* Astronomy

Blobrana · L

RE: Fine structure constant

Blobrana · L

Title: Fine Structure Constant, Domain Walls, and Generalized Uncertainty Principle in the Universe
Authors: Luigi Tedesco

We study the corrections to the fine-structure constant from the generalized uncertainty principle in the spacetime of a domain wall. We also calculate the corrections to the standard formula to the energy of the electron in the hydrogen atom to the ground state, in the case of spacetime of a domain wall and generalized uncertainty principle. The results generalize the cases known in literature.

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Blobrana · L

Title: f(T) Theories and Varying Fine Structure Constant
Authors: Hao Wei, Xiao-Peng Ma, Hao-Yu Qi

In analogy to f(R) theory, recently f(T) theory has been proposed to drive the current accelerated expansion without invoking dark energy. In the literature, the observational constraints on f(T) theories were obtained mainly by using the cosmological data, such as type Ia supernovae (SNIa), baryon acoustic oscillation (BAO), and cosmic microwave background radiation (CMB). In this work, we instead try to constrain f(T) theories with the varying fine structure "constant", \alpha\equiv e^2/\hbar c. We find that the constraints on f(T) theories from the observational \Delta\alpha/\alpha data are very severe. In fact, they make f(T) theories almost indistinguishable from \Lambda CDM model.

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Blobrana · L

Title: Constraining Variations in the Fine Structure Constant in the presence of Early Dark Energy
Authors: Erminia Calabrese, Eloisa Menegoni, C.J.A.P. Martins, Alessandro Melchiorri, Graca Rocha

We discuss present and future cosmological constraints on variations of the fine structure constant $\alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with \alpha / \alpha_0 = 0.975 ±0.020 at 95 % c.l., constraining the energy density in early dark energy to \Omega_e < 0.060 at 95 % c.l.. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as Planck Surveyor and CMBPol, can match and possibly even surpass the sensitivity of current local tests.

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Blobrana · L

Title: Runaway Domain Wall and Space-time Varying alpha
Authors: Takeshi Chiba, Masahide Yamaguchi

Recently spatial as well as temporal variations of the fine structure constant alpha have been reported. We show that a "runaway domain wall", which arises for the scalar field potential without minima, can account for such variations simultaneously. The time variation is induced by a runaway potential and the spatial variation is induced by the formation of a domain wall. The model is consistent with the current cosmological data and can be tested by the future experiments to test the equivalence principle.

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Blobrana · L

Are there no universal laws?

It looks like physics works differently in different places. If so, everything we think we know about the cosmos may be wrong
It's not easy being John Webb. Sometimes, when he gives a talk about his work, he gets comments like, "I'm surprised you had the guts to say that."
Webb, who is an astronomer, doesn't really understand what else he is supposed to do.
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Blobrana · L

Distant gas blob threatens to shake nature's constants

The basic constants of nature aren't called constants for nothing. Physics is supposed to work the same way across the universe and over all of time. Now measurements of the radio spectra of a distant gas cloud hint that some fundamental quantities might not be fixed after all, raising the possibility that a radical rethink of the standard model of particle physics may one day be needed.
The evidence comes from observations of a dense gas cloud some 2.9 billion light years away which has a radio source, the active supermassive black hole PKS 1413+135, right behind it. Hydroxyl radicals in the gas cloud absorb the galaxy's radio energy at certain wavelengths and emit it again at different wavelengths. This results in so-called "conjugate" features in the radio spectrum of the gas, with a dip in intensity corresponding to absorption and an accompanying spike corresponding to emission.
The dip and spike have the same shape, which shows that they arise from the same gas. But Nissim Kanekar of the National Centre for Radio Astrophysics in Pune, India, and colleagues found that the gap in frequency between the two was smaller than the properties of hydroxyl radicals would lead us to expect.
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Blobrana · L

Title: Probing fundamental constant evolution with redshifted conjugate-satellite OH lines
Authors: Nissim Kanekar (1,2), Jayaram N. Chengalur (1), Tapasi Ghosh (3) ((1) National Centre for Radio Astrophysics, India, (2) National Radio Astronomy Observatory, USA, (3) Arecibo Observatory, USA)

