A five-dimensional model of varying fine structure constant

The cosmological variation of the fine structure constant α is explored from an effective theory, under the form of an improved version of the 5D Kaluza-Klein theory.     

On the fine structure constant

In the framework of a particle model based on a classical minimum action principle a number α′ is derived which is shown to be the analogue of the fine structure constant $\text{α = e}{}^2\text{/}\text{h}\text{?}\text{c}$. To compute α′, a pair of coupled partial differential equations of the second order must be solved. No exact result has been obtained as yet, but it is likely that α′ ? 1. The analogy between α′ and α opens a clear insight into the meaning of the fine structure constant.     

Phase transition in the fine structure constant

Within the context of mass-varying neutrinos, we construct a cosmological model that has a phase transition in the electromagnetic fine structure constant at a redshift of 0.5. The model accommodates hints of a time variable in quasar spectra and the nonobservance of such an effect at very low redshifts. It is consistent with limits from the recombination and primordial nucleosynthesis eras and is free of instabilities.     

The Casimir effect and the fine structure constant

We consider the electron as a charged sphere that completely absorbs any radiation with wave number less than somek _m . The Casimir effect then provides a self stress which can balance the mutual repulsion of the distinct parts of the finite charge distribution. From this equilibrium condition and connecting, by quantum arguments, the value ofk _m to the radius of the electron, we obtain a good estimate for the value of the fine-structure constant.     

Topological quantization in units of the fine structure constant

Fundamental topological phenomena in condensed matter physics are associated with a quantized electromagnetic response in units of fundamental constants. Recently, it has been predicted theoretically that the time-reversal invariant topological insulator in three dimensions exhibits a topological magnetoelectric effect quantized in units of the fine structure constant α=e2/?c. In this Letter, we propose an optical experiment to directly measure this topological quantization phenomenon, independent of material details. Our proposal also provides a way to measure the half-quantized Hall conductances on the two surfaces of the topological insulator independently of each other.     

Renormalization of the fine structure constant at high energies

Continuing the discussion in [1], the renormalization of the fine-structure constant in the high-energy range, where a logarithmic increase in the constant is observed, is considered. It is shown that within the framework of the quantum electrodynamics of bilocal fields, when the energy increases the logarithmic "form" ln² of the constant changes into a power drop 1/². Hence, problems with the "Moscow zero" do not arise in this theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 3–12, January, 1996.     

Cosmological constant and quantum gravitational corrections to the running fine structure constant

The quantum gravitational contribution to the renormalization group behavior of the electric charge in Einstein-Maxwell theory with a cosmological constant is considered. Quantum gravity is shown to lead to a contribution to the running charge not present when the cosmological constant vanishes. This reopens the possibility, suggested by Robinson and Wilczek, of altering the scaling behavior of gauge theories at high energies although our result differs. We show the possibility of an ultraviolet fixed point that is linked directly to the cosmological constant.     

Indications of a spatial variation of the fine structure constant

We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant α at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; α increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the 4.2 σ level, in the direction right ascension 17.5 ± 0.9 h, declination -58 ± 9 deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.     

An estimation of the fine structure constant using fiber bundles

We calculateg ₀/e whereg ₀ is the strength of an elementary magnetic monopole ande the charge on the electron, in terms of a ratio of loop sizes in the twisted and untwisted principal fiber bundles withU(1) the structure group andR ³-{0} the base space. The result involves the present distance around theU(1) space and, rather surprisingly, the structure of the quantum gravitational vacuum. Combining our result with the expression foreg ₀ from the Dirac quantization condition gives a final estimate for the fine structure constant,1/100.     

Further evidence for cosmological evolution of the fine structure constant

We describe the results of a search for time variability of the fine structure constant alpha using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm and mm absorption systems provide four independent samples, spanning approximately 23% to 87% of the age of the universe. Each sample yields a smaller alpha in the past and the optical sample shows a 4 sigma deviation: Delta alpha/alpha = -0.72+/-0.18 x 10(-5) over the redshift range 0.5相似文献   

Search for a possible variation of the fine structure constant

The determination of the fine structure constant α and the search for its possible variation are considered. We focus on the role of the fine structure constant in modern physics and discuss precision tests of quantum electrodynamics.Different methods of a search for possible variations of fundamental constants are compared and those related to optical measurements are considered in detail.     

Limit on the present temporal variation of the fine structure constant

The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in 171Yb+ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio f(Yb)/f(Cs) of (-1.2+/-4.4)x10(-15) yr(-1), consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of alpha at the level of 2.0x10(-15) yr(-1) (1sigma), corresponding so far to the most stringent limit from laboratory experiments.     

Mach's principle,mass, and the fine structure constant

A modified form of Mach's principle is proposed, and its consequences are discussed.Work supported in part by the U.S. Atomic Energy Commission.     

A new photon recoil experiment: towards a determination of the fine structure constant

We report on progress towards a measurement of the fine structure constant α to an accuracy of 5×10^-10 or better by measuring the ratio h/m_Cs of the Planck constant h to the mass of the cesium atom m_Cs. Compared to similar experiments, ours is improved in three significant ways: (i) simultaneous conjugate interferometers, (ii) multi-photon Bragg diffraction between same internal states, and (iii) an about 1000-fold reduction of laser phase noise to -138 dBc/Hz. Combining that with a new method to simultaneously stabilize the phases of four frequencies, we achieve 0.2 mrad effective phase noise at the location of the atoms. In addition, we use active stabilization to suppress systematic effects due to beam misalignment. PACS 03.75.Dg; 06.20.Jr; 06.30.Ft; 39.20.+q; 03.65.Ta     

Cold molecule spectroscopy for constraining the evolution of the fine structure constant

We report precise measurements of ground-state, Lambda-doublet microwave transitions in the hydroxyl radical molecule (OH). Utilizing slow, cold molecules produced by a Stark decelerator we have improved over the precision of the previous best measurement 25-fold for the F'=2-->F=2 transition, yielding (1 667 358 996 +/- 4)Hz, and by tenfold for the F'=1-->F=1 transition, yielding (1 665 401 803 +/-12)Hz. Comparing these laboratory frequencies to those from OH megamasers in interstellar space will allow a sensitivity of 1 ppm for Delta(alpha/alpha) over approximately 10(10) yr.     

New measurement of the electron magnetic moment and the fine structure constant

A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, g/2=1.001 159 652 180 73 (28) [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow line shape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with alpha{-1}=137.035 999 084 (51) [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of alpha.