89 research outputs found
A constraint on a varying proton--electron mass ratio 1.5 billion years after the Big Bang
A molecular hydrogen absorber at a lookback time of 12.4 billion years,
corresponding to 10 of the age of the universe today, is analyzed to put a
constraint on a varying proton--electron mass ratio, . A high resolution
spectrum of the J14432724 quasar, which was observed with the Very Large
Telescope, is used to create an accurate model of 89 Lyman and Werner band
transitions whose relative frequencies are sensitive to , yielding a limit
on the relative deviation from the current laboratory value of
.Comment: Accepted for publication in PRL. Includes supplemental materia
The CO A-X System for Constraining Cosmological Drift of the Proton-Electron Mass Ratio
The band system of carbon monoxide,
which has been detected in six highly redshifted galaxies (), is
identified as a novel probe method to search for possible variations of the
proton-electron mass ratio () on cosmological time scales. Laboratory
wavelengths of the spectral lines of the A-X (,0) bands for have
been determined at an accuracy of
through VUV Fourier-transform absorption spectroscopy, providing a
comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0)
bands, two-photon Doppler-free laser spectroscopy has been applied at the accuracy level, verifying the absorption data. Sensitivity
coefficients for a varying have been calculated for the CO A-X
bands, so that an operational method results to search for -variation.Comment: 7 pages (main article), 3 figures, includes supplementary materia
Search for varying constants of nature from astronomical observation of molecules
The status of searches for possible variation in the constants of nature from
astronomical observation of molecules is reviewed, focusing on the
dimensionless constant representing the proton-electron mass ratio
. The optical detection of H and CO molecules with large
ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as
the detection of H with the Cosmic Origins Spectrograph aboard the Hubble
Space Telescope is discussed in the context of varying constants, and in
connection to different theoretical scenarios. Radio astronomy provides an
alternative search strategy bearing the advantage that molecules as NH
(ammonia) and CHOH (methanol) can be used, which are much more sensitive to
a varying than diatomic molecules. Current constraints are
for redshift , corresponding to
look-back times of 10-12.5 Gyrs, and for
, corresponding to half the age of the Universe (both at 3
statistical significance). Existing bottlenecks and prospects for future
improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the
International Space Science Institute, Bern 201
Limits on a gravitational field dependence of the proton-electron mass ratio from H2 in white dwarf stars.
Spectra of molecular hydrogen (H2) are employed to search for a possible proton-to-electron mass ratio (ÎŒ) dependence on gravity. The Lyman transitions of H2, observed with the Hubble Space Telescope towards white dwarf stars that underwent a gravitational collapse, are compared to accurate laboratory spectra taking into account the high temperature conditions (TâŒ13â000ââK) of their photospheres. We derive sensitivity coefficients Ki which define how the individual H2 transitions shift due to ÎŒ dependence. The spectrum of white dwarf star GD133 yields a ÎÎŒ/ÎŒ constraint of (-2.7±4.7stat±0.2syst)Ă10(-5) for a local environment of a gravitational potential ÏâŒ10(4) ÏEarth, while that of G29-38 yields ÎÎŒ/ÎŒ=(-5.8±3.8stat±0.3syst)Ă10(-5) for a potential of 2Ă10(4) ÏEarth.This work was supported by the FOM-Program \Bro-
ken Mirrors & Drifting Constant", Science and Technol-
ogy Facilities Council, Templeton Foundation and Aus-
tralian Research Council (DP110100866).This is the accepted manuscript. The final version is available from APS at http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.123002
The inhomogeneous ISM toward PKS1830-211 SW - A detailed view on molecular gas at a look-back time of 7.5 Gyr
Based on measurements with the Effelsberg 100-m telescope, a multi-line study
of molecular species is presented toward the south-western source of the
gravitational lens system PKS 1830-211, which is by far the best known target
to study molecular gas in absorption at intermediate redshift. Determining line
parameters and optical depths and performing Large Velocity Gradient radiative
transfer calculations, the aims of this study are (1) to evaluate physical
parameters of the absorbing foreground gas at z~0.89, in particular its
homogeneity, and (2) to monitor the spectroscopic time variability caused by
fluctuations of the z~2.5 background continuum source. We find, that the gas is
quite inhomogeneous with n(H2)~2 x 10^3 cm^-3 for most molecular species but
with higher values for H2CO and lower ones for SO. Measuring the CS J=1-0
transition during a time interval of more than a decade, from 2001 to 2012, the
peak absorption depth of the line remains approximately constant, while the
line shape undergoes notable variations. Covering the time between 1996 and
2013, CS, HCO+, and CH3OH data indicate maximal integrated optical depths in
~2001 and 2011/2012. This is compatible with a ~10 yr periodicity, which,
however, needs confirmation by substantially longer time monitoring. Comparing
molecular abundances with those of different types of Galactic and nearby
extragalactic clouds we find that the observed cloud complex does not
correspond to one particular type but to a variety of cloud types with more
diffuse and denser components as can be expected for an observed region with a
transverse linear scale of several parsec and a likely larger depth along the
line-of-sight. A tentative detection of Galactic absorption in the c-C3H2
1(10)-1(01) line at 18.343 GHz is also reported.Comment: Accepted for publication in A&A, 11 pages, 10 figures, 4 table
The inhomogeneous ISM toward PKS 1830â211 SW: A detailed view of molecular gas at a look-back time of 7.5 Gyr
Based on measurements with the Effelsberg 100-m telescope, a multiline study of molecular species is presented toward the southwestern source of the gravitational lens system PKSâ1830â211, which is by far the best known target for studying molecular gas in absorption at intermediate redshift. Determining line parameters and optical depths and performing large velocity gradient radiative transfer calculations, the aims of this study are (1) to evaluate physical parameters of the absorbing foreground gas at z ~ 0.89, in particular its homogeneity; and (2) to monitor the spectroscopic time variability caused by fluctuations in the z ~ 2.5 background continuum source. We find, that the gas is quite inhomogeneous with n(H2) ~ 2 Ă 103 cm-3 for most molecular species but with higher values for H2CO and lower ones for SO. Measuring the CS J = 1 â 0 transition during a time interval of more than a decade, from 2001 to 2012, the peak absorption depth of the line remains approximately constant, while the line shape undergoes notable variations. Covering the time between 1996 and 2013, CS, HCO+, and CH3OH data indicate maximum integrated optical depths in ~2001 and 2011/2012. This is compatible with a ~10 yr periodicity, which, however, needs confirmation by substantially longer time monitoring. Comparing molecular abundances with those of different types of Galactic and nearby extragalactic clouds we find that the observed cloud complex does not correspond to one particular type but to a variety of cloud types with more diffuse and denser components as can be expected for an observed region with a transverse linear scale of several parsec and a likely greater depth along the line of sight. A tentative detection of Galactic absorption in the c-C3H2 110â101 line at 18.343 GHz is also reported
Cosmological evolution of the Higgs boson's vacuum expectation value
We point out that the expansion of the universe leads to a cosmological time evolution of the vacuum expectation of the Higgs boson. Within the standard model of particle physics, the cosmological time evolution of the vacuum expectation of the Higgs leads to a cosmological time evolution of the masses of the fermions and of the electroweak gauge bosons while the scale of Quantum Chromodynamics (QCD) remains constant. Precise measurements of the cosmological time evolution of u=me/mp, where me and mp are respectively the electron and proton mass (which is essentially determined by the QCD scale), therefore provide a test of the standard models of particle physics and of cosmology. This ratio can be measured using modern atomic clocks
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