We report Westerbork Synthesis Radio Telescope and Arecibo Telescope observations of the redshifted satellite OH-18cm lines at z ~ 0.247 towards PKS1413+135. The "conjugate" nature of these lines, with one line in emission and the other in absorption, but with the same shape, implies that the lines arise in the same gas. The satellite OH-18cm line frequencies also have different dependences on the fine structure constant \alpha, the proton-electron mass ratio \mu = m_p/m_e, and the proton gyromagnetic ratio g_p. Comparisons between the satellite line redshifts in conjugate systems can hence be used to probe changes in \alpha, \mu, and g_p, with few systematic effects. The technique yields the expected null result when applied to Cen.A, a nearby conjugate satellite system. For the z ~ 0.247 system towards PKS1413+135, we find, on combining results from the two telescopes, that [\Delta G/G] = (-1.18 ±0.46) x 10^{-5} (weighted mean), where G = g_p [\mu \alpha²]^{1.85}; this is tentative evidence (with 2.6 \sigma significance, or at 99.1% confidence) for a smaller value of \alpha, \mu, and/or g_p at z~0.247, i.e. at a lookback time of ~2.9 Gyrs. If we assume that the dominant change is in \alpha, this implies [\Delta \alpha /\alpha ] = (-3.1 ±1.2) x 10^{-6}. We find no evidence that the observed offset might be produced by systematic effects, either due to observational or analysis procedures, or local conditions in the molecular cloud.

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Blobrana · L

Six times Nine, in the base thirteen, equals FortyTwo.
Pi is one such number that seems to be beyond our grasp of knowing. But in a universe (if it could exist) that Pi was a computable or whole number, like Three or 3.5, how would reality seem?
Space would be curved! The circumference of a circle would be devisable exactly by it`s radius.
Conversely,(ho ho) in our universe we could find out how flat space is, by looking at how theoretical Pi differs from observed/measured Pi.
If the universe is very, very flat it will expand forever.

1/137.036, is the fine structure constant.

The fine structure constant can be seen at many places. For example, the (squared) speed of electrons in the hydrogen atom is roughly 1/137 of the (squared) speed of light. As a consequence of this, the spectrum of the hydrogen atoms have the famous lines with energies 1/n2, but if you look at the lines with a better resolution, you find out that they are separated to several sublines; they form the so-called fine structure of the Hydrogen spectrum.
The distance between the main lines of the spectrum is 137 times bigger than the distance between the lines in the fine structure; therefore the name.
If 137 was replaced by 10, the spectrum would look completely different, most known nuclei would decay radioactively...
(because proton repel each other electromagnetically and this force would be stronger than the extra "chromostatic" attraction between quarks - in our world, the electromagnetism is weaker and the attraction by gluons wins).

Simply, it would be a very different universe.

Solid lines are charged fermions electrons or positrons (spinor wavefunctions) Wavy (or dashed) lines are photons Arrow on solid line signifies e- or e+ e- arrow in same direction as time e+ arrow opposite direction as time	E = m (not m * c² since we're normalizing c = 1) E = omega (not hBaromega for the same reason) F = m1m2 / r²** (not Gm1m2 / r²) and *F = q1q2 / r²** (not kq1q2 / r²) The unit charge is not e but would be e/sqrt(alpha)
	At each vertex there is a coupling constant a, a= 1/137=fine structure constant All quantum numbers are conserved at vertex e.g. electric charge, lepton number "Virtual" Particles do not conserve E, p

Blobrana · L

Title: Constraints on the time variation of the fine structure constant by the 5-year WMAP data
Authors: Masahiro Nakashima, Ryo Nagata, Jun'ichi Yokoyama

The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, \Delta\alpha/\alpha \equiv (\alpha_{\mathrm{rec}} - \alpha_{\mathrm{now}})/\alpha_{\mathrm{now}}, are obtained from the analysis of the 5-year WMAP cosmic microwave background data. As a result of Markov-Chain Monte-Carlo analysis, it is found that, contrary to the analysis based on the previous WMAP data, the mean value of \Delta\alpha/\alpha=-0.0009 does not change significantly whether we use the Hubble Space Telescope (HST) measurement of the Hubble parameter as a prior or not. The resultant 95% confidence ranges of \Delta\alpha/\alpha are -0.028 < \Delta\alpha/\alpha < 0.026 with HST prior and -0.050 < \Delta\alpha/\alpha < 0.042 without HST prior.

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