Off-shell nilpotent (anti-)BRST symmetries for a free particle system on a toric geometry: superfield formalism

We derive the off-shell nilpotent as well as absolutely anticommuting (anti-)BRST symmetry transformations, within the framework of superfield approach to BRST formalism, for a free particle system constrained to move on a torus. We also construct the most appropriate gauge-fixed Lagrangian which respects the (anti-)BRST symmetry transformations.Comment: LaTeX file v3: 15 pages, single column, no figures, typo fixed in Eq. (18

Novel discrete symmetries in the general N = 2 supersymmetric quantum mechanical model

In addition to the usual supersymmetric (SUSY) continuous symmetry transformations for the general N = 2 SUSY quantum mechanical model, we show the existence of a set of novel discrete symmetry transformations for the Lagrangian of the above SUSY quantum mechanical model. Out of all these discrete symmetry transformations, a unique discrete transformation corresponds to the Hodge duality operation of differential geometry and the above SUSY continuous symmetry transformations (and their anticommutator) provide the physical realizations of the de Rham cohomological operators of differential geometry. Thus, we provide a concrete proof of our earlier conjecture that any arbitrary N= 2 SUSY quantum mechanical model is an example of a Hodge theory where the cohomological operators find their physical realizations in the language of symmetry transformations of this theory. Possible physical implications of our present study are pointed out, too.Comment: LaTeX file, 9 pages, EPJC format, To appear in EPJ

Further experimental results on the structure and acoustics of turbulent jet flames

The structure of open turbulent jet flames is experimentally studied in the context of their noise emission characteristics. The differences between premixed and (co-flow) non-premixed flames are explored. Recent experiments repeated in an anechoic chamber complement earlier results obtained in a hard-walled bay. The reactants (methane and enriched air) are burned in the premixed, or non-premixed, mode after a length of pipe flow (ℓ/D> 150). The thick-walled tubes anchor the flames to the tip at all of the velocities employed (maximum velocity, well over 300 ft/sec), thus eliminating uncertainties associated with external flameholders. The time-averaged appearance of the flames is obtained with still photographs (1160 sec). The detailed structures are revealed through high-speed (≈ 2500 frames/sec) motion pictures. The acoustic outputs of the flames are mapped with a condenser microphone. The recorded data are played back to obtain the amplitude, waveshapes, directionalities, and frequency spectra of the noise. Profound differences are found between the premixed and non-premixed flames in their structures and noise characteristics

Some experimental results on the L-star instability of metallized composite propellants

Experimental results are reported on the Lstar instability characteristics of three AP I composite propellants. The metal content of the propellants is 2%, 16%, and 16%. Chuffing, bulk mode oscillations, and time-independent combustion are observed with all three of these propellants. The stability boundary, defined as the boundary between time-independent and unstable combustion, is found to be well defined for two of the propellants in agreement with recognized trends available in the literature on other propellants. The frequency of bulk mode oscillations is presented as a function of the chamber characteristic length. One of the propellants tested has shown bulk mode instability at as high a pres sure as 217 psia. All of these tests were performed in a stainless steel L'~ motor with convenient, interchangeable stainless steel nozzles. The troublesome blockage of the small metal nozzles by the aluminum oxide slag was Overcome in most of these tests by the application of viscous silicone oil on the nozzle surface before each run. This technique is being pursued further, with plans for the inclusion of silicone compounds in propellant formulation, to reduce heat transfer to the inert nozzle

A new look at AP/composite propellant combustion

Some theoretical studies on the time-independent and oscillatory combustion of nonmetallized ammonium perchlorate (AP)/composite propellants are presented. A coherent and unified interpretation was made of the voluminous data available from experiments related to propellant combustion. Three fundamental hypotheses are introduced: the extent of propellant degradation at the vaporization step has to be specified through a scientific criterion; the condensed-phase degradation reaction of ammonium perchlorate to a vaporizable state is the overall rate-limiting step; gas-phase combustion rate is controlled by the mixing rate of fuel and oxidizer vapors. In the treatment of oscillatory combustion, the assumption of quasi-steady fluctuations in the gas phase is used to supplement these hypotheses