561 research outputs found
Domain walls between gauge theories
Noncommutative U(N) gauge theories at different N may be often thought of as
different sectors of a single theory: the U(1) theory possesses a sequence of
vacua labeled by an integer parameter N, and the theory in the vicinity of the
N-th vacuum coincides with the U(N) noncommutative gauge theory. We construct
noncommutative domain walls on fuzzy cylinder, separating vacua with different
gauge theories. These domain walls are solutions of BPS equations in gauge
theory with an extra term stabilizing the radius of the cylinder. We study
properties of the domain walls using adjoint scalar and fundamental fermion
fields as probes. We show that the regions on different sides of the wall are
not disjoint even in the low energy regime -- there are modes penetrating from
one region to the other. We find that the wall supports a chiral fermion zero
mode. Also, we study non-BPS solution representing a wall and an antiwall, and
show that this solution is unstable. We suggest that the domain walls emerge as
solutions of matrix model in large class of pp-wave backgrounds with
inhomogeneous field strength. In the M-theory language, the domain walls have
an interpretation of a stack of branes of fingerstall shape inserted into a
stack of cylindrical branes.Comment: Final version; minor corrections; to appear in Nucl.Phys.
On the energy-momentum tensor in non-commutative gauge theories
We study the properties of the energy-momentum tensor in non-commutative
gauge theories by coupling them to a weak external gravitational field. In
particular, we show that the stress tensor of such a theory coincides exactly
with that derived from a theory where a Seiberg-Witten map has been implemented
(namely, the procedure is commutative). Various other interesting features are
also discussed.Comment: 3 page
On the two-loop four-derivative quantum corrections in 4D N = 2 superconformal field theories
In \cN = 2, 4 superconformal field theories in four space-time dimensions,
the quantum corrections with four derivatives are believed to be severely
constrained by non-renormalization theorems. The strongest of these is the
conjecture formulated by Dine and Seiberg in hep-th/9705057 that such terms are
generated only at one loop. In this note, using the background field
formulation in \cN = 1 superspace, we test the Dine-Seiberg proposal by
comparing the two-loop F^4 quantum corrections in two different superconformal
theories with the same gauge group SU(N): (i) \cN = 4 SYM (i.e. \cN = 2 SYM
with a single adjoint hypermultiplet); (ii) \cN = 2 SYM with 2N hypermultiplets
in the fundamental. According to the Dine-Seiberg conjecture, these theories
should yield identical two-loop F^4 contributions from all the supergraphs
involving quantum hypermultiplets, since the pure \cN = 2 SYM and ghost sectors
are identical provided the same gauge conditions are chosen. We explicitly
evaluate the relevant two-loop supergraphs and observe that the F^4 corrections
generated have different large N behaviour in the two theories under
consideration. Our results are in conflict with the Dine-Seiberg conjecture.Comment: 26 pages, 4 EPS figures. V2: comments, appendix added. V3: a misprint
removed, discussion in the appendix of cancellation of divergences improved.
V4: typos corrected, the version to appear in NPB. V5: error in eq. (4.12)
corrected, conclusions unchange
Real-time PCR based on SYBR-Green I fluorescence: An alternative to the TaqMan assay for a relative quantification of gene rearrangements, gene amplifications and micro gene deletions
BACKGROUND:
Real-time PCR is increasingly being adopted for RNA quantification and genetic analysis. At present the most popular real-time PCR assay is based on the hybridisation of a dual-labelled probe to the PCR product, and the development of a signal by loss of fluorescence quenching as PCR degrades the probe. Though this so-called 'TaqMan' approach has proved easy to optimise in practice, the dual-labelled probes are relatively expensive.
RESULTS:
We have designed a new assay based on SYBR-Green I binding that is quick, reliable, easily optimised and compares well with the published assay. Here we demonstrate its general applicability by measuring copy number in three different genetic contexts; the quantification of a gene rearrangement (T-cell receptor excision circles (TREC) in peripheral blood mononuclear cells); the detection and quantification of GLI, MYC-C and MYC-N gene amplification in cell lines and cancer biopsies; and detection of deletions in the OPA1 gene in dominant optic atrophy.
