5,216 research outputs found
Rotation and Spin in Physics
We delineate the role of rotation and spin in physics, discussing in order
Newtonian classical physics, special relativity, quantum mechanics, quantum
electrodynamics and general relativity. In the latter case, we discuss the
generalization of the Kepler formula to post-Newtonian order )
including spin effects and two-body effects. Experiments which verify the
theoretical results for general relativistic spin-orbit effects are discussed
as well as efforts being made to verify the spin-spin effects
Transformed Dissipation in Superconducting Quantum Circuits
Superconducting quantum circuits must be designed carefully to avoid
dissipation from coupling to external control circuitry. Here we introduce the
concept of current transformation to quantify coupling to the environment. We
test this theory with an experimentally-determined impedance transformation of
and find quantitative agreement better than a factor of 2 between
this transformation and the reduced lifetime of a phase qubit coupled to a
tunable transformer. Higher-order corrections from quantum fluctuations are
also calculated with this theory, but found not to limit the qubit lifetime. We
also illustrate how this simple connection between current and impedance
transformation can be used to rule out dissipation sources in experimental
qubit systems.Comment: 4 pages, 4 figure
Signatures of the Youngest Starbursts: Optically-thick Thermal Bremsstrahlung Radio Sources in Henize 2-10
VLA radio continuum imaging reveals compact (<8 pc) ~1 mJy radio sources in
the central 5" starburst region of the blue compact galaxy Henize 2-10. We
interpret these radio knots as extremely young, ultra-dense HII regions. We
model their luminosities and spectral energy distributions, finding that they
are consistent with unusually dense HII regions having electron densities, 1500
cm^-3 < n_e < 5000 cm^-3, and sizes of 3-8 pc. Since these H II regions are not
visible in optical images, we propose that the radio data preferentially reveal
the youngest, densest, and most highly obscured starforming events. Energy
considerations imply that each of the five \HII regions contains ~750 O7V
equivalent stars, greater than the number found in 30 Doradus in the LMC. The
high densities imply an over-pressure compared to the typical interstellar
medium so that such objects must be short-lived (<0.5 Myr expansion
timescales). We conclude that the radio continuum maps reveal the very young
(<0.5 Myr) precursors of ``super starclusters'' or ``proto globular clusters''
which are prominent at optical and UV wavelengths in He 2-10. If the
ultra-dense HII regions are typical of those which we predict will be found in
other starbursting systems, then super starclusters spend 15% of their lifetime
in heavily-obscured environments, similar to Galactic ultra-compact HII
regions. This body of work leads us to propose that massive extragalactic star
clusters (i.e. proto globular clusters) with ages <10^6 yr may be most easily
identified by finding compact radio sources with optically-thick thermal
bremsstrahlung spectral signatures.Comment: AASTeX, 8 figures 2 included with psfig in text; other 6 in jpeg
format; Postscript versions of figures may be found at
http://zem.ucolick.org/chip/Research/young_clusters.html -- Accepted for
publication in the Astrophysical Journa
Balmer and Metal Absorption Feature Gradients in M32
Spectra from MDM Observatory are used to assess Lick/IDS feature strength
gradients inside the half-light radius of the compact Local Group elliptical
galaxy M32. All but a few (of 24 measured) indices show a statistically
significant gradient. Comparing with models, the index gradients indicate a
mean age and abundance gradient in the sense that the nucleus is a factor of
2.5 younger and a factor of 0.3 dex more metal-rich than at 1 effective radius.
