arXiv subjects

Stephen Boughn

Publications and source records attributed to Stephen Boughn.

27 records · Page 2Linked to original sources

arXiv2011

Hasenohrl and the Equivalence of Mass and Energy

In 1904 Austrian physicist Fritz Hasenohrl (1874-1915) examined blackbody radiation in a reflecting cavity. By calculating the work necessary to keep the cavity moving at a constant velocity against the radiation pressure he concluded that to a moving observer the energy of the radiation would appear to increase by an amount E=(3/8)mc^2, which in early 1905 he corrected to E=(3/4)mc^2. Because relativistic corrections come in at order v^2/c^2 and Hasenohrl's gedankenexperiment evidently required calculations only to order v/c, it is initially puzzling why he did not achieve the answer universally accepted today. Moreover, that $m$ should be equal to (4/3)E/c^2 has led commentators to believe that this problem is identical to the famous "4/3 problem" of the self-energy of the electron and they have invariably attributed Hasenohrl's mistake to neglect of the cavity stresses. We examine Hasenohrl's papers from a modern, relativistic point of view in an attempt to understand where exactly he went wrong. The problem turns out to be a rich and challenging one with strong resonances to matters that remain controversial. We give an acceptable relativistic solution to the conundrum and show that virtually everything ever written about Hasenohrl's thought experiment, including a 1923 paper by Enrico Fermi, is misleading if not incorrect.

physics.hist-ph↗

arXiv2010

"Quantum Interference with Slits" Revisited

Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.

quant-ph↗

arXiv2009

Nonquantum Gravity

One of the great challenges for 21st century physics is to quantize gravity and generate a theory that will unify gravity with the other three fundamental forces of nature. This paper takes the (heretical) point of view that gravity may be an inherently classical, i.e., nonquantum, phenomenon and investigates the experimental consequences of such a model. At present there is no experimental evidence of the quantum nature of gravity and the liklihood of definitive tests in the future is not at all certain. If gravity is, indeed, a nonquantum phenomenon, then it is suggested that evidence will most likely appear at mesoscopic scales.

gr-qc↗

arXiv2008

The Lorentz Force and the Radiation Pressure of Light

In order to make plausible the idea that light exerts a pressure on matter, some introductory physics texts consider the force exerted by an electromagnetic wave on an electron. The argument as presented is both mathematically incorrect and has several serious conceptual difficulties without obvious resolution at the classical, yet alone introductory, level. We discuss these difficulties and propose an alternate demonstration.

physics.class-ph↗

arXiv2006

Can Gravitons Be Detected?

Freeman Dyson has questioned whether any conceivable experiment in the real universe can detect a single graviton. If not, is it meaningful to talk about gravitons as physical entities? We attempt to answer Dyson's question and find it is possible concoct an idealized thought experiment capable of detecting one graviton; however, when anything remotely resembling realistic physics is taken into account, detection becomes impossible, indicating that Dyson's conjecture is very likely true. We also point out several mistakes in the literature dealing with graviton detection and production.

gr-qc↗

arXiv2006

Aspects of Graviton Detection: Graviton Emission and Absorption by Atomic Hydrogen

Graviton absorption cross sections and emission rates for hydrogen are calculated by both semi-classical and field theoretic methods. We point out several mistakes in the literature concerning spontaneous emission of gravitons and related phenomena, some of which are due to a subtle issue concerning gauge invariance of the linearized interaction Hamiltonian.

gr-qc↗

arXiv2004

Investigating the origins of the CMB-XRB cross correlation

Recently, we presented evidence for a cross-correlation of the WMAP satellite map of the cosmic microwave background (CMB) and the HEAO1 satellite map of the hard X-ray background (XRB) with a dimensionless amplitude of 0.14 +- 0.05 normalized to the product of the rms fluctuations of the CMB and XRB (Boughn & Crittenden, 2004). Such a correlation is expected in a universe dominated by a cosmological constant via the integrated Sachs-Wolfe (ISW) effect and the level of the correlation observed is consistent with that predicted by the currently favored Lambda cold dark matter model of the universe. Since this offers independent confirmation of the cosmological model, it is important to verify the origin of the correlation. Here we explore in detail some possible foreground sources of the correlation. The present evidence all supports an ISW origin.

astro-ph↗

arXiv2004

The large-scale bias of the hard X-ray background

Recent deep X-ray surveys combined with spectroscopic identification of the sources have allowed the determination of the rest-frame 2-8 keV luminosity as a function of redshift. In addition, an analysis of the HEAO1 A2 2-10 keV full-sky map of the X-ray background (XRB) reveals clustering on the scale of several degrees. Combining these two results in the context of the currently favored Lambda-CDM cosmological model implies an average X-ray bias factor, b_x, of b_x^2 = 1.12 +- 0.33, i.e., b_x = 1.06 +- 0.16. These error estimates include only statistical error; the systematic error sources, while comparable, appear to be sub-dominant. This result is in contrast to the large biases of some previous estimates and is more in line with current estimates of the optical bias of L* galaxies.

astro-ph↗

arXiv2003

A correlation of the cosmic microwave sky with large scale structure

We cross correlate the large-scale cosmic microwave background (CMB) sky measured by WMAP with two probes of large-scale structure at z ~ 1. The hard X-ray background, measured by the HEAO-1 satellite, is positively correlated with the WMAP data at the 2.5-3.0 sigma level. The number counts of radio galaxies in the NVSS survey are also correlated at a slightly weaker level (2.-2.5 sigma). These correlations appear to arise from both hemispheres on the sky and are resilient to changes in the levels of masking of the Galaxy and point sources, suggesting that foregrounds are not responsible for the signal. The implication is that some of the observed CMB fluctuations arise at low redshifts. The level of the correlations is consistent with that expected for the cosmological constant (Omega_Lambda = 0.72) concordance model resulting from the integrated Sachs-Wolfe effect. Thus, we may be observing dark energy's effect on the growth of structure.

astro-ph↗