Resonance instability of primordial gravitational waves during inflation in Chern–Simons gravity

We investigate axion inflation where the gravitational Chern–Simons term is coupled to a periodic function of the inflaton. We find that tensor perturbations with different polarizations are amplified in different ways by the Chern–Simons coupling. Depending on the model parameters, the resonance amplification results in a parity-violating peak or a board plateau in the energy spectrum of gravitational waves, and the sharp cutoff in the infrared region constitutes a characteristic distinguishable from stochastic gravitational wave backgrounds produced by matter fields in Einstein gravity.

A Compact CPW Bandpass Filter using Folded Lines for UWB Applications

A compact CPW bandpass filter with asymmetrical folded parallel lines is proposed. Initially a parallel coupled filter is designed at center frequency then for size miniaturization the parallel lines are folded. thenthe filter convert in to CPW configuration to take the advantages of CPW geometry for achieving sharp cutoff characteristics. Total size of the filter is 7.55x7mm.

Snapping Back: Food Stamp Bans and Criminal Recidivism

I estimate the effect of access to food stamps on criminal recidivism. In 1996, a federal welfare reform imposed a lifetime ban from food stamps on convicted drug felons. Florida modified this ban, restricting it to drug traffickers who commit their offense on or after August 23, 1996. I exploit this sharp cutoff in a regression discontinuity design and find that the ban increases recidivism among drug traffickers. The increase is driven by financially motivated crimes, suggesting that the cut in benefits causes ex-convicts to return to crime to make up for the lost transfer income. (JEL H75, I38, K42)

NEW TYPE OF NEARLY MONOTONIC PASSBAND FILTERS WITH SHARP CUTOFF

New type of nearly monotonic rational function with one pair of zeros on imaginary axis has been proposed. By using these new functions with zeros as a parameter, it is possible to make tradeoff between minimum stopband attenuation and selectivity of the amplitude characteristic. In order to present efficiency of the proposed filter, comparison with allpole filter monotonic in the passband and inverse Chebyshev filter is presented. Also, design example for the seventh order new type lowpass filter is given.

On the Arbitrariness Objection to the Threshold View

Proponents of the ‘Threshold View’ have held that to believe a proposition is to be sufficiently confident of the proposition’s truth, but that there is no sharp cutoff between degrees of confidence that constitute belief and degrees of confidence that do not. Brian Weatherson has objected that no plausible account of vagueness can support this view. In this paper, I reply to Weatherson’s objection. Along the way, I identify a way in which one might hope to maintain the Threshold View without a fuzzy threshold, and I reformulate the Threshold View to accommodate fuzzy thresholds without begging substantive questions about vagueness.

Design and Optimization of Thermal Selective Emitters for High-Efficiency Thermophotovoltaic (TPV) Power Generation

Thermophotovoltaic (TPV) devices are popular energy converters due to providing low noise, low thermal-mechanical stresses and portability. The conversion efficiency of TPVs is still low due to mistuned spectral properties between thermal selective emitters and the TPV cell. Using thermal selective emitters that are well-matched to the TPV cell spectrum enhances the conversion efficiency of TPVs. Several thermal selective emitters, composed of 1-D complex multilayer structures with rectangular gratings, have been proposed. Cost, fabrication and stability factors have been major problems for their application on TPV modules. In this paper, a 1-D tungsten thermal emitter is optimized which exhibits close to blackbody emittance near the band-gap of a GaInAsSb TPV cell and sharp cutoff for longer wavelengths. The emitter is at 1200K, and is designed and optimized by modeling triangular grooves to excite localized groove modes which are well-matched to the GaInAsSb TPV cell external quantum efficiency (EQE) for high efficiency energy conversion. We suggest that a quasi-monochromatic, narrow-band and coherent emitter at a frequency near the energy band-gap of the converter is an ideal source to achieve high conversion efficiency.