598 research outputs found
A New Supersymmetric Compactification of Chiral IIB Supergravity
We present a new compactification of chiral, N=2 ten-dimensional supergravity
down to five dimensions and show that it corresponds to the N=2 supersymmetric
critical point of five-dimensional, N=8 gauged supergravity found in [KPW].
This solution presented here is of particular significance because it involves
non-zero tensor gauge fields and, via the AdS/CFT correspondence, is dual to
the non-trivial N=1 supersymmetric fixed point of N=4 Yang-Mills theory.Comment: 14 pages, references added, some typos correcte
Quantum phase transition in an atomic Bose gas with a Feshbach resonance
We show that in an atomic Bose gas near a Feshbach resonance a quantum phase
transition occurs between a phase with only a molecular Bose-Einstein
condensate and a phase with both an atomic and a molecular Bose-Einstein
condensate. We show that the transition is characterized by an Ising order
parameter. We also determine the phase diagram of the gas as a function of
magnetic field and temperature: the quantum critical point extends into a line
of finite temperature Ising transitions.Comment: 4 pages, 2 figure
New Vacua of Gauged N=8 Supergravity
We analyze a particular SU(2) invariant sector of the scalar manifold of
gauged N=8 supergravity in five dimensions, and find all the critical points of
the potential within this sector. The critical points give rise to Anti-de
Sitter vacua, and preserve at least an SU(2) gauge symmetry. Consistent
truncation implies that these solutions correspond to Anti-de Sitter
compactifications of IIB supergravity, and hence to possible near-horizon
geometries of 3-branes. Thus we find new conformal phases of softly broken N=4
Yang--Mills theory. One of the critical points preserves N=2 supersymmetry in
the bulk and is therefore completely stable, and corresponds to an N=1
superconformal fixed point of the Yang--Mills theory. The corresponding
renormalization group flow from the N=4 point has c_{IR}/c_{UV} = 27/32. We
also discuss the ten-dimensional geometries corresponding to these critical
points.Comment: 14 pages, 1 table, harvma
Operator Formulation of q-Deformed Dual String Model
We present an operator formulation of the q-deformed dual string model
amplitude using an infinite set of q-harmonic oscillators. The formalism
attains the crossing symmetry and factorization and allows to express the
general n-point function as a factorized product of vertices and propagators.Comment: 6pages, Late
Spectrum of D=6, N=4b Supergravity on AdS_3 x S^3
The complete spectrum of D=6, N=4b supergravity with n tensor multiplets
compactified on AdS_3 x S^3 is determined. The D=6 theory obtained from the K_3
compactification of Type IIB string requires that n=21, but we let n be
arbitrary. The superalgebra that underlies the symmetry of the resulting
supergravity theory in AdS_3 coupled to matter is SU(1,1|2)_L x SU(1,1|2)_R.
The theory also has an unbroken global SO(4)_R x SO(n) symmetry inherited from
D=6. The spectrum of states arranges itself into a tower of spin-2
supermultiplets, a tower of spin-1, SO(n) singlet supermultiplets, a tower of
spin-1 supermultiplets in the vector representation of SO(n) and a special
spin-1/2 supermultiplet also in the vector representation of SO(n). The SU(2)_L
x SU(2)_R Yang-Mills states reside in the second level of the spin-2 tower and
the lowest level of the spin-1, SO(n) singlet tower and the associated field
theory exhibits interesting properties.Comment: 37 pages, latex, 5 tables and 3 figures, typos corrected, a reference
adde
Hearing capacities and otolith size in two ophidiiform species (<i>Ophidion rochei</i> and <i>Carapus acus</i>)
Numerous studies have highlighted the diversity of fish inner ear morphology. However, the function of the shape, size and orientation of the different structures remains poorly understood. The saccule (otolithic endorgan) is considered to be the principal hearing organ in fishes and it has been hypothesized that sagitta (saccular otolith) shape and size affect hearing capacities: large sagittae are thought to increase sensitivity. The sagittae of many ophidiids and carapids occupy a large volume inside the neurocranium. Hence they are a good structure with which to test the size hypothesis. The main aim of this study was to investigate hearing capacities and inner ear morphology in two ophidiiform species: Ophidion rochei and Carapus acus. We used a multidisciplinary approach that combines dissections, µCT-scan examinations and auditory evoked potential techniques. Carapus acus and O. rochei sagittae have similar maximal diameters; both species have larger otoliths than many non-ophidiiform species, especially compared with the intra-neurocranium volume. Both species are sensitive to sounds up to 2100 Hz. Relative to the skull, O. rochei has smaller sagittae than the carapid, but better hearing capacities from 300 to 900 Hz and similar sensitivities at 150 Hz and from 1200 to 2100 Hz. Results show that hearing capacities of a fish species cannot be predicted only based on sagitta size. Larger otoliths (in size relative to the skull) may have evolved mainly for performing vestibular functions in fishes, especially those species that need to execute precise and complex movements
Kaehler forms and cosmological solutions in type II supergravities
We consider cosmological solutions to type II supergravity theories where the
spacetime is split into a FRW universe and a K\"ahler space, which may be taken
to be Calabi-Yau. The various 2-forms present in the theories are taken to be
proportional to the K\"ahler form associated to the K\"ahler space.Comment: 6 pages, LaTeX2
Cosmological Solutions of Horava-Witten Theory
We discuss simple cosmological solutions of Horava-Witten theory describing
the strongly coupled heterotic string. At energies below the grand-unified
scale, the effective theory is five- not four-dimensional, where the additional
coordinate parameterizes a S^1/Z_2 orbifold. Furthermore, it admits no
homogeneous solutions. Rather, the vacuum state, appropriate for a reduction to
four-dimensional supersymmetric models, is a BPS domain wall. Relevant
cosmological solutions are those associated with this BPS state. In particular,
such solutions must be inhomogeneous, depending on the orbifold coordinate as
well as on time. We present two examples of this new type of cosmological
solution, obtained by separation of variables rather that by exchange of time
and radius coordinate applied to a brane solution, as in previous work. The
first example represents the analog of a rolling radii solution with the radii
specifying the geometry of the domain wall. This is generalized in the second
example to include a nontrivial ``Ramond-Ramond'' scalar.Comment: 21 pages, Latex 2e with amsmath, minor addition
Modelling of a Two-Signal SFQ Detection Scheme for the Readout of Superconducting Nanowire Single Photon Detectors
We present a two-signal single flux quantum (SFQ) detection scheme for the purpose of reading out two pixels of a superconducting nanowire single photon detector (SNSPD). The circuit is based on a coincidence buffer element which is able to output a signal when both of its input lines are triggered. The circuit model for the SNSPD element is simulated in SPICE and optimized to match the experimental SNSPD response data. The two-signal detection scheme is simulated using JSIM which allows for the simulation of Josephson junction elements in a circuit. We demonstrate a model of the two-signal circuit operating with two simulated SNSPD pixel inputs and investigate the response of the scheme when a phase shift is applied to one of the inputs. The scheme shows potential as a useful coincidence detector of single photons. We also present preliminary experimental results of nanobridge-based Josephson junctions to be used in the realization of the coincidence detector circuit. Evidence of the nanobridges exhibiting Josephson behavior (SQUID modulation) are presented
- …