The noise in gravitational-wave detectors and other classical-force measurements is not influenced by test-mass quantization

It is shown that photon shot noise and radiation-pressure back-action noise are the sole forms of quantum noise in interferometric gravitational wave detectors that operate near or below the standard quantum limit, if one filters the interferometer output appropriately. No additional noise arises from the test masses' initial quantum state or from reduction of the test-mass state due to measurement of the interferometer output or from the uncertainty principle associated with the test-mass state. Two features of interferometers are central to these conclusions: (i) The interferometer output (the photon number flux N(t) entering the final photodetector) commutes with itself at different times in the Heisenberg Picture, [N(t), N(t')] = 0, and thus can be regarded as classical. (ii) This number flux is linear in the test-mass initial position and momentum operators x_o and p_o, and those operators influence the measured photon flux N(t) in manners that can easily be removed by filtering -- e.g., in most interferometers, by discarding data near the test masses' 1 Hz swinging freqency. The test-mass operators x_o and p_o contained in the unfiltered output N(t) make a nonzero contribution to the commutator [N(t), N(t')]. That contribution is cancelled by a nonzero commutation of the photon shot noise and radiation-pressure noise, which also are contained in N(t). This cancellation of commutators is responsible for the fact that it is possible to derive an interferometer's standard quantum limit from test-mass considerations, and independently from photon-noise considerations. These conclusions are true for a far wider class of measurements than just gravitational-wave interferometers. To elucidate them, this paper presents a series of idealized thought experiments that are free from the complexities of real measuring systems.Comment: Submitted to Physical Review D; Revtex, no figures, prints to 14 pages. Second Revision 1 December 2002: minor rewording for clarity, especially in Sec. II.B.3; new footnote 3 and passages before Eq. (2.35) and at end of Sec. III.B.

Ruled Laguerre minimal surfaces

A Laguerre minimal surface is an immersed surface in the Euclidean space being an extremal of the functional \int (H^2/K - 1) dA. In the present paper, we prove that the only ruled Laguerre minimal surfaces are up to isometry the surfaces R(u,v) = (Au, Bu, Cu + D cos 2u) + v (sin u, cos u, 0), where A, B, C, D are fixed real numbers. To achieve invariance under Laguerre transformations, we also derive all Laguerre minimal surfaces that are enveloped by a family of cones. The methodology is based on the isotropic model of Laguerre geometry. In this model a Laguerre minimal surface enveloped by a family of cones corresponds to a graph of a biharmonic function carrying a family of isotropic circles. We classify such functions by showing that the top view of the family of circles is a pencil.Comment: 28 pages, 9 figures. Minor correction: missed assumption (*) added to Propositions 1-2 and Theorem 2, missed case (nested circles having nonempty envelope) added in the proof of Pencil Theorem 4, missed proof that the arcs cut off by the envelope are disjoint added in the proof of Lemma

Computation of the winding number diffusion rate due to the cosmological sphaleron

A detailed quantitative analysis of the transition process mediated by a sphaleron type non-Abelian gauge field configuration in a static Einstein universe is carried out. By examining spectra of the fluctuation operators and applying the zeta function regularization scheme, a closed analytical expression for the transition rate at the one-loop level is derived. This is a unique example of an exact solution for a sphaleron model in $3+1$ spacetime dimensions.Comment: Some style corrections suggested by the referee are introduced (mainly in Sec.II), one reference added. To appear in Phys.Rev.D 29 pages, LaTeX, 3 Postscript figures, uses epsf.st

Modeling the actinides with disordered local moments

A first-principles disordered local moment (DLM) picture within the local-spin-density and coherent potential approximations (LSDA+CPA) of the actinides is presented. The parameter free theory gives an accurate description of bond lengths and bulk modulus. The case of $\delta$-Pu is studied in particular and the calculated density of states is compared to data from photo-electron spectroscopy. The relation between the DLM description, the dynamical mean field approach and spin-polarized magnetically ordered modeling is discussed.Comment: 6 pages, 4 figure

Counting Domain Walls in N=1 Super Yang-Mills Theory

We study the multiplicity of BPS domain walls in N=1 super Yang-Mills theory, by passing to a weakly coupled Higgs phase through the addition of fundamental matter. The number of domain walls connecting two specified vacuum states is then determined via the Witten index of the induced worldvolume theory, which is invariant under the deformation to the Higgs phase. The worldvolume theory is a sigma model with a Grassmanian target space which arises as the coset associated with the global symmetries broken by the wall solution. Imposing a suitable infrared regulator, the result is found to agree with recent work of Acharya and Vafa in which the walls were realized as wrapped D4-branes in IIA string theory.Comment: 28 pages, RevTeX, 3 figures; v2: discussion of the index slightly expanded, using an alternative regulator, and references added; v3: typos corrected, to appear in Phys. Rev.

Experimentally verified modeling of erbium-ytterbium co-doped DFB lasers

For the first time, the simulation results of fiber distributed feedback (DFB) lasers are compared against experimental data in this paper. The pump source, active medium, and grating are all modeled and simulated to predict actual laser characteristics. Simple characterization methods are illustrated for the measurement of model parameters. Large loss at the pump wavelength is observed, attributed to the lifetime quenching of Yb ions, and included in the model as a critical parameter. DFB lasers with two different apodization profiles successfully simulated with the same set of model parameters

Measuring the Extent of Structural Remedy in Section 7 Settlements: Was the US DOJ Successful in the 1990s?

This paper suggests an innovative measure of structural relief obtained in a typical Section 7 settlement. The fraction of competitive overlap subject to divestiture as a condition of the settlement is modeled as a function of merger-specific efficiencies, the proportion of the deal held “hostage” to antitrust review, the merger’s anticompetitive potential, and other factors. The model is applied to data on 86 recent Justice Department cases covering the period 1990–2003 and to the subsample of 1990s cases. All data are collected from publicly available documents only. The government is found to secure larger divestitures when the cost to the acquirer of delaying the settlement is high. The resulting estimates are used to predict several out-of-sample observations. Copyright Springer Science+Business Media, LLC 2007merger policy, U.S. Department of Justice, structural remedies, L44, C24,

400mW 1060nm ytterbium doped fiber DFB laser

We report for the first time, more than 400mW of output power at 1056.1nm from a distributed feedback (DFB) fiber laser. The DFB fiber laser comprises a simple pi-phase-shifted Bragg grating written into a photosensitive ytterbium-doped fiber. The laser operates with a single longitudinal mode at a wavelength defined by the phase shift and the grating period. Without any internal polarisation selection mechanism, the cavity supports orthogonal polarisation modes, which operate simultaneously. The DFB fiber laser was pumped by a 976nm amplified spontaneous emission (ASE) source based on a ytterbium doped jacketed air clad (JAC) fiber pumped by a 915nm multimode laser diode source. An output of 400mW at 1056.1nm was obtained from the output port while 70mW was obtained from the other port, when pumped with 1.5W of 976nm radiation. The total output from the DFB fiber laser was approximately linear with increasing pump power and the overall performance was limited by the available pump power. The spectral characteristics and signal to noise ratio remained similar over the pump power range. The output of the DFB was in single-mode fiber (ie. M2~1)