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101.
Spatial noncommutativity is similar and can even be related to the non- Abelian nature of multiple D-branes. But they have
so far seemed independent of each other. Reflecting this decoupling, the algebra of matrix valued fields on noncommutative
space is thought to be the simple tensor product of constant matrix algebra and the Moyal-Weyl deformation. We propose scenarios
in which the two become intertwined and inseparable. Therefore the usual separation of ordinary or noncommutative space from
the internal discrete space responsible for non-Abelian symmetry is really the exceptional case of an unified structure. We
call it non-Abelian geometry. This general structure emerges when multiple D-branes are configured suitably in a flat but varying B field background, or in the presence of non-Abelian gauge field background. It can also occur in connection with Taub-NUT
geometry. We compute the deformed product of matrix valued functions using the lattice string quantum mechanical model developed
earlier. The result is a new type of associative algebra defining non-Abelian geometry. A possible supergravity dual is also
discussed.
Received: 13 December 2000 / Accepted: 24 October 2002 Published online: 24 January 2003
Communicated by R. H. Dijkgraaf 相似文献
102.
103.
It is shown that for pulsed optical parametric oscillators there is an optimum pumppulse duration at which the threshold fluence is a minimum. The dependence of the threshold fluence on pump laser pulse duration is found to be substantial for lossy narrowband optical parametric oscillators. The pulse energy requirement for the pump laser may be substantially lowered by operating it at a pulse duration close to the optimum. 相似文献
104.
Continued fractions w.r.t. a specified class of numbers is considered. The invariant measures of the corresponding transformations are identified connecting the continued fractions with geodesics on the upper half plane. A problem of convergence in distribution of sums of the coefficients of the continued fraction is also considered. 相似文献
105.
P. N. Bajaj K. G. Manohar B. M. Suri K. Dasgupta R. Talukdar P. K. Chakraborti P. R. K. Rao 《Applied physics. B, Lasers and optics》1988,47(1):55-59
Using two pulsed tunable dye lasers, a two colour multiphoton ionization process has been utilised to explore the higher energy levels of uranium. One hundred and thirty eight new UI levels have been observed in the 37540–38420 cm–1 region. J assignments of these levels have been suggested on the basis of their excitation from intermediate levels with known and contiguous J values. In eight cases the J assignments are unique. 相似文献
106.
Mrinal Dasgupta 《Pramana》2004,62(3):675-678
The recent discovery and resummation of a class of single logarithmic effects (non-global logs), has a significant impact
on several QCD observables ranging from the classic Sterman-Weinberg jet definition to currently studied event shapes and
rapidity gap observables. The discovery of the above effects overturns, for example, the common wisdom that hadronic energy
flow in limited inter-jet regions is dictatedprimarily by the colour flow of the underlying hard partonic subprocess. We discuss some features of non-global logs and the rapid
progress being made in estimating and controlling such corrections. 相似文献
107.
P. Sen S. Chakraborty Subinay Dasgupta B. K. Chakrabarti 《Zeitschrift für Physik B Condensed Matter》1992,88(3):333-338
We have estimated numerically the phase diagram of a one dimensional spin 1/2 quantum Ising model with competing nearest and next nearest neighbour interactions in presence of a transverse field. The method essentially is to diagonalise exactly the Hamiltonian for finite (10 spins) open chains and calculate the spin-spin correlations from the ground state eigenvector. The results obtained confirm the transition between ferromagnetic and paramagnetic phases for <0.5 and between antiphase and paramagnetic phase for >0.5. ( is the ratio of next nearest and nearest neighbour interactions.) The results perhaps indicate furthermore that (i) there is a disorder line passing through =0.5; (ii) the zero point quantum fluctuations destroy the order near =0.5 as the transverse field is switched on; and (iii) there is probably also a floating phase with slowly decayling correlation near the order-disorder phase boundary for >0.5. 相似文献
108.
A fluorometric technique based on a liquid drop excited from its interior by an optical fiber is described for the measurement of low concentrations of atmospheric hydrogen sulfide (H(2)S). A drop of alkaline fluorescein mercuric acetate (FMA) solution is suspended in a flowing air sample stream and serves as a renewable sensor. An optical fiber contained within the conduit that forms the drop, brings in the excitation beam; the fluorescence emission is measured by an inexpensive photodiode positioned close to the drop. As H(2)S in the sample is collected by the alkaline drop, it reacts rapidly with FMA resulting in a significant decrease in fluorescence intensity, proportional to the concentration of H(2)S sampled. The chemistry of this uniquely selective reaction has been well established for many years; the present technique permits a simple fast inexpensive near real-time measurement with very little reagent consumption. Even without prolonged sampling/preconcentration steps, limits of detection (LODs) in the double digit ppbv range is readily attainable. 相似文献
109.
D. Chakravarti R. N. Chakravarti L. A. Cohen B. Dasgupta S. Datta H. K. Miller 《Tetrahedron》1961,16(1-4):224-250
On the basis of a critical study of the ultra-violet and the infra-red absorption spectra of arborine, dihydroarborine, 1,2-dimethylquinazol-4-one, 2-ethyl-1-methylquinazol-4-one, 2,3-dihydro-1,2-dimethylquinazol-4-one and 2,3-dihydro-2-ethyl-1-methylquinazol-4-one, it has been shown that arborine is 2-benzyl-1-methylquinazol-4-one and not the tautomeric form, 2-benzylidene-1-methylquinazol-4-one. This has been confirmed on the basis of the nuclear magnetic resonance spectrum of arborine. Incidentally, it has been shown that 'glycosine' of Chatterjee and Ghosh Majumdar is not a new alkaloid and this name should be deleted from the literature. 相似文献
110.
The experimental system involves the permeative preconcentration of CO(2) from an acidified sample through a tubular silicone rubber membrane into a suitable receptor. Procedures for measuring the CO(2) collected in the receptor by the absorbance change of an acid-base indicator incorporated in the receptor or by the conductance change of the receptor are compared. Previous theoretical considerations of the photometric system are augmented for numerical modeling and the theoretical behavior of the conductometric system is considered in detail. Experimental data generally conform to theoretical expectations. Based on either reproducibility or sensitivity, the conductometric measurement method using a solution of 1-10mM tris(hydroxymethylamino)methane as receptor is recommended. The interference from sulfite or sulfide can be eliminated by adding acidic permanganate to the sample; considerably more involved arrangements are necessary to eliminate interferences from cyanide. 相似文献