6,689 research outputs found
First Sound in Holographic Superfluids at Zero Temperature
Within the context of AdS/CFT, the gravity dual of an s-wave superfluid is
given by scalar QED on an asymptotically AdS spacetime. While this conclusion
is vastly supported by numerical arguments, here we provide an analytical proof
that this is indeed the case. Working at zero temperature, we explicitly find
the quadratic action for the superfluid phonon at the boundary in an arbitrary
number of dimensions and for an arbitrary scalar field potential, recovering
the known dispersion relation for conformal first sound.Comment: 14 pages. Extended discussions in sections 3 and
A Structural Analysis of Field/Circuit Coupled Problems Based on a Generalised Circuit Element
In some applications there arises the need of a spatially distributed
description of a physical quantity inside a device coupled to a circuit. Then,
the in-space discretised system of partial differential equations is coupled to
the system of equations describing the circuit (Modified Nodal Analysis) which
yields a system of Differential Algebraic Equations (DAEs). This paper deals
with the differential index analysis of such coupled systems. For that, a new
generalised inductance-like element is defined. The index of the DAEs obtained
from a circuit containing such an element is then related to the topological
characteristics of the circuit's underlying graph. Field/circuit coupling is
performed when circuits are simulated containing elements described by
Maxwell's equations. The index of such systems with two different types of
magnetoquasistatic formulations (A* and T-) is then deduced by showing
that the spatial discretisations in both cases lead to an inductance-like
element
Ridge jump process in Iceland
Eastward ridge jumps bring the volcanic zones of Iceland back to the centre of the hotspot in response to the absolute westward drift of the Mid-Atlantic Ridge. Mantellic pulses triggers these ridge jumps. One of them is occurring in Southern Iceland, whereas the exact conditions of the last ridge jump in Northern Iceland remain controversial. The diachronous evolution of these two parts of Iceland may be related to the asymmetric plume-ridge interaction when comparing Northern and Southern Iceland
Reduced Order Modelling for the Simulation of Quenches in Superconducting Magnets
This contributions discusses the simulation of magnetothermal effects in
superconducting magnets as used in particle accelerators. An iterative coupling
scheme using reduced order models between a magnetothermal partial differential
model and an electrical lumped-element circuit is demonstrated. The
multiphysics, multirate and multiscale problem requires a consistent
formulation and framework to tackle the challenging transient effects occurring
at both system and device level
Classifying Galileon -form theories
We provide a complete classification of all abelian gauge invariant -form
theories with equations of motion depending only on the second derivative of
the field---the -form analogues of the Galileon scalar field theory. We
construct explicitly the nontrivial actions that exist for spacetime dimension
, but our methods are general enough and can be extended to arbitrary
. We uncover in particular a new -form Galileon cubic theory in
dimensions. As a by-product we give a simple proof of the fact that the
equations of motion depend on the -form gauge fields only through their
field strengths, and show this explicitly for the recently discovered -form
Galileon quartic theory.Comment: 17 pages; v2: references adde
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