155 research outputs found
Matrix Sigma-models for Multi D-brane Dynamics
We describe a dynamical worldsheet origin for the Lagrangian describing the
low-energy dynamics of a system of parallel D-branes. We show how matrix-valued
collective coordinate fields for the D-branes naturally arise as couplings of a
worldsheet sigma-model, and that the quantum dynamics require that these
couplings be mutually noncommutative. We show that the low-energy effective
action for the sigma-model couplings describes the propagation of an open
string in the background of the multiple D-brane configuration, in which all
string interactions between the constituent branes are integrated out and the
genus expansion is taken into account, with a matrix-valued coupling. The
effective field theory is governed by the non-abelian Born-Infeld target space
action which leads to the standard one for D-brane field theory.Comment: 14 pages LaTeX, 1 encapsulated postscript figure; uses epsf.te
The British public's perception of the UK smart metering initiative: Threats and opportunities
Consumer acceptance of smart meters remains crucial in achieving the potential carbon emission reductions offered by advanced metering infrastructures. Given this, the present research used deliberative focus groups to examine what is needed to secure acceptance and engagement from domestic consumers with services, products and 'offers' in smarter power systems. Our findings suggest that consumers are able to identify not just threats relating to smart metering initiatives but opportunities as well. In particular, our focus group participants responded positively to the idea of an automated system that could be used to achieve energy savings in combination with time-of-use tariffs. We conclude by outlining suggestions for policy recommendations that may help consumer acceptance of smart meter enabled services be more readily achieved
Corrigendum to “The British public's perception of the UK smart metering initiative: Threats and opportunities” [Energy Policy 91 (2016) 87–97]
Towards a microscopic construction of flavour vacua from a space-time foam model
The effect on flavour oscillations of simple expanding background
space-times, motivated by some D-particle foam models, is calculated for a
toy-model of bosons with flavour degrees of freedom. The presence of D-particle
defects in the space-time, which can interact non trivially (via particle
capture) with flavoured particles in a flavour non-preserving way, generates
mixing in the effective field theory of low-energy string excitations.
Moreover, the recoil of the D-particle defect during the capture/scattering
process implies Lorentz violation, which however may be averaged to zero in
isotropic D-particle populations, but implies non-trivial effects in
correlators. Both features imply that the flavoured mixed state sees a
non-trivial flavour (Fock-space) vacuum of a type introduced earlier by Blasone
and Vitiello in a generic context of theories with mixing. We discuss the
orthogonality of the flavour vacua to the usual Fock vacua and the effect on
flavour oscillations in these backgrounds. Furthermore we analyse the equation
of state of the Flavour vacuum, and find that, for slow expansion rates induced
by D particle recoil, it is equivalent to that of a cosmological constant. Some
estimates of these novel non-perturbative contribution to the vacuum energy are
made. The contribution vanishes if the mass difference and the mixing angle of
the flavoured states vanish.Comment: 27 pages RevTex, 2 eps figures incorporate
IdleWars: an Evaluation of a Pervasive Game to Promote Sustainable Behaviour in the Workplace
A Diagramatic Analysis of Duality in Supersymmetric Gauge Theories
We introduce a diagramatic notation for supersymmetric gauge theories. The
notation is a tool for exploring duality and helps to present the field content
of more complicated models in a simple visual way. We introduce the notation
with a few examples from the literature. The power of the formalism allows us
to study new models with gauge group and their duals. Amongst these
are models which, contrary to a naive analysis, possess no conformal phase.Comment: 20 pages, LaTeX, figures include
Orientifolds, Branes, and Duality of 4D Gauge Theories
Recently, a D-brane construction in type IIA string theory was shown to yield
the electric/magnetic duality of four dimensional N=1 supersymmetric U(N_c)
gauge theories with N_f flavours of quark. We present here an extension of that
construction which yields the electric/magnetic duality for the SO(N_c) and
USp(N_c) gauge theories with N_f quarks, by adding an orientifold plane which
is consistent with the supersymmetry. Due to the intersection of the
orientifold plane with the NS-NS fivebranes already present, new features arise
which are crucial in determining the correct final structure of the dualities.Comment: 24 pages, harvmac.tex (b), 6 figures, epsf.tex (Major improvements to
figures; minor improvements to text.
Vacuum Energy and Cosmological Supersymmetry Breaking in Brane Worlds
In the context of a toy model we discuss the phenomenon of colliding
five-branes, with two of the extra space dimensions compactified on tori. In
one of the branes (hidden world) the torus is magnetised. Assuming
opposite-tension branes, we argue that the collision results eventually in a
(time-dependent) cosmological vacuum energy, whose value today is tiny, lying
comfortably within the standard bounds by setting the breaking of the
four-dimensional supersymmetry at a TeV scale. The small value of the vacuum
energy as compared with the supersymmetry-breaking scale is attributed to
transient phenomena with relaxation times of order of the Age of the Universe.
An interesting feature of the approach is the absence of a cosmic horizon,
thereby allowing for a proper definition of an S-matrix.As a result of the
string non-criticality induced at the collision,our model does not provide an
alternative to inflation, given that arguments can be given supporting the
occurence of an inflationary phase early after the collision. The physics
before the collision is not relevant to our arguments on the cosmological
constant hierarchy, which are valid for asymptotically long times after it.Comment: 11 pages LATEX, no figures, references added, discussion on inflation
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