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Search Results: 1 - 10 of 149820 matches for " H. Fearn "
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Mach’s Principle, Action at a Distance and Cosmology  [PDF]
H. Fearn
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.63031
Abstract: Hoyle and Narlikar (HN) in the 1960’s [1]-[3] developed a theory of gravitation which was completely Machian and used both retarded and advanced waves to communicate gravitational influence between particles. The advanced waves, which travel backward in time, are difficult to visualize and although they are mathematically allowed by relativistic wave equations, they never really caught on. The HN theory reduced to Einstein’s theory of gravity in the smooth fluid approximation and a transformation into the rest frame of the fluid. Hawking [4] in 1965 pointed out a possible flaw in the theory. This involved integrating out into the distant future to account for all the advanced waves which might influence the mass of a particle here and now. Hawking used infinity as his upper time limit and showed the integral was divergent. We point out that since the universe is known to be expanding, and accelerating, the upper limit in the advanced wave time integral should not be infinite but is bounded by the Cosmic Event Horizon. This event horizon He represents a barrier between future events that can be observed and those which cannot. We show that the advanced wave integral is finite when He/C, is used as the upper limit of the advanced wave integral. Hawking’s objection is no longer valid and the HN theory becomes a working theory once again.
On radiation reaction and the [x,p ] commutator for an accelerating charge
H. Fearn
Physics , 2013,
Abstract: We formally state the connection between the relativistic part of the radiation reaction and the Poynting Robertson force term, $-Rv/c^2$, where $R$ is power radiated. Then we address the question, does $[x,p]=i \hb$ for an accelerating charge ? The full radiation reaction term is used, which includes the relativistic term (von Laue vector.). We show that the full relativistic radiation reaction term must be taken into account if a commutation relation between $x$ and $p$ is to hold for an electron under uniform acceleration, consistent with the expectation values of $x^2$ and $p^2$.
Radiation Reaction Force on a Particle
H. Fearn,J. Bengtsson
Physics , 2012,
Abstract: The Abrahamn Lorentz radiation reaction force term, with da/dt, derived in text books is shown to be incomplete. We show that, with the addition of a term, the classical radiation reaction force can be generalized to the relativistic force expression. This addition is the Poynting Robertson term, seen mostly in astrophysics and usually missing from texts in electromagnetism. With this term added, it takes into account the rate of change of mass dm/dt of the particle and makes the generalization to the relativisitic formula for force very straight forward.
Dispersion Relations and Relativistic Causality
H. Fearn,R. H. Gibb
Physics , 2003,
Abstract: In this paper we show that if the refractive index, or rather (n(w) -1) satisfies the dispersion relations then, it is implied by Titchmarsh's theorem that n(w) -> 1 as w -> infinity. Any other limiting value for n(w) would violate relativistic causality, by which we mean not only that cause must precede effect but also that signals cannot travel faster-than-c (the velocity of light) in a vacuum. This paper does not claim to be a mathematically rigorous proof, but the authors hope to have succeeded in supplying a very convincing argument against faster-than-c light signals. Keywords: Dispersion relations, Kramers Kronig relations, Causality, faster-than-c signals.
Singlet-triplet filtering and entanglement in a quantum dot structure
G. Giavaras,J. H. Jefferson,M. Fearn,C. J. Lambert
Physics , 2006, DOI: 10.1103/PhysRevB.75.085302
Abstract: We consider two interacting electrons in a semiconductor quantum dot structure which consists of a small dot within a larger dot, and demonstrate a singlet-triplet filtering mechanism which involves spin-dependent resonances and can generate entanglement. By studying the exact time evolution of singlet and triplet states we show how the degree of both filtering and spin entanglement can be tuned using a time-dependent gate voltage.
