6,992 research outputs found
The Loop Group of E8 and Targets for Spacetime
The dimensional reduction of the E8 gauge theory in eleven dimensions leads
to a loop bundle in ten dimensional type IA string theory. We show that the
restriction to the Neveu-Schwarz sector leads naturally to a sigma model with
target space E8 with the ten-dimensional spacetime as the source. The
corresponding bundle has a structure group the group of based loops, whose
classifying space we study. We explore some consequences of this proposal such
as possible Lagrangians and existence of flat connections.Comment: 17 pages, main section improved, change in title, reference and
acknowledgement adde
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
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
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
DDF Construction and D-Brane Boundary States in Pure Spinor Formalism
Open string boundary conditions for non-BPS D-branes in type II string
theories discussed in hep-th/0505157 give rise to two sectors with integer (R
sector) and half-integer (NS sector) modes for the combined fermionic matter
and bosonic ghost variables in pure spinor formalism. Exploiting the manifest
supersymmetry of the formalism we explicitly construct the DDF (Del Giudice, Di
Vecchia, Fubini) states in both the sectors which are in one-to-one
correspondence with the states in light-cone Green-Schwarz formalism. We also
give a proof of validity of this construction. A similar construction in the
closed string sector enables us to define a physical Hilbert space in pure
spinor formalism which is used to project the covariant boundary states of both
the BPS and non-BPS instantonic D-branes. These projected boundary states take
exactly the same form as those found in light-cone Green-Schwarz formalism and
are suitable for computing the cylinder diagram with manifest open-closed
duality.Comment: 37 pages, typos corrected, some organisational changes mad
Moduli Space Dimensions of Multi-Pronged Strings
The numbers of bosonic and fermionic zero modes of multi-pronged strings are
counted in super-Yang-Mills theory and compared with those of the
IIB string theory. We obtain a nice agreement for the fermionic zero modes,
while our result for the bosonic zero modes differs from that obtained in the
IIB string theory. The possible origin of the discrepancy is discussedComment: 15 pages, 2 figure
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
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