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Title: 21-cm Radiation: A New Probe of Variation in the Fine-Structure Constant

Abstract

We investigate the effect of variation in the value of the fine-structure constant ({alpha}) at high redshifts (recombination >z>30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in {alpha} and it is so far the only probe of the fine-structure constant in this redshift range. A change in the value of {alpha} by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by >5% over the redshift range z<50. There is an effect of similar magnitude on the amplitude of the fluctuations in the brightness temperature. The redshift of maximum absorption also changes by {approx}5%.

Authors:
;  [1];  [2]
  1. Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20957743
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevLett.98.111301; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; BRIGHTNESS; FINE STRUCTURE; HYDROGEN; RECOMBINATION; RELICT RADIATION; SIGNALS

Citation Formats

Khatri, Rishi, Wandelt, Benjamin D., and Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801. 21-cm Radiation: A New Probe of Variation in the Fine-Structure Constant. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.111301.
Khatri, Rishi, Wandelt, Benjamin D., & Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801. 21-cm Radiation: A New Probe of Variation in the Fine-Structure Constant. United States. doi:10.1103/PHYSREVLETT.98.111301.
Khatri, Rishi, Wandelt, Benjamin D., and Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801. Fri . "21-cm Radiation: A New Probe of Variation in the Fine-Structure Constant". United States. doi:10.1103/PHYSREVLETT.98.111301.
@article{osti_20957743,
title = {21-cm Radiation: A New Probe of Variation in the Fine-Structure Constant},
author = {Khatri, Rishi and Wandelt, Benjamin D. and Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801},
abstractNote = {We investigate the effect of variation in the value of the fine-structure constant ({alpha}) at high redshifts (recombination >z>30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in {alpha} and it is so far the only probe of the fine-structure constant in this redshift range. A change in the value of {alpha} by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by >5% over the redshift range z<50. There is an effect of similar magnitude on the amplitude of the fluctuations in the brightness temperature. The redshift of maximum absorption also changes by {approx}5%.},
doi = {10.1103/PHYSREVLETT.98.111301},
journal = {Physical Review Letters},
number = 11,
volume = 98,
place = {United States},
year = {Fri Mar 16 00:00:00 EDT 2007},
month = {Fri Mar 16 00:00:00 EDT 2007}
}
  • A Comment on the Letter by Rishi Khatri and Benjamin D. Wandelt, Phys. Rev. Lett. 98, 111301 (2007). The authors of the Letter offer a Reply.
  • We show that using the modified form of the Dirac Hamiltonian as suggested by Bekenstein does not affect the analysis of QSO data pertaining to a measurement of {alpha} variation. We obtain the present time limit on Bekenstein's parameter, tan{sup 2} {chi}=(0.2{+-}0.7)x10{sup -6}, from the measurement of the hydrogen 2p fine structure using a value of {alpha} obtained from different experiments.
  • A comparison of different atomic frequency standards over time can be used to perform a measurement of 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. We have measured an optical transition frequency at 688 THz in Yb+ with a cesium atomic clock at two times separated by 2.8 years and find that a variation of this frequency can be excluded within a 1{sigma} relative uncertainty of 4.4{center_dot}10-15 yr-1. Combined with recently published values for the constancy of other transition frequencies this measurementmore » provides a limit on the present variability of {alpha} at the level of 2.0{center_dot}10-15 yr-1. Constraints are also derived for the drift rates of other fundamental constants like the electron/proton mass ratio and the proton g-factor.« less
  • The configuration interaction in many-electron atoms may cause anomalies in the fine structure which make the intervals small and very sensitive to variation of the fine-structure constant. Repeated precision measurements of these intervals over a long period of time can put strong constraints on possible time variation of the fine-structure constant. We consider the 5p{sup 4} {sup 3}P{sub 2,1,0} fine-structure multiplet in the ground state of neutral tellurium as an example. Here the effect of change of the fine structure constant is enhanced about 100 times in the relative change of the small energy interval between the {sup 3}P{sub 1}more » and {sup 3}P{sub 0} states.« less
  • No abstract prepared.