Generation of EPR pairs and interconversion of static and flying electron spin qubits
G. Giavaras,J. H. Jefferson,M. Fearn,C. J. Lambert
Physics , 2007, DOI: 10.1103/PhysRevB.76.245328
Abstract: We propose a method of generating fully entangled electron spin pairs using an open static quantum dot and a moving quantum dot, realized by the propagation of a surface acoustic wave (SAW) along a quasi-one-dimensional channel in a semiconductor heterostructure. In particular, we consider a static dot (SD) loaded with two interacting electrons in a singlet state and demonstrate a mechanism which enables the moving SAW-dot to capture and carry along one of the electrons, hence yielding a fully entangled static-flying pair. We also show how with the same mechanism we can load the SD with one or two electrons which are initially carried by a SAW-induced dot. The feasibility of realizing these ideas with existing semiconductor technology is demonstrated and extended to yield flying or static pairs that are fully entangled and arbitrary interconversion of static and flying electron spin qubits.
Can Light Signals Travel Faster than c in Nontrivial Vacuua in Flat space-time? Relativistic Causality II
Heidi Fearn
Physics , 2007, DOI: 10.1134/S1054660X07050155
Abstract: In this paper we show that the Scharnhorst effect (Vacuum with boundaries or a Casimir type vacuum) cannot be used to generate signals showing measurable faster-than-c speeds. Furthermore, we aim to show that the Scharnhorst effect would violate special relativity, by allowing for a variable speed of light in vacuum, unless one can specify a small invariant length scale. This invariant length scale would be agreed upon by all inertial observers. We hypothesize the approximate scale of the invariant length.
Two-electron quantum dots as scalable qubits
J. H. Jefferson,M. Fearn,D. L. J. Tipton,T. P. Spiller
Physics , 2002, DOI: 10.1103/PhysRevA.66.042328
Abstract: We show that two electrons confined in a square semiconductor quantum dot have two isolated low-lying energy eigenstates, which have the potential to form the basis of scalable computing elements (qubits). Initialisation, one-qubit and two-qubit universal gates, and readout are performed using electrostatic gates and magnetic fields. Two-qubit transformations are performed via the Coulomb interaction between electrons on adjacent dots. Choice of initial states and subsequent asymmetric tuning of the tunnelling energy parameters on adjacent dots control the effect of this interaction.
On the flight of an American Football
Curtis Horn,Heidi Fearn
Physics , 2007,
Abstract: In this paper we examine the detailed theory of the American football in flight, with spin and air resistance included. We find the theory has much in common with the theory of a gyroscope and also rocket trajectory with a misaligned thruster. Unfortunately most of the air resistance data, for rocketry and ballistics, is for speeds of Mach 1 or higher, where the air resistance increases dramatically. We shall approximate a realistic air resistance, at the slower speeds of football flight, with a drag force proportional to cross sectional area and either $v$ or $v^2$, depending on speed, where $v$ is velocity of the football. We begin with a discussion of the motion, giving as much detail as possible without the use of complex analytic calculations. We point out the previous errors made with moments of inertia and make the necessary corrections for more accurate results. We show that the shape of an American football closely resembles a parabola of revolution.
Derivation of the Aharanov Bohm phase shift using classical forces
Heidi Fearn,Khai Nguyen
Physics , 2011,
Abstract: In 1959 Aharonov and Bohm suggested that an electron passing around a long solenoid would pick up a phase shift dependent on the magnetic field of the solenoid, even though the electrons themselves pass through a region of space which has a zero magnetic field. It has long been held that this result is purely quantum and is derived in many well known quantum mechanics text books using the Schrodinger equation and vector potential. Here the same phase shift is derived from a purely classical force, but relativistic transformations are taken into account. The force is in the direction of motion of the electron (or opposite) leading to a phase advance (or lag) and we obtain precisely the phase shift thought previously to be purely quantum. The only quantum result used here is the de Broglie wavelength of the particle, in order to get two slit like interference and the phase shift. We employ a stack of dipoles as the solenoid and note the same force on the electron in two different frames of reference. We shall consider the solenoid stationary and the electron moving, and then consider the electron rest frame and consider the solenoid moving in the opposite direction.
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