473 research outputs found
Born-Infeld Chern-Simons Theory: Hamiltonian Embedding, Duality and Bosonization
In this paper we study in detail the equivalence of the recently introduced
Born-Infeld self dual model to the Abelian Born-Infeld-Chern-Simons model in
2+1 dimensions. We first apply the improved Batalin, Fradkin and Tyutin scheme,
to embed the Born-Infeld Self dual model to a gauge system and show that the
embedded model is equivalent to Abelian Born-Infeld-Chern-Simons theory. Next,
using Buscher's duality procedure, we demonstrate this equivalence in a
covariant Lagrangian formulation and also derive the mapping between the
n-point correlators of the (dual) field strength in Born-Infeld Chern-Simons
theory and of basic field in Born-Infeld Self dual model. Using this
equivalence, the bosonization of a massive Dirac theory with a non-polynomial
Thirring type current-current coupling, to leading order in (inverse) fermion
mass is also discussed. We also re-derive it using a master Lagrangian.
Finally, the operator equivalence between the fermionic current and (dual)
field strength of Born-Infeld Chern-Simons theory is deduced at the level of
correlators and using this the current-current commutators are obtained.Comment: 27 pages, One reference added, minor changes in presentation and
typos corrected. To appear in Nucl. Phys.
Time-resolved imaging of guided wave phenomena
In the past decade, increasing demand and rapid developments in classical and quantum sciences resulted in advanced novel multipixel single photon detector arrays engineered on a single electronic chip. Silicon single photon avalanche detector (Si-SPAD) is one of the mainstream solution for low level light detection in visible and near-infrared wavelength region due to the dependable amplification of light signal. This thesis mainly focusses on three key experiments to showcase the potential applications of a single photon detector (Megaframe 32) consists of 32×32 square array Si-SPADs with picosecond timing circuits. With ≈ 50 ps timing resolution, each SPAD can perform time-correlated single photon counting independently. First, the concept of multiplexed single-mode wavelength-to-time mapping (WTM) of multimode light was investigated. The spacetime imaging capability of the Megaframe was then demonstrated by imaging the spatial modes emerging from a few-mode fibre enabling WTM of spatial modes. Finally, timeresolved discrete imaging in laser inscribed photonic lattices was demonstrated. By placing a photonic lattice in a linear cavity and re-injecting the output mode profile back to the lattice, the propagation of light was measured in quasi-real time manner. The experimental demonstrations using Megaframe will find applications in Raman spectroscopy, soliton imaging, quantum optics, and discrete waveguide optics
Aspects of Noncommutative Scalar/Tensor Duality
We study the noncommutative massless Kalb-Ramond gauge field coupled to a
dynamical U(1) gauge field in the adjoint representation together with a
compensating vector field. We derive the Seiberg-Witten map and obtain the
corresponding mapped action to first order in . The (emergent) gravity
structure found in other situations is not present here. The off-shell dual
scalar theory is derived and it does not coincide with the Seiberg-Witten
mapped scalar theory. Dispersion relations are also discussed. The p-form
generalization of the Seiberg-Witten map to order is also derived.Comment: 7 pages, typos corrected, a footnote removed and a sentence added in
the tex
On the equivalence between topologically and non-topologically massive abelian gauge theories
We analyse the equivalence between topologically massive gauge theory (TMGT)
and different formulations of non-topologically massive gauge theories (NTMGTs)
in the canonical approach. The different NTMGTs studied are St\"uckelberg
formulation of (A) a first order formulation involving one and two form fields,
(B) Proca theory, and (C) massive Kalb-Ramond theory. We first quantise these
reducible gauge systems by using the phase space extension procedure and using
it, identify the phase space variables of NTMGTs which are equivalent to the
canonical variables of TMGT and show that under this the Hamiltonian also get
mapped. Interestingly it is found that the different NTMGTs are equivalent to
different formulations of TMGTs which differ only by a total divergence term.
We also provide covariant mappings between the fields in TMGT to NTMGTs at the
level of correlation function.Comment: One reference added and a typos corrected. 15 pages, To appear in
Mod. Phys. Lett.
Metal ion and guanine nucleotide modulations of agonist interaction in G-protein-coupled serotonin<SUB>1A</SUB> receptors from bovine hippocampus
1. The serotonin type 1A (5-HT1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to GTP-binding regulatory proteins (G-proteins). We have studied the modulation of agonist binding to 5-HT1A receptors from bovine hippocampus by metal ions and guanine nucleotide. 2. Bovine hippocampal membranes containing the 5-HT1A receptor were isolated. These membranes exhibited high-affinity binding sites for the specific agonist [3H]OH-DPAT. 3. The agonist binding is inhibited by monovalent cations Na+, K+, and Li+ in a concentration-dependent manner. Divalent cations such as Ca2+, Mg2+, and Mn2+, on the other hand, show more complex behavior and induce enhancement of agonist binding up to a certain concentration. The effect of the metal ions on agonist binding is strongly modulated in the presence of GTP-γ -S, a nonhydrolyzable analogue of GTP, indicating that these receptors are coupled to G-proteins. 4. To gain further insight into the mechanisms of agonist binding to bovine hippocampal 5-HT1A receptors under these conditions, the binding affinities and binding sites have been analyzed by Scatchard analysis of saturation binding data. Our results are relevant to ongoing analyses of the overall regulation of receptor activity for G-protein-coupled seven transmembrane domain receptors
Modulation of antagonist binding to serotonin<SUB>1A</SUB> receptors from bovine hippocampus by metal ions
1. The serotonin1A(5-HT1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to G-proteins. They appear to be involved in various behavioral and cognitive functions. Although specific 5-HT1Aagonists have been discovered more than a decade back, the development of selective 5-HT1Aantagonists has been achieved only recently. 2. We have examined the modulation of the specific antagonist [3H]p-MPPF binding to 5-HT1Areceptors from bovine hippocampal membranes by monovalent and divalent metal ions. Our results show that the antagonist binding to 5-HT1Areceptors is inhibited by both monovalent and divalent cations in a concentration-dependent manner. This is accompanied by a concomitant reduction in binding affinity. 3. Our results also show that the specific antagonist p-MPPF binds to all available receptors in the bovine hippocampal membrane irrespective of their state of G-protein coupling and other serotonergic ligands such as 5-HT and OH-DPAT effectively compete with the specific antagonist [3H]p-MPPF. 4. These results are relevant to ongoing analyses of the overall modulation of ligand binding in G-protein-coupled seven transmembrane domain receptors
State-recycling and time-resolved imaging in topological photonic lattices
Photonic lattices - arrays of optical waveguides - are powerful platforms for
simulating a range of phenomena, including topological phases. While probing
dynamics is possible in these systems, by reinterpreting the propagation
direction as "time," accessing long timescales constitutes a severe
experimental challenge. Here, we overcome this limitation by placing the
photonic lattice in a cavity, which allows the optical state to evolve through
the lattice multiple times. The accompanying detection method, which exploits a
multi-pixel single-photon detector array, offers quasi-real time-resolved
measurements after each round trip. We apply the state-recycling scheme to
intriguing photonic lattices emulating Dirac fermions and Floquet topological
phases. In this new platform, we also realise a synthetic pulsed electric
field, which can be used to drive transport within photonic lattices. This work
opens a new route towards the detection of long timescale effects in engineered
photonic lattices and the realization of hybrid analogue-digital simulators.Comment: Comments are welcom
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