2,778 research outputs found
Are the school prevention programmes - aimed at de-normalizing smoking among youths - beneficial in the long term? An example from the Smoke Free Class Competition in Italy
Tobacco smoking by young people is of great concern because it usually leads to regular smoking, nicotine addiction and quitting difficulties. Young people "hooked" by tobacco maintain the profits of the tobacco industry by replacing smokers who quit or die. If new generations could be tobacco-free, as supported by tobacco endgame strategies, the tobacco epidemic could end within decades. Smoking prevention programmes for teens are offered by schools with the aim to prevent or delay smoking onset. Among these, the Smoke Free Class Competition (SFC) was widely implemented in Europe. Its effectiveness yielded conflicting results, but it was only evaluated at short/medium term (6 - 18 months). The aim of this study is to evaluate its effectiveness after a longer follow-up (3 to 5 years) in order to allow enough time for the maturing of the students and the internalization of the experience and its contents. Fifteen classes were randomly sampled from two Italian high schools of Bologna province that regularly offered the SFC to first year students; 382 students (174 participating in the SFC and 208 controls) were retrospectively followed-up and provided their "smoking histories". At the end of their last year of school (after 5 years from the SFC), the percentage of students who stated that they were regular smokers was lower among the SFC students than in controls: 13.5% vs 32.9% (p=0.03). From the students' "smoking histories", statistically significant protective ORs were observed for SFC students at the end of 1st and 5th year: 0.42 (95% CI 0.19-0.93) and 0.32 (95% CI 0.11-0.91) respectively. Absence of smokers in the family was also a strongly statistically significant factor associated with being a non-smoker student. These results suggest that SFC may have a positive impact on lowering the prevalence of smoking in the long term (5 years)
Decoupling a Cooper-pair box to enhance the lifetime to 0.2 ms
We present a circuit QED experiment in which a separate transmission line is
used to address a quasi-lumped element superconducting microwave resonator
which is in turn coupled to an Al/AlO/Al Cooper-pair box (CPB) charge
qubit. In our measurements we find a strong correlation between the measured
lifetime of the CPB and the coupling between the qubit and the transmission
line. By monitoring perturbations of the resonator's 5.44 GHz resonant
frequency, we have measured the spectrum, lifetime (), Rabi, and Ramsey
oscillations of the CPB at the charge degeneracy point while the CPB was
detuned by up to 2.5 GHz . We find a maximum lifetime of the CPB was s for to 4.5 GHz. Our measured 's are consistent with
loss due to coupling to the transmission line, spurious microwave circuit
resonances, and a background decay rate on the order of
s of unknown origin, implying that the loss tangent in the AlO
junction barrier must be less than about at 4.5 GHz, about 4
orders of magnitude less than reported in larger area Al/AlO/Al tunnel
junctions
Quantum Magnetic Algebra and Magnetic Curvature
The symplectic geometry of the phase space associated with a charged particle
is determined by the addition of the Faraday 2-form to the standard structure
on the Euclidean phase space. In this paper we describe the corresponding
algebra of Weyl-symmetrized functions in coordinate and momentum operators
satisfying nonlinear commutation relations. The multiplication in this algebra
generates an associative product of functions on the phase space. This product
is given by an integral kernel whose phase is the symplectic area of a
groupoid-consistent membrane. A symplectic phase space connection with
non-trivial curvature is extracted from the magnetic reflections associated
with the Stratonovich quantizer. Zero and constant curvature cases are
considered as examples. The quantization with both static and time dependent
electromagnetic fields is obtained. The expansion of the product by the
deformation parameter, written in the covariant form, is compared with the
known deformation quantization formulas.Comment: 23 page
GR 290 (Romano's Star): 2. Light history and evolutionary state
We have built the historical light curve of the luminous variable GR 290 back
to 1901, from old observations of the star found in several archival plates of
M 33. These old recordings together with published and new data show that for
at least half a century the star was in a low luminosity state, with B ~18.
After 1960, five large variability cycles of visual luminosity were recorded.
The amplitude of the oscillations was seen increasing towards the 1992-1994
maximum, then decreasing during the last maxima. The recent light curve
indicates that the photometric variations have been quite similar in all the
bands, and that the B-V color index has been constant within +/-0.1 m despite
the 1.5m change of the visual luminosity. The spectrum of GR 290 at the large
maximum of 1992-94, was equivalent to late-B type, while, during 2002-2014, it
has varied between WN10h-11h near the visual maxima to WN8h-9h at the
luminosity minima. We have detected, during this same period, a clear
anti-correlation between the visual luminosity, the strength of the HeII 4686 A
emission line, the strength of the 4600-4700 A lines blend and the spectral
type. From a model analysis of the spectra collected during the whole 2002-2014
period we find that the Rosseland radius R_{2/3}, changed between the minimum
and maximum luminosity phases by a factor of 3, while T_eff varied between
about 33,000 K and 23,000 K. The bolometric luminosity of the star was not
constant, but increased by a factor of ~1.5 between minimum and maximum
luminosity, in phase with the apparent luminosity variations. In the light of
current evolutionary models of very massive stars, we find that GR 290 has
evolved from a ~60 M_Sun progenitor star and should have an age of about 4
million years. We argue that it has left the LBV stage and is moving to a
Wolf-Rayet stage of late nitrogen spectral type.Comment: Accepted on The Astronomical Journal, 10 figures. Replaced because
the previous uploaded file was that without the final small corrections
requested by the refere
Quantum Mechanics as an Approximation to Classical Mechanics in Hilbert Space
Classical mechanics is formulated in complex Hilbert space with the
introduction of a commutative product of operators, an antisymmetric bracket,
and a quasidensity operator. These are analogues of the star product, the Moyal
bracket, and the Wigner function in the phase space formulation of quantum
mechanics. Classical mechanics can now be viewed as a deformation of quantum
mechanics. The forms of semiquantum approximations to classical mechanics are
indicated.Comment: 10 pages, Latex2e file, references added, minor clarifications mad
The -theorem and the Asymptotics of 4D Quantum Field Theory
We study the possible IR and UV asymptotics of 4D Lorentz invariant unitary
quantum field theory. Our main tool is a generalization of the
Komargodski-Schwimmer proof for the -theorem. We use this to rule out a
large class of renormalization group flows that do not asymptote to conformal
field theories in the UV and IR. We show that if the IR (UV) asymptotics is
described by perturbation theory, all beta functions must vanish faster than
as (). This implies that the
only possible asymptotics within perturbation theory is conformal field theory.
