Variation in the fine structure constant?: Recent results and the future Michael Murphy, UNSW Project leader: John Webb, UNSW Collaborators: Victor Flambaum, UNSW Vladimir Dzuba, UNSW Chris Churchill, Penn. State Jason Prochaska, OCIW Arthur Wolfe, UCSD John Barrow, Cambridge Francois Combes, Obs. Paris Tommy Wiklind, OSO Wallace Sargent, CalTech Rob Simcoe, CalTech Special thanks to: Anne Thorne, IC Juliet Pickering, IC Richard Learner, IC Ulf Griesmann, NIST Rainer Kling, NIST Sveneric Johansson, Lund U. Ulf Litzén, Lund U. for dedicated laboratory measurements

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Outline:  Motivations for varying constants, particularly the fine structure constant  =e 2 /  c  Previous experimental limits on  variability  Quasar absorption systems and the new, many- multiplet method  Our recent results  Potential systematic effects  A sneak peek at some new preliminary results  Conclusions?

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Motivations for varying constants  1937: Dirac and Milne suggested varying G.  String theory: extra spatial dimensions compactified on tiny scales.  Our (3+1)-dimensional constants related to scale sizes of extra dimensions.  M-theory: gravity acts in all 11 dimensions but other forces (EM, strong, weak) act only in 4-dimensions.  Expect variations in G on small (~0.1mm) scales.  But no variations in coupling constants like  =e 2 /  c.   is most accessible to experimental tests of its constancy.

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Motivations for varying constants:  Varying-speed-of-light (VSL) theories can solve the “cosmological problems”.  Bekenstein (1982) first formulated a varying e theory in which variations in e are driven by spacetime variations of a scalar field.  Sandvik, Barrow & Magueijo (2001) have recast Bekenstein’s theory in terms of a varying c.  Their theory predicts cosmological variations in .

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Previous limits on  /  : Lab. constraints  Different atomic clocks tick with different dependencies on .  The relativistic corrections are of order (Z  ) 2.  Comparison of Hydrogen maser and Hg I clocks yielded  /  1.4× over 140 days (Prestage et al. 1995).

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Previous limits on  /  : The Oklo bound  1972: Discovery of 235 U depletion in a mine in Gabon, Africa (stolen by high-tech terrorists?!).  Explanation: a natural fission reactor operated over 1.8 billion years ago! Zone 15: Natural Uranium Oxide (“yellowcake”)

 Heavy nuclei have very sharp resonances in their neutron absorption cross-section.  Thus, abundances of decay products of 235 U fission give constraints on variation in the nuclear energies and thus a constraint on  / .  1976: Shylakter first analyzed Samarium abundances from Oklo to constrain  / .  1996: Damour & Dyson re-analyzed the same data to obtain a stronger constraint:  /  <1×  2000: Fujii et al. find  /  =(-0.04±0.15)×10 -7 from new data. BUT It is still not clear if these results are meaningful at all! There is much debate over the theory used to obtain  /  from the Samarium abundances. The upper limits on  /  might have to be weakened by a factor of more than 100! This is work in progress. Variation in the fine structure constant?: Recent results and the future Michael Murphy, UNSWUniversity of Canterbury, New Zealand, 17/08/01 Previous limits on  /  : The Oklo bound

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Constraints from QSO absorption lines: To Earth CIV SiIVCIISiII Ly  em Ly  forest Lyman limit Ly  NV em SiIV em Ly  em Ly  SiII Quasar CIV em

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Constraints from QSO absorption lines:  To resolve individual velocity components in a QSO spectrum we need high resolution (FWHM~7 kms -1 ).  Large wavelength coverage  echelle spectrograph.  High SNR  large aperture telescope. Muana Kea (Big Mountain) in Hawaii: cold, high and dry. W. M. Keck telescopes at 14,000 ft Clear blue sky ! 10-m (!!!) segmented primary mirror

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Constraints from QSO absorption lines: One dimensional spectrum Two dimensional spectrum Echellogram Fine absorption lines from intervening gas

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Constraints from QSO absorption lines:  A Keck/HIRES doublet Quasar Q H emission H absorption Metal absorption Over data points! C IV doublet C IV 1548Å C IV 1550Å

