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Cosmic Variation of the Fine Structure Constant

Does the fine-structure constant vary with cosmological epoch? John Bahcall, Charles Steinhardt, and David Schlegel astroph/0301507 Sept. 24, 2003 The Chemical Evolution of Mg Isotopes, vs. the Time Variation of the Fine Structure Constant T. Ashenfelter, Grant Mathews and Keith Olive astroph/0309197 Sept. 8, 2003 also see Jean-Philippe Uzan: The fundamental constants and their variation: observational and theoretical status Review of Modern Physics, 75, 403. April 2003

Background

●

Copernican principle: we are not living in a particular place in the Universe; the laws of physics do not differ with place or time

●

Fine-structure constant

: a = e

/

hc = 1/137

determines the strength of the electromagnetic interaction

Limits on the time dependence the fine structure constant: astronomical

●

Savedoff (1956)

– splitting of N II and Ne III emission lines of Cynus A ● ●

Bahcall & Salpeter (1965)

Ne III in quasars splitting of O III and

Bahcall, Sargent & Schmidt (1967)

– wavelengths in quasar absorption spectra doublet ● Recent:

Webb and collaborators

, Dzuba, Flambaum & Webb (1999); Murphy, Webb & Flambaum (2003): Mg II splittings,

Many Multiplet method

(quasar absorbers)

Geological Evidence: The Oklo Phenomenon

● ● ● ● Discovered in 1972, in the

Oklo uranium mine in Gabon

, where 235 U is .368% of total, compared to .72% today elsewhere (most uranium is 238 U)

Natural fission reactor

: about 2 billion years ago (or z=0.14; known from radioactive dating of other elements) natural conditions enabled water to slow down fast neutrons so they could could create 235 U by 238 U capture of neutrons The reaction would stop if the water moderator became hot and boiled, but it was at very high pressure so T(boiling)=300 C.

Analysis of Samarium isotopes (e.g. Damour & Dyson 1996) --> Da/ a < 1.8E-8

Quasar Absorbers: doublets and variation in

a ● Dzuba, Flambaum & Webb (1999, Phys Rev A 59, 230)... ● Murphy, Webb & Flambaum (2003 astroph/ 0306483) Use Keck/HIRES spectra of MgII doublet and other multiplets

--> 4.7 sigma result

Da/ a = ( 0.543 +/ 0.116) E -5

and

is a function of cosmic time

Objections

● ● ●

Instrumental

(all HIRES; all Th-Ar)

Line blending

; misidentifications; unknown interlopers from other ● redshifts

Full disclosure

(cf Bahcall+ 2003) When first discovered by Webb and collaborators,

no theory

but now see many papers, e.g. Mota & Barrow astroph/0309273

Grand Unification Theories; Extra-dimensions; Quintessence

etc.

'...

there are important consequences for our understanding of the forces of nature at low energies as well as for the question of the links between couplings in higher dimensions and the three-dimensional shadows that we observe. Any slow change in the scale of the extra dimensions would be revealed by measurable changes in our four-dimensional 'constants

' '.

●

Isotopic Effects

if non-solar isotopic ratios, then don't need time varying fine structure constant

Ashenfelter, Mathews & Olive (2003)

: Higher abundance of 25,26 Mg II relative to 24 Mg II expected from galactic chemical evolution models; seen in metal-poor stars Heavy isotopes of Mg produced by thermal pulsing AGB phase of intermediate mass stars QSO absorber result Solid: AGB production of heavy isotopes dashed: no AGB or bursting intermediate mass stars

Question

: what about isotope ratios of other elements?

Stay tuned

Best test: find same result in a different way Bahcall, Steinhardt & Schlegel (2003)

● Use [O III] narrow emission lines in SDSS Early Release data for quasars ● Expect emission line ratio 5007/4959 = 3; find 2.99 +/0.02

Ratio of 5007/4959

● Long discussion of choice of sample, subsamples, line fitting details ● bootstrap statistics ● 'full disclosure' of data

--> Da/ a = (0.7 +/ 1.4) E-4

compared to qso absorbers:

Da/ a = (-0.543 +/ 0.116) E -5 No time dependence, but can't rule out quasar absorber results