This conclusion is only weakly dependent on which index combinations are used
and is robust to high accuracy. Stars near the M32 nucleus have a mean age and
heavy element abundance [M/H] of (4.7 Gyr, +0.02), judging from models by
Worthey with variable abundance ratios. This result has very small formal
random errors, although, of course, there is significant age-metallicity
degeneracy along an (age, abundance) line segment from (5.0 Gyr, 0.00) to (4.5
Gyr, +0.05). An abundance pattern of [C/M]=+0.077, [N/M]=-0.13, [Mg/M]=-0.18,
[Fe/M]~0.0, and [Na/M]=+0.12 is required to fit the feature data, with a
fitting precision of about 0.01 dex. Model uncertainties make the accuracies of
these values at least twice the magnitude of the precision. Forcing
scaled-solar abundances does not change the age very much, but it increases the
rms goodness of model-data fit by a factor of 3 and broadens the allowed range
of age to Gyr. The overall abundance pattern contrasts with larger
elliptical galaxies, in which all measurable lighter elements are enhanced
relative to iron and calcium.Comment: 23 pages, 9 figures, Astronomical Journal, in pres
A multi-layer extension of the stochastic heat equation
Motivated by recent developments on solvable directed polymer models, we
define a 'multi-layer' extension of the stochastic heat equation involving
non-intersecting Brownian motions.Comment: v4: substantially extended and revised versio
World Athletics regulations unfairly affect female athletes with differences in sex development
World Athletics have introduced regulations preventing female athletes with certain differences in sex development from competing in the female category. We argue these regulations are not justified and should be removed. Firstly, we examine the reasoning and evidence underlying the position that these athletes have a substantial mean difference in performance from other female athletes such that it constitutes an advantage, and argue it is not sufficient. Secondly, if an advantage does exist, it needs to be demonstrated it is unfair. We argue the advantage would not be unfair because to say otherwise relies on a presupposition about whether these athletes are female, which involves contradictory and inconsistent definitions of sex. Thirdly, we contend that even if it is established that there is an advantage and it is unfair, the response of requiring athletes to take testosterone-suppressing medication is not appropriate and is unfair
Untangling Source-To-Sink Geochemical Signals in a ~3.5 Ga Martian Lake: Sedimentology and Geochemistry of the Murray Formation
Sedimentary rocks are historical archives of planetary surface processes; their grains, textures, and chemistry integrate the effects of source terrains, paleoclimatic conditions, weathering and transport processes, authigenic mineral precipitation, and diagenesis, which records groundwater chemistry through time. Source to Sink basin analysis seeks to constrain the influence of each of these different signals through sedimentary and geochemical analyses. Here, we use Mars Science Laboratory (MSL) Curiosity rover images and geochemical and mineralogical data from a traverse across a portion of the Murray formationthe lowermost unit exposed in the Gale crater central moundto begin to constrain the aspects of the source to sink system that formed this Martian mudstone between 3.7 and 3.2 Ga
Vector meson dominance and the rho meson
We discuss the properties of vector mesons, in particular the rho^0, in the
context of the Hidden Local Symmetry (HLS) model. This provides a unified
framework to study several aspects of the low energy QCD sector. Firstly, we
show that in the HLS model the physical photon is massless, without requiring
off field diagonalization. We then demonstrate the equivalence of HLS and the
two existing representations of vector meson dominance, VMD1 and VMD2, at both
tree level and one loop order. Finally the S matrix pole position is shown to
provide a model and process independent means of specifying the rho mass and
width, in contrast to the real axis prescription currently used in the Particle
Data Group tables.Comment: 18 pages, REVTE
Anomalous diffusion in quantum Brownian motion with colored noise
Anomalous diffusion is discussed in the context of quantum Brownian motion
with colored noise. It is shown that earlier results follow simply and directly
from the fluctuation-dissipation theorem. The limits on the long-time
dependence of anomalous diffusion are shown to be a consequence of the second
law of thermodynamics. The special case of an electron interacting with the
radiation field is discussed in detail. We apply our results to wave-packet
spreading
Quantum process tomography of two-qubit controlled-Z and controlled-NOT gates using superconducting phase qubits
We experimentally demonstrate quantum process tomography of controlled-Z and
controlled-NOT gates using capacitively-coupled superconducting phase qubits.
These gates are realized by using the state of the phase qubit. We
obtain a process fidelity of 0.70 for the controlled-phase and 0.56 for the
controlled-NOT gate, with the loss of fidelity mostly due to single-qubit
decoherence. The controlled-Z gate is also used to demonstrate a two-qubit
Deutsch-Jozsa algorithm with a single function query.Comment: 10 pages, 8 figures, including supplementary informatio
- …