3,475 research outputs found
Topologies on Quantum Effects
Quantum effects play an important role in quantum measurement theory. The set
of all quantum effects can be organized into an algebraical structure called
effect algebra. In this paper, we study various topologies on the Hilbert space
effect algebra and the projection lattice effect algebra
Symmetric informationally complete positive operator valued measure and probability representation of quantum mechanics
Symmetric informationally complete positive operator valued measures
(SIC-POVMs) are studied within the framework of the probability representation
of quantum mechanics. A SIC-POVM is shown to be a special case of the
probability representation. The problem of SIC-POVM existence is formulated in
terms of symbols of operators associated with a star-product quantization
scheme. We show that SIC-POVMs (if they do exist) must obey general rules of
the star product, and, starting from this fact, we derive new relations on
SIC-projectors. The case of qubits is considered in detail, in particular, the
relation between the SIC probability representation and other probability
representations is established, the connection with mutually unbiased bases is
discussed, and comments to the Lie algebraic structure of SIC-POVMs are
presented.Comment: 22 pages, 1 figure, LaTeX, partially presented at the Workshop
"Nonlinearity and Coherence in Classical and Quantum Systems" held at the
University "Federico II" in Naples, Italy on December 4, 2009 in honor of
Prof. Margarita A. Man'ko in connection with her 70th birthday, minor
misprints are corrected in the second versio
Zika virus preferentially replicates in the female reproductive tract after vaginal inoculation of rhesus macaques.
Zika virus (ZIKV) is a mosquito-transmitted virus that can cause severe defects in an infected fetus. ZIKV is also transmitted by sexual contact, although the relative importance of sexual transmission is unclear. To better understand the role of sexual transmission in ZIKV pathogenesis, a nonhuman primate (NHP) model of vaginal transmission was developed. ZIKV was readily transmitted to mature cycling female rhesus macaque (RM) by vaginal inoculation with 104-106 plaque-forming units (PFU). However, there was variability in susceptibility between the individual RM with 1->8 vaginal inoculations required to establish infection. After treatment with Depoprovera, a widely used contraceptive progestin, two RM that initially resisted 8 vaginal ZIKV inoculations became infected after one ZIKV inoculation. Thus, Depoprovera seemed to enhance susceptibility to vaginal ZIKV transmission. Unexpectedly, the kinetics of virus replication and dissemination after intravaginal ZIKV inoculation were markedly different from RM infected with ZIKV by subcutaneous (SQ) virus inoculation. Several groups have reported that after SQ ZIKV inoculation vRNA is rapidly detected in blood plasma with vRNA less common in urine and saliva and only rarely detected in female reproductive tract (FRT) secretions. In contrast, in vaginally inoculated RM, plasma vRNA is delayed for several days and ZIKV replication in, and vRNA shedding from, the FRT was found in all 6 animals. Further, after intravaginal transmission ZIKV RNA shedding from FRT secretions was detected before or simultaneously with plasma vRNA, and persisted for at least as long. Thus, ZIKV replication in the FRT was independent of, and often preceded virus replication in the tissues contributing to plasma vRNA. These results support the conclusion that ZIKV preferentially replicates in the FRT after vaginal transmission, but not after SQ transmission, and raise the possibility that there is enhanced fetal infection and pathology after vaginal ZIKV transmission compared to a mosquito transmitted ZIKV
A CRASH simulation of the contribution of binary stars to the epoch of reionization
We use a set of 3D radiative transfer simulations to study the effect that a
large fraction of binary stars in galaxies during the epoch of reionization has
on the physical properties of the intergalactic medium (i.e. the gas
temperature and the ionization state of hydrogen and helium), on the topology
of the ionized bubbles and on the 21 cm power spectra. Consistently to previous
literature, we find that the inclusion of binary stars can speed up the
reionization process of HI and HeI, while HeII reionization is still dominated
by more energetic sources, especially accreting black holes. The earlier
ionization attained with binary stars allows for more time for cooling and
recombination, so that gas fully ionized by binary stars is typically colder
than that ionized by single stars at any given redshift. With the same volume
