282 research outputs found
Work and energy in inertial and non inertial reference frames
It is usual in introductory courses of mechanics to develop the work and
energy formalism from Newton's laws. On the other hand, literature analyzes the
way in which forces transform under a change of reference frame.
Notwithstanding, no analogous study is done for the way in which work and
energy transform under those changes of reference frames. We analyze the
behavior of energy and work under such transformations and show explicitly the
expected invariance of the formalism under Galilean transformations for one
particle and a system of particles. The case of non inertial systems is also
analyzed and the fictitious works are characterized. In particular, we show
that the total fictitious work in the center of mass system vanishes even if
the center of mass defines a non inertial frame. Finally, some subtleties that
arise from the formalism are illustrated by examples.Comment: 4 pages, 2 figures. LaTeX2e. Part of the approach has been changed
but results are unaltered. Version to appear im American Journal of Physic
Recurrences Associated with a Classical Orbit in the Node of a Quantum Wave Function
Absorption spectra of atoms in magnetic fields reveal recurrences: manifestations of classical orbits (or quantum wave packets) that go out from the atom and later return. A formula from closed-orbit theory asserts that if the orbit lies on a node of the outgoing wave function, then the strength of the recurrence is zero. New quantum calculations, however, show that the recurrence strength is nonzero, though small. We derive a semiclassical formula for the recurrence strength associated with a classical orbit at a node of the quantum wave function. This formula is compared to the quantum mechanical calculation. Compared to other orbits, the recurrence is about 100 times weaker, and obeys a different classical scaling law
Simple Pendulum Revisited
We describe a 8085 microprocessor interface developed to make reliable time
period measurements. The time period of each oscillation of a simple pendulum
was measured using this interface. The variation of the time period with
increasing oscillation was studied for the simple harmonic motion (SHM) and for
large angle initial displacements (non-SHM). The results underlines the
importance of the precautions which the students are asked to take while
performing the pendulum experiment.Comment: 17 pages with 10 figure
Moments of inertia for solids of revolution and variational methods
We present some formulae for the moments of inertia of homogeneous solids of
revolution in terms of the functions that generate the solids. The development
of these expressions exploits the cylindrical symmetry of these objects, and
avoids the explicit use of multiple integration, providing an easy and
pedagogical approach. The explicit use of the functions that generate the solid
gives the possibility of writing the moment of inertia as a functional, which
in turn allows us to utilize the calculus of variations to obtain a new insight
into some properties of this fundamental quantity. In particular, minimization
of moments of inertia under certain restrictions is possible by using
variational methods.Comment: 6 pages, 6 figures, LaTeX2e. Two paragraphs added. Minor typos
corrected. Version to appear in European Journal of Physic
Work and energy in rotating systems
Literature analyzes the way in which Newton's second law can be used when
non-inertial rotating systems are used. However, the treatment of the work and
energy theorem in rotating systems is not considered in textbooks. In this
paper, we show that the work and energy theorem can still be applied to a
closed system of particles in a rotating system, as long as the work of
fictitious forces is properly included in the formalism. The coriolis force
does not contribute to the work coming from fictitious forces. It worths
remarking that real forces that do not do work in an inertial reference frame
can do work in the rotating reference frame and viceversa. The combined effects
of acceleration of the origin and rotation of the non-inertial system are also
studied.Comment: 6 pages, 3 figures, LaTeX2
Atomic Resonance and Scattering
Contains reports on eleven research projects.U.S. Air Force - Office of Scientific Research (Grant AFOSR-81-0067
Crossover from weak to strong coupling regime in dispersive circuit QED
We study the decoherence of a superconducting qubit due to the dispersive
coupling to a damped harmonic oscillator. We go beyond the weak
qubit-oscillator coupling, which we associate with a phase Purcell effect, and
enter into a strong coupling regime, with qualitatively different behavior of
the dephasing rate. We identify and give a physicaly intuitive discussion of
both decoherence mechanisms. Our results can be applied, with small
adaptations, to a large variety of other physical systems, e. g. trapped ions
and cavity QED, boosting theoretical and experimental decoherence studies.Comment: Published versio
Statistics of Oscillator Strengths in Chaotic Systems
The statistical description of oscillator strengths for systems like hydrogen
in a magnetic field is developed by using the supermatrix nonlinear
-model. The correlator of oscillator strengths is found to have a
universal parametric and frequency dependence, and its analytical expression is
given. This universal expression applies to quantum chaotic systems with the
same generality as Wigner-Dyson statistics.Comment: 11 pages, REVTeX3+epsf, two EPS figures. Replaced by the published
version. Minor changes
Testing Lorentz and CPT symmetry with hydrogen masers
We present details from a recent test of Lorentz and CPT symmetry using
hydrogen masers. We have placed a new limit on Lorentz and CPT violation of the
proton in terms of a recent standard model extension by placing a bound on
sidereal variation of the F = 1 Zeeman frequency in hydrogen. Here, the
theoretical standard model extension is reviewed. The operating principles of
the maser and the double resonance technique used to measure the Zeeman
frequency are discussed. The characterization of systematic effects is
described, and the method of data analysis is presented. We compare our result
to other recent experiments, and discuss potential steps to improve our
measurement.Comment: 26 pages, 16 figure
Characterizing the spin state of an atomic ensemble using the magneto-optical resonance method
Quantum information protocols utilizing atomic ensembles require preparation
of a coherent spin state (CSS) of the ensemble as an important starting point.
We investigate the magneto-optical resonance method for characterizing a spin
state of cesium atoms in a paraffin coated vapor cell. Atoms in a constant
magnetic field are subject to an off-resonant laser beam and an RF magnetic
field. The spectrum of the Zeeman sub-levels, in particular the weak quadratic
Zeeman effect, enables us to measure the spin orientation, the number of atoms,
and the transverse spin coherence time. Notably the use of 894nm pumping light
on the D1-line, ensuring the state F=4, m_F=4 to be a dark state, helps us to
achieve spin orientation of better than 98%. Hence we can establish a CSS with
high accuracy which is critical for the analysis of the entangled states of
atoms.Comment: 12 pages ReVTeX, 6 figures, in v2 added ref. and corrected typo
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