6,959 research outputs found
The Schwinger SU(3) construction - I: Multiplicity problem and relation to induced representations
The Schwinger oscillator operator representation of SU(3) is analysed with
particular reference to the problem of multiplicity of irreducible
representations. It is shown that with the use of an unitary
representation commuting with the SU(3) representation, the infinity of
occurrences of each SU(3) irreducible representation can be handled in complete
detail. A natural `generating representation' for SU(3), containing each
irreducible representation exactly once, is identified within a subspace of the
Schwinger construction; and this is shown to be equivalent to an induced
representation of SU(3).Comment: Latex, 25 page
The cohomology of superspace, pure spinors and invariant integrals
The superform construction of supersymmetric invariants, which consists of
integrating the top component of a closed superform over spacetime, is
reviewed. The cohomological methods necessary for the analysis of closed
superforms are discussed and some further theoretical developments presented.
The method is applied to higher-order corrections in heterotic string theory up
to \a'^3. Some partial results on and are also given.Comment: 24 pages. Minor changes; added reference
Characteristics of long-duration inhibitory postsynaptic potentials in rat neocortical neurons in vitro
1. The characteristics of long-duration inhibitory postsynaptic potentials (l-IPSPs) which are evoked in rat frontal neocortical neurons by local electrical stimulation were investigated with intracellular recordings from anin vitro slice preparation.
2. Stimulation with suprathreshold intensities evoked l-IPSPs with typical durations of 600–900 msec at resting membrane potential. Conductance increases of 15–60% were measured at the peak amplitude of l-IPSPs (150–250 msec poststimulus).
3. The duration of the conductance increases during l-IPSPs displayed a significant voltage dependence, decreasing as the membrance potential was depolarized and increasing with hyperpolarization.
4. The reversal potential of l-IPSPs is significantly altered by reductions in the extracellular potassium concentration. Therefore it is concluded that l-IPSPs in rat neocortical neurons are generated by the activation of a potassium conductance.
5. l-IPSPs exhibit stimulation fatigue. Stimulation with a frequency of 1 Hz produces a complete fatigue of the conductance increases during l-IPSPs after approximately 20 consecutive stimuli. Recovery from this fatigue requires minutes.
6. l-IPSPs are not blocked by bicuculline but are blocked by baclofen
Kappa-symmetry for coincident D-branes
A kappa-symmetric action for coincident D-branes is presented. It is valid in
the approximation that the additional fermionic variables, used to incorporate
the non-abelian degrees of freedom, are treated classically. The action is
written as a Bernstein-Leites integral on the supermanifold obtained from the
bosonic worldvolume by adjoining the extra fermions. The integrand is a very
simple extension of the usual Green-Schwarz action for a single brane; all
symmetries, except for kappa, are manifest, and the proof of kappa-symmetry is
very similar to the abelian case.Comment: 18 pages. References adde
Spatial incoherence of solar granulation: a global analysis using BiSON 2B data
A poor understanding of the impact of convective turbulence in the outer
layers of the Sun and Sun-like stars challenges the advance towards an improved
understanding of their internal structure and dynamics. Assessing and
calibrating these effects is therefore of great importance. Here we study the
spatial coherence of granulation noise and oscillation modes in the Sun, with
the aim of exploiting any incoherence to beat-down observed granulation noise,
hence improving the detection of low-frequency p-modes. Using data from the
BiSON 2B instrument, we assess the coherence between different atmospheric
heights and between different surface regions. We find that granulation noise
from the different atmospheric heights probed is largely incoherent; frequency
regions dominated by oscillations are almost fully coherent. We find a
randomised phase difference for the granulation noise, and a near zero
difference for the evanescent oscillations. A reduction of the incoherent
granulation noise is shown by application of the cross-spectrum.Comment: 8 pages, 7 figures, MNRAS in pres
Orthosymplectically invariant functions in superspace
The notion of spherically symmetric superfunctions as functions invariant
under the orthosymplectic group is introduced. This leads to dimensional
reduction theorems for differentiation and integration in superspace. These
spherically symmetric functions can be used to solve orthosymplectically
invariant Schroedinger equations in superspace, such as the (an)harmonic
oscillator or the Kepler problem. Finally the obtained machinery is used to
prove the Funk-Hecke theorem and Bochner's relations in superspace.Comment: J. Math. Phy
BPS Solitons in M5-Brane Worldvolume Theory with Constant Three-Form Field
We study BPS solutions for a self-dual string and a neutral string in
M5-brane worldvolume theory with constant three-form field. We further
generalize such solitons to superpose with a calibrated surface. We also study
a traveling wave on a calibrated surface in the constant three-form field
background.Comment: 12 pages, LaTeX, minor correction, added referenc
Towards a manifestly supersymmetric action for 11-dimensional supergravity
We investigate the possibility of writing a manifestly supersymmetric action
for 11-dimensional supergravity. The construction involves an explicit relation
between the fields in the super-vielbein and the super-3-form, and uses
non-minimal pure spinors. A simple cubic interaction term for a single scalar
superfield is found.Comment: 22 pp., plain tex. v2: references adde
Free Differential Algebras and Pure Spinor Action in IIB Superstring Sigma Models
In this paper we extend to the case of IIB superstring sigma models the
method proposed in hep-th/10023500 to derive the pure spinor approach for type
IIA sigma models. In particular, starting from the (Free) Differential Algebra
and superspace parametrization of type IIB supergravity, extended to include
the BRST differential and all the ghosts, we derive the BRST transformations of
fields and ghosts as well as the standard pure spinor constraints for the
ghosts related to supersymmetry. Moreover, using the method first
proposed by us, we derive the pure spinor action for type IIB superstrings in
curved supergravity backgrounds (on shell), in full agreement with the action
first obtained by Berkovits and Howe.Comment: 24 page
Ten-Dimensional Super-Twistors and Super-Yang-Mills
Four-dimensional super-twistors provide a compact covariant description of
on-shell N=4 d=4 super-Yang-Mills. In this paper, ten-dimensional
super-twistors are introduced which similarly provide a compact covariant
description of on-shell d=10 super-Yang-Mills. The super-twistor variables are
Z=(lambda^alpha, mu_alpha, Gamma^m) where lambda^alpha and mu_alpha are
constrained bosonic d=10 spinors and Gamma^m is a constrained fermionic d=10
vector. The Penrose map relates the twistor superfield Phi(Z) with the d=10
super-Yang-Mills vertex operator lambda^alpha A_alpha(x,theta) which appears in
the pure spinor formalism of the superstring, and the cubic super-Yang-Mills
amplitude is proportional to the super-twistor integral \int dZ Phi_1 Phi_2
Phi_3.Comment: 14 pages harvmac, added short clarificatio
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