6,270 research outputs found
Instanton operators in five-dimensional gauge theories
This article is distributed under the terms of the Creative Commons
Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in
any medium, provided the original author(s) and source are creditedN.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. OPen Aceess funded by SCOAP
Lectures on Non-BPS Dirichlet branes
A comprehensive introduction to the boundary state approach to Dirichlet
branes is given. Various examples of BPS and non-BPS Dirichlet branes are
discussed. In particular, the non-BPS states in the duality of Type IIA on K3
and the heterotic string on T4 are analysed in detail.Comment: 46 pages, 5 figures, LaTeX; lectures given at the TMR network school
on `Quantum aspects of gauge theories, supersymmetry and quantum gravity',
Torino, 26 January - 2 February 2000, and at the `Spring workshop on
Superstrings and related matters', Trieste, 27 March - 4 April 2000;
references adde
Representations of the q-deformed algebra
An algebra homomorphism from the q-deformed algebra
with generating elements , , and defining relations
, , (where
) to the extension of the
Hopf algebra is constructed. The algebra at
leads to the Lie algebra of the group ISO(2)
of motions of the Euclidean plane. The Hopf algebra is treated
as a Hopf -deformation of the universal enveloping algebra of
and is well-known in the literature. Not all irreducible representations of
can be extended to representations of the extension . Composing the homomorphism with irreducible
representations of we obtain representations of
. Not all of these representations of are
irreducible. The reducible representations of are decomposed
into irreducible components. In this way we obtain all irreducible
representations of when is not a root of unity. A part
of these representations turns into irreducible representations of the Lie
algebra iso when . Representations of the other part have no
classical analogue.Comment: 12 pages, LaTe
Zero-Mode Dynamics of String Webs
At sufficiently low energy the dynamics of a string web is dominated by zero
modes involving rigid motion of the internal strings. The dimension of the
associated moduli space equals the maximal number of internal faces in the web.
The generic web moduli space has boundaries and multiple branches, and for webs
with three or more faces the geometry is curved. Webs can also be studied in a
lift to M-theory, where a string web is replaced by a membrane wrapped on a
holomorphic curve in spacetime. In this case the moduli space is complexified
and admits a Kaehler metric.Comment: LaTeX, 17 pages, 5 eps figures; v2: references adde
Clear-cuts are temporary habitats, not matrix, for endangered grassland burnet moths (Zygaena spp.)
Burnet moths (Zygaena spp.) are day-flying Lepidoptera considered indicative of species-rich grasslands. In the present study, our aim was to clarify whether clear-cuts are habitat, supporting habitat or matrix for three species of Zygaena. We did so by sampling these species with sex pheromones on 48 clear-cuts, varying in amount of host and nectar plants, in southern Sweden. To compare the efficiency of such sampling, we also conducted transect walks on these clearcuts. Overall, host-plants on clear-cuts best explained the abundance of Zygaena spp. recorded, better than nectar-plants or connectivity with nearby grasslands. These results indicate that clear-cuts with an abundance of host plants are used as a fully functional habitat, and not a supporting habitat in the sense of only providing nectar. There is no support in these results for considering clear-cuts as an inert matrix. With about half the work-effort, pheromone traps recorded 100 times more Zygaena spp. as transect walks. The poor correspondence between observations during transects walks and pheromone trap catches suggest Zygaena spp. being difficult to monitor by transect walks. In contrast to grasslands, clear-cuts are short-term in nature requiring repeated recolonization, indicating the importance of permanent grasslands. However, clear-cuts are important temporary insect habitats due to their great acreage, and suitable management can increase the time they remain a habitat
On fluctuations of closed string tachyon solitons
We discuss fluctuations on solitons in the dilaton/graviton/tachyon system
using the low energy effective field theory approach. It is shown that closed
string solitons are free of tachyons in this approximation, regardless of the
exact shape of the tachyon potential.Comment: 13 pages, 1 figure, uses JHEP3.cl
Magnetic effects in a holographic Fermi-like liquid
We explore the magnetic properties of the Fermi-like liquid represented by
the D3-D7' system. The system exhibits interesting magnetic properties such as
ferromagnetism and an anomalous Hall effect, which are due to the Chern-Simons
term in the effective gravitational action. We investigate the spectrum of
quasi-normal modes in the presence of a magnetic field and show that the
magnetic field mitigates the instability towards a striped phase. In addition,
we find a critical magnetic field above which the zero sound mode becomes
massive.Comment: 18 pages, 15 figure
Dirichlet Branes on Orientifolds
We consider the classification of BPS and non-BPS D-branes in orientifold
models. In particular we construct all stable BPS and non-BPS D-branes in the
Gimon-Polchinski (GP) and Dabholkar-Park-Blum-Zaffaroni (DPBZ) orientifolds and
determine their stability regions in moduli space as well as decay products. We
find several kinds of integrally and torsion charged non-BPS D-branes. Certain
of these are found to have projective representations of the orientifold
GSO group on the Chan-Paton factors. It is found that the GP
orientifold is not described by equivariant orthogonal K-theory as may have
been at first expected. Instead a twisted version of this K-theory is expected
to be relevant.Comment: 33 pages, LaTeX, 5 figures. v2 typos corrected, references included,
(4,s)-branes re-examine
Exactly stable non-BPS spinors in heterotic string theory on tori
Considering SO(32) heterotic string theory compactified on a torus of
dimension 4 and less, stability of non-supersymmetric states is studied. A
non-supersymmetric state with robust stability is constructed, and its exact
stability is proven in a large region of moduli space against all the possible
decay mechanisms allowed by charge conservation. Using various T-duality
transform matrices, we translate various selection rules about conserved
charges into simpler problems resembling partition and parity of integers. For
heterotic string on T^4, we give a complete list of BPS atoms with elementary
excitations, and we study BPS and non-BPS molecules with various binding
energies. Using string-string duality, the results are interpreted in terms of
Dirichlet-branes in type IIA string theory compactified on an orbifold limit of
a K3 surface.Comment: 47 pages, 14 figures, LaTe
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