20,393 research outputs found
Apparatus for making curved reflectors Patent
Forming mold for polishing and machining curved solar magnesium reflector with reinforcing rib
Process sequence produces strong, lightweight reflectors of excellent quality
Large compound curved surfaces for collecting and concentrating radiation are fabricated by the use of several common machining and forming processes. Lightweight sectors are assembled into large reflectors. With this concept of fabrication, integrally stiffened reflective sectors up to 25 square feet in area have been produced
Method and apparatus for making curved reflectors Patent
Fabrication of curved reflector segments for solar mirro
Taylor-Lagrange renormalization scheme. Application to light-front dynamics
The recently proposed renormalization scheme based on the definition of field
operators as operator valued distributions acting on specific test functions is
shown to be very convenient in explicit calculations of physical observables
within the framework of light-front dynamics. We first recall the main
properties of this procedure based on identities relating the test functions to
their Taylor remainder of any order expressed in terms of Lagrange's formulae,
hence the name given to this scheme. We thus show how it naturally applies to
the calculation of state vectors of physical systems in the covariant
formulation of light-front dynamics. As an example, we consider the case of the
Yukawa model in the simple two-body Fock state truncation.Comment: 18 pages, 6 figures, introduction changed, corrected typos, to be
published in Physical Review
The fine-tuning problem revisited in the light of the Taylor-Lagrange renormalization scheme
We re-analyse the perturbative radiative corrections to the Higgs mass within
the Standard Model in the light of the Taylor-Lagrange renormalization scheme.
This scheme naturally leads to completely finite corrections, depending on an
arbitrary dimensionless scale. This formulation avoids very large individual
corrections to the Higgs mass. In other words, it is a confirmation that the
so-called fine-tuning problem in the Standard Model is just an artefact of the
regularization scheme and should not lead to any physical interpretation in
terms of the energy scale at which new physics should show up, nor to the
appearance of a new symmetry. We analyse the characteristic physical scales
relevant for the description of these radiative corrections.Comment: 8 pages, 2 figure
Exact Energy-Time Uncertainty Relation for Arrival Time by Absorption
We prove an uncertainty relation for energy and arrival time, where the
arrival of a particle at a detector is modeled by an absorbing term added to
the Hamiltonian. In this well-known scheme the probability for the particle's
arrival at the counter is identified with the loss of normalization for an
initial wave packet. Under the sole assumption that the absorbing term vanishes
on the initial wave function, we show that and , where denotes the mean
arrival time, and is the probability for the particle to be eventually
absorbed. Nearly minimal uncertainty can be achieved in a two-level system, and
we propose a trapped ion experiment to realize this situation.Comment: 8 pages, 2 figure
Measurement uncertainty relations
Measurement uncertainty relations are quantitative bounds on the errors in an
approximate joint measurement of two observables. They can be seen as a
generalization of the error/disturbance tradeoff first discussed heuristically
by Heisenberg. Here we prove such relations for the case of two canonically
conjugate observables like position and momentum, and establish a close
connection with the more familiar preparation uncertainty relations
constraining the sharpness of the distributions of the two observables in the
same state. Both sets of relations are generalized to means of order
rather than the usual quadratic means, and we show that the optimal constants
are the same for preparation and for measurement uncertainty. The constants are
determined numerically and compared with some bounds in the literature. In both
cases the near-saturation of the inequalities entails that the state (resp.
observable) is uniformly close to a minimizing one.Comment: This version 2 contains minor corrections and reformulation
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