Photon Bunching at TeV Energies

Harwit, Protheroe, and Biermann (1999) recently proposed that Bose-Einstein photon bunching might significantly affect the interpretation of Cerenkov counts of TeV gamma photons. Here, we show that a combination of two recent results of Aharonian et al. (2000) and Aharonian et al. (2001) permits us to set new, more stringent upper limits of $\lesssim 10$ on the fractional amount of photon bunching in the 7-10 TeV radiation from Markarian 501. Potential bunching at even higher energies should nevertheless continue to be investigated for this and other TeV sources, since a clear understanding of TeV energy spectra is required to unambiguously determine the spectral energy density of the mid-infrared extragalactic background

Simple applications of Noether's first theorem in quantum mechanics and electromagnetism

Internal global symmetries exist for the free non-relativistic Schr\"{o}dinger particle, whose associated Noether charges--the space integrals of the wavefunction and the wavefunction multiplied by the spatial coordinate--are exhibited. Analogous symmetries in classical electromagnetism are also demonstrated.Comment: 12 page

Observing the present and considering the past to ponder the future

No abstract available

Auroral zone electron precipitation accompanying a sudden impulse in the geomagnetic field

Auroral zone electron precipitation accompanying sudden commencement of geomagnetic storm

Variable ratio beam splitter for laser applications

Beam splitter employing birefringent optics provides either widely different or precisely equal beam ratios, it can be used with laser light source systems for interferometry of lossy media, holography, scattering measurements, and precise beam ratio applications

Reflectance measurements

The productivity of spectroreflectometer equipment and operating personnel and the accuracy and sensitivity of the measurements were investigated. Increased optical sensitivity and better design of the data collection and processing scheme to eliminate some of the unnecessary present operations were conducted. Two promising approaches to increased sensitivity were identified, conventional processing with error compensation and detection of random noise modulation

Detection and location of metallic objects imbedded in nonmetallic structures

Small battery operated eddy current proximity measuring device detects and locates metal objects the size of a dime at distances up to one foot within nonmetallic structures. This device weighs approximately two pounds, occupies approximately 60 cubic inches, and is battery powered

Aspects of Objectivity in Quantum Mechanics

The purpose of the paper is to explore different aspects of the covariance of (mostly) non-relativistic quantum mechanics. First, doubts are expressed concerning the claim that gauge fields can be 'generated' by way of imposition of (local) gauge covariance of the single-particle wave equation. Then a brief review is given of Galilean covariance in the general case of external fields, and the connection between Galilean boosts and gauge transformations. Under time-dependent translations (and hence non-instantaneous boosts) the geometric phase associated with Schrödinger evolution is non-invariant, and the significance of this result is briefly analysed. The covariance properties of Schrödinger dynamics are then brought to bear on certain versions of the modal interpretation of quantum mechanics. The conclusion that it is only relational properties that can be considered coordinate- or gauge-independent elements of reality is reinforced by appeal to the theory of quantum reference frames due to Aharonov and Kauffher. (This paper appeared in "From Physics to Philosophy", J. Butterfield and C. Pagonis (eds.), Cambridge University Press (1999); pp. 45-70.