and the electric dipole current Josephson
effect. These effects can provide direct evidence for the formation of the
exciton superfluid state in bilayer systems and pave new ways to drive an
electric dipole current.Comment: 10 pages, 5 figures, 1 Supplementary Informatio
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