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

Defining Museum Intervention: An Analysis of James Putnam\u27s Time Machine

In his 2001 publication Art and Artifact: The Museum as Medium, independent curator James Putnam coins the term ‘museum intervention’ to describe a type of artwork created by some artists as a means to critique organizing principles of the museum. Putnam’s book analyzes examples of museum interventions, including his own 1994 exhibition, Time Machine: Ancient Egypt and Contemporary Art, but fails to offer a definition for the term. This thesis analyzes the trajectory of exhibition practices leading to the publication of the new term through an examination of historical changes in museum display. The paper then analyzes examples of museum intervention included in Putnam’s book in order to develop a definition for the term. The paper examines Time Machine in relation to the new definition and, contrary to Putnam’s assertions, concludes that the exhibition is not a museum intervention

Revisiting the Hanbury Brown-Twiss set-up for fractional statistics

The Hanbury Brown-Twiss experiment has proved to be an effective means of probing statistics of particles. Here, in a set-up involving edge-state quasiparticles in a fractional quantum Hall system, we show that a variant of the experiment composed of two sources and two sinks can be used to unearth fractional statistics. We find a clear cut signature of the statistics in the equal-time current-current correlation function for quasiparticle currents emerging from the two sources and collected at the sinks.Comment: 4 pages, 3 figure

Measuring Societal Biases in Text Corpora via First-Order Co-occurrence

Text corpora are used to study societal biases, typically through statistical models such as word embeddings. The bias of a word towards a concept is typically estimated using vectors similarity, measuring whether the word and concept words share other words in their contexts. We argue that this second-order relationship introduces unrelated concepts into the measure, which causes an imprecise measurement of the bias. We propose instead to measure bias using the direct normalized co-occurrence associations between the word and the representative concept words, a first-order measure, by reconstructing the co-occurrence estimates inherent in the word embedding models. To study our novel corpus bias measurement method, we calculate the correlation of the gender bias values estimated from the text to the actual gender bias statistics of the U.S. job market, provided by two recent collections. The results show a consistently higher correlation when using the proposed first-order measure with a variety of word embedding models, as well as a more severe degree of bias, especially to female in a few specific occupations

A Monte-Carlo Assessment Of The Life Cycle Impacts of Geothermal Energy For Power And Transportation

Increasing awareness of environmental issues surrounding power generationand transportation has increased interest in renewable energy sources such as geothermal.Renewable energy extraction is not without environmental cost, however; drillingoperations and construction of the facilities required for utilization can be resource intensive. Complete life cycle analysis (LCA) allows for impactcomparison between competing methods of power generation. The results are modular, allowingfor use in other product life cycles. One such life cycle is that of the transportation vehicle. An analysis of vehicle life cycles involving geothermal energy is performed employingthe The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model. Geothermal power haslarge variations between plants owing to differences in the hydrothermalreservoir chemistry and thermodynamic conditions. Due to these variations, a stochastic approachwas used to determine the amount of variation that is likely to be seen using this energy source.The results show geothermal power to have low environmental impact relative to othermethods of energy production for use in transportation

Quantum atom optics with fermions from molecular dissociation

We study a fermionic atom optics counterpart of parametric down-conversion with photons. This can be realized through dissociation of a Bose-Einstein condensate of molecular dimers consisting of fermionic atoms. We present a theoretical model describing the quantum dynamics of dissociation and find analytic solutions for mode occupancies and atomic pair correlations, valid in the short time limit. The solutions are used to identify upper bounds for the correlation functions, which are applicable to any fermionic system and correspond to ideal particle number-difference squeezingComment: Changes in response to referees' comments, updated reference