CONCLUSION:
Our assay has important clinical applications, providing accurate diagnostic results in less time, from less biopsy material and at less cost than assays currently employed such as FISH or Southern blotting
Noncommutative Geometry, Extended W(infty) Algebra and Grassmannian Solitons in Multicomponent Quantum Hall Systems
Noncommutative geometry governs the physics of quantum Hall (QH) effects. We
introduce the Weyl ordering of the second quantized density operator to explore
the dynamics of electrons in the lowest Landau level. We analyze QH systems
made of -component electrons at the integer filling factor .
The basic algebra is the SU(N)-extended W. A specific feature is
that noncommutative geometry leads to a spontaneous development of SU(N)
quantum coherence by generating the exchange Coulomb interaction. The effective
Hamiltonian is the Grassmannian sigma model, and the dynamical field
is the Grassmannian field, describing complex Goldstone
modes and one kind of topological solitons (Grassmannian solitons).Comment: 15 pages (no figures
Breaking CPT by mixed non-commutativity
The mixed component of the non-commutative parameter \theta_{\mu M}, where
\mu = 0,1,2,3 and M is an extra dimensional index may violate four-dimensional
CPT invariance. We calculate one and two-loop induced couplings of \theta_{\mu
5} with the four-dimensional axial vector current and with the CPT odd dim=6
operators starting from five-dimensional Yukawa and U(1) theories. The
resulting bounds from clock comparison experiments place a stringent constraint
on \theta_{\mu 5}, |\theta_{\mu 5}|^{-1/2} > 5\times 10^{11} GeV. The orbifold
projection and/or localization of fermions on a 3-brane lead to CPT-conserving
physics, in which case the constraints on \theta{\mu 5} are softened.Comment: 4 pages, latex, 1 figur
Electromagnetic field angular momentum in condensed matter systems
Various electromagnetic systems can carry an angular momentum in their {\bf
E} and {\bf B} fields. The electromagnetic field angular momentum (EMAM) of
these systems can combine with the spin angular momentum to give composite
fermions or composite bosons. In this paper we examine the possiblity that an
EMAM could provide an explanation of the fractional quantum Hall effect (FQHE)
which is complimentary to the Chern-Simons explanation. We also examine a toy
model of a non-BCS superconductor (e.g. high superconductors) in terms of
an EMAM. The models presented give a common, simple picture of these two
systems in terms of an EMAM. The presence of an EMAM in these systems might be
tested through the observation of the decay modes of a charged, spin zero
unstable particle inside one of these systems.Comment: 17 pages, no figures, to be published in Phys. Rev.
Higher order contributions to the effective action of N=2 super Yang-Mills
We apply heat kernel techniques in N=1 superspace to compute the one-loop
effective action to order for chiral superfields coupled to a non-Abelian
super Yang-Mills background. The results, when combined with those of
hep-th/0210146, yield the one-loop effective action to order for any N=2
super Yang-Mills theory coupled to matter hypermultiplets.Comment: 23 pages, references adde
Entrainment of the Melatonin Rhythms in Early Postnatal Lambs and Their Mothers
Although the developing sheep can produce an appropriately timed melatonin rhythm as early as 1 week after birth, it is not known whether the lamb is able to adjust its melatonin rhythm to a change in daylength. The ability of the young lamb to entrain its pattern of melatonin secretion to a new photoperiod was determined in the present study. Eight female lambs and their mothers were raised in long days (LD 16:8) beginning 2 weeks post partum. At 7 weeks of age, the time of lights-off was advanced 8 hr, the short-day photoperiod then being LD 8:16; the time of lights-on remained unchanged. Concentrations of melatonin were measured in blood samples collected hourly on days - 1, 0, 2, 4, 6, and 13 relative to the light change. On day 0, all mothers and daughters had advanced the onset of melatonin secretion by at least 1 hr, and by day 13, 12 of 16 had completely entrained to the new photoperiod. The rate of entrainment among individuals varied; the mean rate for lambs and mothers did not differ. This study provides evidence that the melatonin-rhythm-generating system matures shortly after birth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68290/2/10.1177_074873048900400405.pd
Noncommutative Quantum Mechanics and rotating frames
We study the effect of noncommutativity of space on the physics of a quantum
interferometer located in a rotating disk in a gauge field background. To this
end, we develop a path-integral approach which allows defining an effective
action from which relevant physical quantities can be computed as in the usual
commutative case. For the specific case of a constant magnetic field, we are
able to compute, exactly, the noncommutative Lagrangian and the associated
shift on the interference pattern for any value of .Comment: 17 pages, presentation improved, references added. To appear in
Physical Review
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