averaged ionization fraction, the inclusion of binary stars results in fewer
small ionized bubbles and more large ones, with visible effects also on the
large scales of the 21 cm power spectrum.Comment: 14 pages, 11 figures, MNRAS accepte
Flavour Changing Neutral Currents, Weak-Scale Scalars and Rare Top Decays
We examine the decays and in the Standard
Model with an extra scalar doublet and no discrete symmetry preventing
tree-level flavour changing neutral currents. The Yukawa couplings of the new
scalars are assumed to be proportional to fermion masses, evading bounds on
FCNC's from the light quark sector. These rare top decays may be visible at the
SSC.Comment: (some wording changed, and several references added) 13 pages, 2
figures included, uses harvmac.tex and epsf.tex, UCSD/PTH 93-0
Probing the high-z IGM with the hyperfine transition of He
The hyperfine transition of He at 3.5cm has been thought as a probe
of the high-z IGM since it offers a unique insight into the evolution of the
helium component of the gas, as well as potentially give an independent
constraint on the 21cm signal from neutral hydrogen. In this paper, we use
radiative transfer simulations of reionization driven by sources such as stars,
X-ray binaries, accreting black holes and shock heated interstellar medium, and
simulations of a high-z quasar to characterize the signal and analyze its
prospects of detection. We find that the peak of the signal lies in the range
1-50 K for both environments, but while around the quasar it is always in
emission, in the case of cosmic reionization a brief period of absorption is
expected. As the evolution of HeII is determined by stars, we find that it is
not possible to distinguish reionization histories driven by more energetic
sources. On the other hand, while a bright QSO produces a signal in 21cm that
is very similar to the one from a large collection of galaxies, its signature
in 3.5cm is very peculiar and could be a powerful probe to identify the
presence of the QSO. We analyze the prospects of the signal's detectability
using SKA1-mid as our reference telescope. We find that the noise power
spectrum dominates over the power spectrum of the signal, although a modest S/N
ratio can be obtained when the wavenumber bin width and the survey volume are
sufficiently large.Comment: 10 pages, 13 figures, accepted for publication in MNRA
Observing the Redshifted 21 cm Signal around a Bright QSO at z ∼ 10
We use hydrodynamics and radiative transfer simulations to study the 21 cm signal around a bright QSO at z ~ 10. Due to its powerful UV and X-ray radiation, the QSO quickly increases the extent of the fully ionized bubble produced by the pre-existing stellar type sources, in addition to partially ionizing and heating the surrounding gas. As expected, a longer QSO lifetime, t QSO, results in a 21 cm signal in emission located at increasingly larger angular radii, θ, and covering a wider range of θ. Similar features can be obtained with a higher galactic emissivity efficiency, f UV, such that determining the origin of a large ionized bubble (i.e., QSO versus stars) is not straightforward. Such degeneracy could be reduced by taking advantage of the finite light travel time effect, which is expected to affect an H ii region produced by a QSO differently from one created by stellar type sources. From an observational point of view, we find that the 21 cm signal around a QSO at various QSO could be detected by Square Kilometre Array1-low instrument with a high signal-to-noise ratio (S/N). As a reference, for t QSO = 10 Myr, a S/N ~ 8 is expected assuming that no pre-heating of the intergalactic medium has taken place due to high-z energetic sources, while it can reach values above 10 in cases of pre-heating. Observations of the 21 cm signal from the environment of a high-z bright QSO could then be used to set constraints on its lifetime, as well as to reduce the degeneracy between f UV and t QSO
Symplectic geometry of quantum noise
We discuss a quantum counterpart, in the sense of the Berezin-Toeplitz
quantization, of certain constraints on Poisson brackets coming from "hard"
symplectic geometry. It turns out that they can be interpreted in terms of the
quantum noise of observables and their joint measurements in operational
quantum mechanics. Our findings include various geometric mechanisms of quantum
noise production and a noise-localization uncertainty relation. The methods
involve Floer theory and Poisson bracket invariants originated in function
theory on symplectic manifolds.Comment: Revised version, 57 pages, 3 figures. Incorporates arXiv:1203.234
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