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Michael C. Mackey

Publications and source records attributed to Michael C. Mackey.

28 records · Page 2Linked to original sources
arXiv2007

Electromagnetic dark energy

We introduce a new model for dark energy in the universe in which a small cosmological constant is generated by ordinary electromagnetic vacuum energy. The corresponding virtual photons exist at all frequencies but switch from a gravitationally active phase at low frequencies to a gravitationally inactive phase at higher frequencies via a Ginzburg-Landau type of phase transition. Only virtual photons in the gravitationally active state contribute to the cosmological constant. A small vacuum energy density, consistent with astronomical observations, is naturally generated in this model. We propose possible laboratory tests for such a scenario based on phase synchronisation in superconductors.

astro-ph↗
arXiv2006

Rebuttal to: Has dark energy really been discovered in the Lab?

We argue that a recent discussion of Jetzer and Straumann [Phys. Lett. B 606, 77 (2005)] relating the measured noise spectrum in Josephson junctions to van der Waals forces is incorrect. The measured noise spectrum in Josephson junctions is a consequence of the fluctuation dissipation theorem and the Josephson effect and has nothing to do with van der Waals forces. Consequently, the argument of Jetzer and Straumann does not shed any light on whether dark energy can or cannot be measured using superconducting Josephson devices. We also point out that a more recent paper of Jetzer and Straumann [Phys. Lett. B 639, 57 (2006)] claiming that `zeropoint energies do not show up in any application of the fluctuation dissipation theorem' violates the standard view on the subject.

astro-ph↗
arXiv2006

Measurability of vacuum fluctuations and dark energy

Vacuum fluctuations of the electromagnetic field induce current fluctuations in resistively shunted Josephson junctions that are measurable in terms of a physical power spectrum. In this paper we investigate under which conditions vacuum fluctuations can be gravitationally active, thus contributing to the dark energy density of the universe. Our central hypothesis is that vacuum fluctuations are gravitationally active if and only if they are measurable in terms of a physical power spectrum in a suitable macroscopic or mesoscopic detector. This hypothesis is consistent with the observed dark energy density in the universe and offers a resolution of the cosmological constant problem. Using this hypothesis we show that the observable vacuum energy density rho_vac in the universe is related to the largest possible critical temperature T_c of superconductors through rho_vac = sigma (kT_c)^4/(hbar^3 c^3), where sigma is a small constant of the order 10^-3. This relation can be regarded as an analog of the Stefan-Boltzmann law for dark energy. Our hypothesis is testable in Josephson junctions where we predict there should be a cutoff in the measured spectrum at 1.7 THz if the hypothesis is true.

astro-ph↗
arXiv2005

Temporal Behavior of the Conditional and Gibbs' Entropies

We study the temporal approach to equilibrium of the Gibbs' and conditional entropies for both invertible deterministic dynamics as well as non-invertible stochastic systems in the presence of white noise. The conditional entropy will either remain constant or monotonically increase to its maximum of zero. However, the Gibbs' entropy may have a variety of patterns of approach to its final value ranging from a monotone increase or decrease to an oscillatory approach. We have illustrated all of these behaviors using examples in which both entropy dynamics can be determined analytically.

cond-mat.stat-mech↗
arXiv2005

Effects of Noise on Entropy Evolution

We study the convergence properties of the conditional (Kullback-Leibler) entropy in stochastic systems. We have proved very general results showing that asymptotic stability is a necessary and sufficient condition for the monotone convergence of the conditional entropy to its maximal value of zero. Additionally we have made specific calculations of the rate of convergence of this entropy to zero in a one-dimensional situations, illustrated by Ornstein-Uhlenbeck and Rayleigh processes, higher dimensional situations, and a two dimensional Ornstein-Uhlenbeck process with a stochastically perturbed harmonic oscillator and colored noise as examples. We also apply our general results to the problem of conditional entropy convergence in the presence of dichotomous noise. In both the single dimensional and multidimensional cases we are to show that the convergence of the conditional entropy to zero is monotone and at least exponential. In the specific cases of the Ornstein-Uhlenbeck and Rayleigh processes as well as the stochastically perturbed harmonic oscillator and colored noise examples, we have the rather surprising result that the rate of convergence of the entropy to zero is independent of the noise amplitude.

cond-mat.stat-mech↗
arXiv2004

Could dark energy be measured in the lab?

The experimentally measured spectral density of current noise in Josephson junctions provides direct evidence for the existence of zero-point fluctuations. Assuming that the total vacuum energy associated with these fluctuations cannot exceed the presently measured dark energy of the universe, we predict an upper cutoff frequency of nu_c=(1.69 +- 0.05) x 10^12 Hz for the measured frequency spectrum of zero-point fluctuations in the Josephson junction. The largest frequencies that have been reached in the experiments are of the same order of magnitude as nu_c and provide a lower bound on the dark energy density of the universe. It is shown that suppressed zero-point fluctuations above a given cutoff frequency can lead to 1/f noise. We propose an experiment which may help to measure some of the properties of dark energy in the lab.

astro-ph↗
arXiv2004

Periodic Oscillations of Blood Cell Populations in Chronic Myelogenous Leukemia

We develop some techniques to prove analytically the existence and stability of long period oscillations of stem cell populations in the case of periodic chronic myelogenous leukemia. Such a periodic oscillation $p_\infty $ can be analytically constructed when the hill coefficient involved in the nonlinear feedback is infinite, and we show it is possible to obtain a contractive returning map (for the semiflow defined by the modeling functional differential equation) in a closed and convex cone containing $p_\infty $ when the hill coefficient is large, and the fixed point of such a contractive map gives the long period oscillation previously observed both numerically and experimentally.

q-bio.TO↗
arXiv2004

Oscillations in a maturation model of blood cell production

In this paper we use a continuous model to describe the development of a single cell lineage following the committal of stem cells. Three separate controls are implemented in the model, namely the proliferative control of stem cells, the proliferative control of developing blast cells, and the peripheral control of stem cell committal by circulating blood cell density. We show that variation of parameters in all three control systems can cause oscillations, and that the characters of these oscillations are very different. This allows us some potential insight into the mechanisms that may be operative in some of the dynamic blood diseases like cyclical neutropenia and periodic chronic myelogenous leukemia.

q-bio.TO↗
arXiv2004

Deterministic Brownian Motion: The Effects of Perturbing a Dynamical System by a Chaotic Semi-Dynamical System

Here we review and extend central limit theorems for highly chaotic but deterministic semi-dynamical discrete time systems. We then apply these results show how Brownian motion-like results are recovered, and how an Ornstein-Uhlenbeck process results within a totally deterministic framework. These results illustrate that the contamination of experimental data by "noise" may, under certain circumstances, be alternately interpreted as the signature of an underlying chaotic process.

cond-mat.stat-mech↗