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future The alkali doublet (AD) method  The wavelength spacing between components of the same doublet of transitions in an alkali-like ion (e.g. C IV, Si IV and Mg II ) is roughly proportional to  for small  / .  1976: Wolfe, Brown & Roberts first applied the AD method to intervening Mg II absorption lines.  2000: Varshalovich et al. recently obtained  /  =(- 4.6 ± 4.3 ± 1.4)×10 -5 using the AD method with 16 Si IV absorption systems (average redshift=z avg =2.6).  2001: We have used improved lab wavelengths and new data from Keck to find  /  =(-0.5 ±1.3)×10 -5 (z avg =2.8).

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future The alkali doublet (AD) method  The AD method is simple … but inefficient.  The common S ground state in ADs has maximal relativistic corrections!

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future The many multiplet (MM) method  Compare light (Z~10) and heavy (Z~50) ions OR  S  P and D  P transitions in heavy ions.  More formally, we write the transition frequency as  z =  0 +q 1 x for x=(  z /  0 ) 2 –1.  We must calculate q 1 and measure  0.  Relativistic corrections for many-electron atoms:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Advantages of the MM method:  ALL relativistic corrections (i.e. even the ground state)  order of magnitude gain in precision.  All transitions appearing in a QSO absorption system may be used  statistical gain.  Many transitions  reliable determination of the velocity structure.  Positive and negative q 1  reduce systematic effects.

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Low-redshift data (Mg II /Fe II systems):

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future High-redshift data (damped Ly  systems):

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Results:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Potential systematic effects: Laboratory wavelength errors Wavelength miscalibration Heliocentric velocity variation Temperature/Pressure changes during observations Line blending Differential isotopic saturation Hyperfine structure effects Instrumental profile variations … and of course, Magnetic fields  Atmospheric refraction effects  Isotopic ratio evolution

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Wavelength calibration:  Spectra calibrated with ThAr exposures ThAr lines Quasar spectrum  Treat ThAr lines like QSO absorption lines: QSO line:  z =  0 QSO +q 1 x  ThAr line:  z =  0 ThAr +q 1 x

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future ThAr calibration results:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Atmospheric refraction effects:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Atmospheric refraction corrected results:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Isotopic ratio evolution:  Isotopic ratios are predicted and measured to vary strongly with metallicity.  For Mg and Si, the weaker isotopes get weaker with decreasing [Fe/H].  Our absorption systems have 0.01< [Fe/H] < 1.0.  Test: remove Mg and Si isotopes from our analysis.

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Zero isotopic ratio results:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Other consistency checks:  Line removal: remove each transition and fit for  /  again. Compare the  /  ’s before and after line removal. We have done this for all species and see no inconsistencies. Tests for: Lab wavelength errors, isotopic ratio and hyperfine structure variation.  “Positive-negative-shifter test”: Find the subset of systems that contain an anchor line, a positive shifter AND a negative shifter. Remove each type of line collectively and recalculate  / .  Results: subset contains 12 systems (only at high-z) No lines removed:  /  = (-1.31  0.39)  Anchors removed:  /  = (-1.49  0.44)  ve-shifters removed:  /  = (-1.54  1.03)  ve-shifters removed:  /  = (-1.41  0.65)  10 -5

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Radio constraints:  Hydrogen hyperfine transition at H = 21cm.  Molecular rotational transitions CO, HCO +, HCN, HNC, CN, CS …   H /  M   2 g P where g P is the proton magnetic g- factor.

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Radio constraints:  For y =  2 g P,  y/y =  z/(1+z) for two lines; An H I 21cm line and a molecular rotational line.  Potential for much stronger contraint on .  y/y = 10 -5

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Results to date:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future New (very preliminary) results:

Michael Murphy, UNSW University of Canterbury, New Zealand, 17/08/01 Variation in the fine structure constant?: Recent results and the future Conclusions:  There IS an effect in the data … but is it a varying  or just undiscovered systematic effects?  3 independent optical samples now agree!  Must get spectra from different telescope  UVES!  Must also find more H I 21cm/mm absorbers.  Potential constraints also from combining optical spectra and H I 21cm spectra (~ 5 good candidates).  Higher-z tests: CMB and BBN constraints.