3,116 research outputs found
A general purpose wideband optical spatial frequency spectrum analyzer
The light scattered at various angles by a transparent media is studied. An example of these applications is the optical Fourier spectrum measurement resulting from various spatial frequencies which were recorded on a photographic emulsion. A method for obtaining these measurements consists of illuminating the test object with parallel monochromatic light. A stationary lens, placed in the resulting wavefield at a distance of one focal length from the object, will focus parallel waves emanating from the test object at a point lying in the focal plane of the lens. A light detector with a small filtering aperture is then used to measure the intensity variation of the light in the focal or transform plane of the lens. Such measurements require the use of a lens which is highly corrected for all of the common aberrations except chromatic aberration
Between fact and fiction: Demarcating science from non-science in popular physics books
Accepted versio
Left unsaid: the marginalisation of scientist-critics in the media coverage of controversial technologies
Submitted versio
Cauchy horizon singularity without mass inflation
A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the
nature of the singularity along the Cauchy horizon of a charged spherically
symmetric black hole. For these solutions, conditions may prevail under which
the mass function is bounded and yet the curvature scalar
diverges.Comment: typeset in RevTex, 13 page
Pair Creation of Black Holes by Domain Walls
In this paper we study the production of pairs of neutral and charged black
holes by domain walls, finding classical solutions and calculating their
classical actions. We find that neutral black holes whose creation is mediated
by Euclidean instantons must be produced mutually at rest with respect to one
another, but for charged black holes a new type of instanton is possible in
which after formation the two black holes accelerate away from one another.
These new types of instantons are not possible in Einstein-Maxwell theory with
a cosmological constant. We also find that the creation of non-orientable black
hole solutions can be mediated by Euclidean instantons and that in addition if
one is prepared to consider entirely Lorentzian no-boundary type contributions
to the path integral then mutually accelerating pairs may be created even in
the neutral case. Finally we consider the production of Kaluza-Klein monopoles
both by a standard cosmological term and in the presence of a domain wall. We
find that compactification is accompanied by the production of pairs of
Kaluza-Klein monopoles.Comment: 22 pages (REVTeX with AMS Symbols) with 5 postscript figures attached
in a single uuencoded, g-zipped, tar file at end of tex fil
Ultrasmall-in-Nano: Why Size Matters
Gold nanoparticles (AuNPs) are continuing to gain popularity in the field of nanotechnology. New methods are continuously being developed to tune the particles’ physicochemical properties, resulting in control over their biological fate and applicability to in vivo diagnostics and therapy. This review focuses on the effects of varying particle size on optical properties, opsonization, cellular internalization, renal clearance, biodistribution, tumor accumulation, and toxicity. We review the common methods of synthesizing ultrasmall AuNPs, as well as the emerging constructs termed ultrasmall-in-nano—an approach which promises to provide the desirable properties from both ends of the AuNP size range. We review the various applications and outcomes of ultrasmall-in-nano constructs in vitro and in vivo
Charged gravitational instantons in five-dimensional Einstein-Gauss-Bonnet-Maxwell theory
We study a solution of the Einstein-Gauus-Bonnet theory in 5 dimensions
coupled to a Maxwell field, whose euclidean continuation gives rise to an
instanton describing black hole pair production. We also discuss the dual
theory with a 3-form field coupled to gravity.Comment: 8 pages, plain Te
Cosmic Censorship: As Strong As Ever
Spacetimes which have been considered counter-examples to strong cosmic
censorship are revisited. We demonstrate the classical instability of the
Cauchy horizon inside charged black holes embedded in de Sitter spacetime for
all values of the physical parameters. The relevant modes which maintain the
instability, in the regime which was previously considered stable, originate as
outgoing modes near to the black hole event horizon. This same mechanism is
also relevant for the instability of Cauchy horizons in other proposed
counter-examples of strong cosmic censorship.Comment: 4 pages RevTeX style, 1 figure included using epsfi
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