In particular, it rules out perturbative theories with scale but not conformal
invariance, which are equivalent to theories with renormalization group
pseudocycles. Our arguments hold even for theories with gravitational
anomalies. We also give a non-perturbative argument that excludes theories with
scale but not conformal invariance. This argument holds for theories in which
the stress-energy tensor is sufficiently nontrivial in a technical sense that
we make precise.Comment: 41 pages, 2 figures. v2: Arguments clarified, some side comments
corrected, connection to previous work by Jack and Osborn described,
conclusions unaffecte
Heisenberg Evolution WKB and Symplectic Area Phases
The Schrodinger and Heisenberg evolution operators are represented in quantum
phase space by their Weyl symbols. Their semiclassical approximations are
constructed in the short and long time regimes. For both evolution problems,
the WKB representation is purely geometrical: the amplitudes are functions of a
Poisson bracket and the phase is the symplectic area of a region in phase space
bounded by trajectories and chords. A unified approach to the Schrodinger and
Heisenberg semiclassical evolutions is developed by introducing an extended
phase space. In this setting Maslov's pseudodifferential operator version of
WKB analysis applies and represents these two problems via a common higher
dimensional Schrodinger evolution, but with different extended Hamiltonians.
The evolution of a Lagrangian manifold in the extended phase space, defined by
initial data, controls the phase, amplitude and caustic behavior. The
symplectic area phases arise as a solution of a boundary condition problem.
Various applications and examples are considered.Comment: 32 pages, 7 figure
Symplectic areas, quantization, and dynamics in electromagnetic fields
A gauge invariant quantization in a closed integral form is developed over a
linear phase space endowed with an inhomogeneous Faraday electromagnetic
tensor. An analog of the Groenewold product formula (corresponding to Weyl
ordering) is obtained via a membrane magnetic area, and extended to the product
of N symbols. The problem of ordering in quantization is related to different
configurations of membranes: a choice of configuration determines a phase
factor that fixes the ordering and controls a symplectic groupoid structure on
the secondary phase space. A gauge invariant solution of the quantum evolution
problem for a charged particle in an electromagnetic field is represented in an
exact continual form and in the semiclassical approximation via the area of
dynamical membranes.Comment: 39 pages, 17 figure
Scale without Conformal Invariance at Three Loops
We carry out a three-loop computation that establishes the existence of scale
without conformal invariance in dimensional regularization with the MS scheme
in d=4-epsilon spacetime dimensions. We also comment on the effects of scheme
changes in theories with many couplings, as well as in theories that live on
non-conformal scale-invariant renormalization group trajectories. Stability
properties of such trajectories are analyzed, revealing both attractive and
repulsive directions in a specific example. We explain how our results are in
accord with those of Jack & Osborn on a c-theorem in d=4 (and d=4-epsilon)
dimensions. Finally, we point out that limit cycles with turning points are
unlike limit cycles with continuous scale invariance.Comment: 21 pages, 3 figures, Erratum adde
Mixed Weyl Symbol Calculus and Spectral Line Shape Theory
A new and computationally viable full quantum version of line shape theory is
obtained in terms of a mixed Weyl symbol calculus. The basic ingredient in the
collision--broadened line shape theory is the time dependent dipole
autocorrelation function of the radiator-perturber system. The observed
spectral intensity is the Fourier transform of this correlation function. A
modified form of the Wigner--Weyl isomorphism between quantum operators and
phase space functions (Weyl symbols) is introduced in order to describe the
quantum structure of this system. This modification uses a partial Wigner
transform in which the radiator-perturber relative motion degrees of freedom
are transformed into a phase space dependence, while operators associated with
the internal molecular degrees of freedom are kept in their original Hilbert
space form. The result of this partial Wigner transform is called a mixed Weyl
symbol. The star product, Moyal bracket and asymptotic expansions native to the
mixed Weyl symbol calculus are determined. The correlation function is
represented as the phase space integral of the product of two mixed symbols:
one corresponding to the initial configuration of the system, the other being
its time evolving dynamical value. There are, in this approach, two
semiclassical expansions -- one associated with the perturber scattering
process, the other with the mixed symbol star product. These approximations are
used in combination to obtain representations of the autocorrelation that are
sufficiently simple to allow numerical calculation. The leading O(\hbar^0)
approximation recovers the standard classical path approximation for line
shapes. The higher order O(\hbar^1) corrections arise from the noncommutative
nature of the star product.Comment: 26 pages, LaTeX 2.09, 1 eps figure, submitted to 'J. Phys. B.
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