5,667 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
The nonperturbative closed string tachyon vacuum to high level
We compute the action of closed bosonic string field theory at quartic order
with fields up to level ten. After level four, the value of the potential at
the minimum starts oscillating around a nonzero negative value, in contrast
with the proposition made in [5]. We try a different truncation scheme in which
the value of the potential converges faster with the level. By extrapolating
these values, we are able to give a rather precise value for the depth of the
potential.Comment: 24 pages. v2: typos corrected, clarified extrapolation in scheme B,
and added extrapolated tachyon and dilaton vev's at the end of Section
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
D-brane interactions in type IIB plane-wave background
The cylinder diagrams that determine the static interactions between pairs of
Dp-branes in the type IIB plane wave background are evaluated. The resulting
expressions are elegant generalizations of the flat-space formulae that depend
on the value of the Ramond-Ramond flux of the background in a non-trivial
manner. The closed-string and open-string descriptions consistently transform
into each other under a modular transformation only when each of the
interacting D-branes separately preserves half the supersymmetries. These
results are derived for configurations of euclidean signature
D(p+1)-instantons but also generalize to lorentzian signature Dp-branes.Comment: 24 pages, Normalisation of boundary states correcte
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
Striped instability of a holographic Fermi-like liquid
We consider a holographic description of a system of strongly-coupled
fermions in 2+1 dimensions based on a D7-brane probe in the background of
D3-branes. The black hole embedding represents a Fermi-like liquid. We study
the excitations of the Fermi liquid system. Above a critical density which
depends on the temperature, the system becomes unstable towards an
inhomogeneous modulated phase which is similar to a charge density and spin
wave state. The essence of this instability can be effectively described by a
Maxwell-axion theory with a background electric field. We also consider the
fate of zero sound at non-zero temperature.Comment: 16 pages, 9 figures; v2: added discussion and one figure. Typos
correcte
Non-commutativity and Open Strings Dynamics in Melvin Universes
We compute the Moyal phase factor for open strings ending on D3-branes
wrapping a NSNS Melvin universe in a decoupling limit explicitly using world
sheet formalism in cylindrical coordinates.Comment: 12 pages, 1 figure, references adde
Momentum modes of M5-branes in a 2d space
We study M5 branes by considering the selfdual strings parallel to a plane.
With the internal oscillation frozen, each selfdual string gives a 5d SYM
field. All selfdual strings together give a 6d field with 5 scalars, 3 gauge
degrees of freedom and 8 fermionic degrees of freedom in adjoint representation
of U(N). Selfdual strings with the same orientation have the SYM-type
interaction. For selfdual strings with the different orientations, which could
also be taken as the unparallel momentum modes of the 6d field on that plane or
the (p,q) (r,s) strings on D3 with (p,q)\neq (r,s), the [i,j]+[j,k]\rightarrow
[i,k] relation is not valid, so the coupling cannot be written in terms of the
standard N \times N matrix multiplication. 3-string junction, which is the
bound state of the unparallel [i,j] [j,k] selfdual strings, may play a role
here.Comment: 37 pages, 5 figures, to appear in JHEP; v2: reference adde
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
Utilization of photon orbital angular momentum in the low-frequency radio domain
We show numerically that vector antenna arrays can generate radio beams which
exhibit spin and orbital angular momentum characteristics similar to those of
helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies (< 1
GHz), digital techniques can be used to coherently measure the instantaneous,
local field vectors and to manipulate them in software. This opens up for new
types of experiments that go beyond those currently possible to perform in
optics, for information-rich radio physics applications such as radio
astronomy, and for novel wireless communication concepts.Comment: 4 pages, 5 figures. Changed title, identical to the paper published
in PR
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