34,051 research outputs found
Local light-ray rotation
We present a sheet structure that rotates the local ray direction through an
arbitrary angle around the sheet normal. The sheet structure consists of two
parallel Dove-prism sheets, each of which flips one component of the local
direction of transmitted light rays. Together, the two sheets rotate
transmitted light rays around the sheet normal. We show that the direction
under which a point light source is seen is given by a Mobius transform. We
illustrate some of the properties with movies calculated by ray-tracing
software.Comment: 9 pages, 6 figure
Metamaterials for light rays: ray optics without wave-optical analog in the ray-optics limit
Volumes of sub-wavelength electromagnetic elements can act like homogeneous
materials: metamaterials. In analogy, sheets of optical elements such as prisms
can act ray-optically like homogeneous sheet materials. In this sense, such
sheets can be considered to be metamaterials for light rays (METATOYs).
METATOYs realize new and unusual transformations of the directions of
transmitted light rays. We study here, in the ray-optics and scalar-wave
limits, the wave-optical analog of such transformations, and we show that such
an analog does not always exist. Perhaps, this is the reason why many of the
ray-optical possibilities offered by METATOYs have never before been
considered.Comment: 10 pages, 3 figures, references update
Electric field induced charge noise in doped silicon: ionization of phosphorus donors
We report low frequency charge noise measurement on silicon substrates with
different phosphorus doping densities. The measurements are performed with
aluminum single electron transistors (SETs) at millikelvin temperatures where
the substrates are in the insulating regime. By measuring the SET Coulomb
oscillations, we find a gate voltage dependent charge noise on the more heavily
doped substrate. This charge noise, which is seen to have a 1/f spectrum, is
attributed to the electric field induced tunneling of electrons from their
phosphorus donor potentials.Comment: 4 page, 3 figure
Displacement operators: the classical face of their quantum phase
In quantum mechanics, the operator representing the displacement of a system
in position or momentum is always accompanied by a path-dependent phase factor.
In particular, two non-parallel displacements in phase space do not compose
together in a simple way, and the order of these displacements leads to
different displacement composition phase factors. These phase factors are often
attributed to the nonzero commutator between quantum position and momentum
operators, but such a mathematical explanation might be unsatisfactory to
students who are after more physical insight. We present a couple of simple
demonstrations, using classical wave mechanics and classical particle
mechanics, that provide some physical intuition for the phase associated with
displacement operators.Comment: 14 pages, 4 figures, reorganized and reformatte
Mass inflation in a D dimensional Reissner-Nordstrom black hole: a hierarchy of particle accelerators ?
We study the geometry inside the event horizon of perturbed D dimensional
Reissner-Nordstrom-(A)dS type black holes showing that, similarly to the four
dimensional case, mass inflation also occurs for D>4. First, using the
homogeneous approximation, we show that an increase of the number of spatial
dimensions contributes to a steeper variation of the metric coefficients with
the areal radius and that the phenomenon is insensitive to the cosmological
constant in leading order. Then, using the code reported in arXiv:0904.2669
[gr-qc] adapted to D dimensions, we perform fully non-linear numerical
simulations. We perturb the black hole with a compact pulse adapting the pulse
amplitude such that the relative variation of the black hole mass is the same
in all dimensions, and determine how the black hole interior evolves under the
perturbation. We qualitatively confirm that the phenomenon is similar to four
dimensions as well as the behaviour observed in the homogeneous approximation.
We speculate about the formation of black holes inside black holes triggered by
mass inflation, and about possible consequences of this scenario.Comment: 8 pages, 6 figure
Interpretation of UV Absorption Lines in SN1006
We present a theoretical interpretation of the broad silicon and iron UV
absorption features observed with the Hubble Space Telescope in the spectrum of
the Schweizer-Middleditch star behind the remnant of Supernova 1006. These
features are caused by supernova ejecta in SN1006. We propose that the
redshifted SiII2 1260 A feature consists of both unshocked and shocked SiII.
The sharp red edge of the line at 7070 km/s indicates the position of the
reverse shock, while its Gaussian blue edge reveals shocked Si with a mean
velocity of 5050 km/s and a dispersion of 1240 km/s, implying a reverse shock
velocity of 2860 km/s. The measured velocities satisfy the energy jump
condition for a strong shock, provided that all the shock energy goes into
ions, with little or no collisionless heating of electrons. The line profiles
of the SiIII and SiIV absorption features indicate that they arise mostly from
shocked Si. The total mass of shocked and unshocked Si inferred from the SiII,
SiIII and SiIV profiles is M_Si = 0.25 \pm 0.01 Msun on the assumption of
spherical symmetry. Unshocked Si extends upwards from 5600 km/s. Although there
appears to be some Fe mixed with the Si at lower velocities < 7070 km/s, the
absence of FeII absorption with the same profile as the shocked SiII suggests
little Fe mixed with Si at higher (before being shocked) velocities. The column
density of shocked SiII is close to that expected for SiII undergoing steady
state collisional ionization behind the reverse shock, provided that the
electron to SiII ratio is low, from which we infer that most of the shocked Si
is likely to be of a fairly high degree of purity, unmixed with other elements.
We propose that the ambient interstellar density on the far side of SN1006 is
anomalously low compared to the density around the rest of the remnant. ThisComment: 24 pages, with 8 figures included. Accepted for publication in the
Astrophysical Journa
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