6,460 research outputs found
Methanol as a tracer of fundamental constants
The methanol molecule CH3OH has a complex microwave spectrum with a large
number of very strong lines. This spectrum includes purely rotational
transitions as well as transitions with contributions of the internal degree of
freedom associated with the hindered rotation of the OH group. The latter takes
place due to the tunneling of hydrogen through the potential barriers between
three equivalent potential minima. Such transitions are highly sensitive to
changes in the electron-to-proton mass ratio, mu = m_e/m_p, and have different
responses to mu-variations. The highest sensitivity is found for the mixed
rotation-tunneling transitions at low frequencies. Observing methanol lines
provides more stringent limits on the hypothetical variation of mu than ammonia
observation with the same velocity resolution. We show that the best quality
radio astronomical data on methanol maser lines constrain the variability of mu
in the Milky Way at the level of |Delta mu/mu| < 28x10^{-9} (1sigma) which is
in line with the previously obtained ammonia result, |Delta mu/mu| < 29x10^{-9}
(1\sigma). This estimate can be further improved if the rest frequencies of the
CH3OH microwave lines will be measured more accurately.Comment: 7 pages, 1 table, 1 figure. Accepted for publication in Ap
Trapped modes in zigzag graphene nanoribbons
We study a scattering on an ultra-low potential in zigzag graphene
nanoribbon. Using mathematical framework based on the continuous Dirac model
and augumented scattering matrix, we derive a condition for the existence of a
trapped mode. We consider the threshold energies where the continuous spectrum
changes its multiplicity and show that the trapped modes may appear for
energies slightly less than a threshold and its multiplicity does not exceeds
one. We prove that trapped modes do not appear outside the threshold, provided
the potential is sufficiently small
Sensitivity of the H3O+ inversion-rotational spectrum to changes in m_e/m_p
Quantum mechanical tunneling inversion transition in ammonia NH3 is actively
used as a sensitive tool to study possible variations of the electron-to-proton
mass ratio, mu = m_e/m_p. The molecule H3O+ has the inversion barrier
significantly lower than that of NH3. Consequently, its tunneling transition
occurs in the far-infrared (FIR) region and mixes with rotational transitions.
Several such FIR and submillimiter transitions are observed from the
interstellar medium in the Milky Way and in nearby galaxies. We show that the
rest-frame frequencies of these transitions are very sensitive to the variation
of mu, and that their sensitivity coefficients have different signs. Thus, H3O+
can be used as an independent target to test hypothetical changes in mu
measured at different ambient conditions of high (terrestrial) and low
(interstellar medium) matter densities. The environmental dependence of mu and
coupling constants is suggested in a class of chameleon-type scalar field
models - candidates to dark energy carrier.Comment: 8 pages, 2 figures, accepted to ApJ; v2: reformatted for ApJ and
discussion of systematics significantly extende
Electric dipole moment enhancement factor of thallium
The goal of this work is to resolve the present controversy in the value of
the EDM enhancement factor of Tl. We have carried out several calculations by
different high-precision methods, studied previously omitted corrections, as
well as tested our methodology on other parity conserving quantities. We find
the EDM enhancement factor of Tl to be equal to -573(20). This value is 20%
larger than the recently published result of Nataraj et al. [Phys. Rev. Lett.
106, 200403 (2011)], but agrees very well with several earlier results.Comment: 5 pages; v2: link to supplemental material adde
Electric dipole moment of the electron in YbF molecule
Ab initio calculation of the hyperfine, P-odd, and P,T-odd constants for the
YbF molecule was performed with the help of the recently developed technique,
which allows to take into account correlations and polarization in the
outercore region. The ground state electronic wave function of the YbF molecule
is found with the help of the Relativistic Effective Core Potential method
followed by the restoration of molecular four-component spinors in the core
region of ytterbium in the framework of a non-variational procedure. Core
polarization effects are included with the help of the atomic Many Body
Perturbation Theory for Yb atom. For the isotropic hyperfine constant A,
accuracy of our calculation is about 3% as compared to the experimental datum.
The dipole constant Ad (which is much smaller in magnitude), though better than
in all previous calculations, is still underestimated by almost 23%. Being
corrected within a semiempirical approach for a perturbation of 4f-shell in the
core of Yb due to the bond making, this error is reduced to 8%. Our value for
the effective electric field on the unpaired electron is 4.9 a.u.=2.5E+10 V/cm.Comment: 7 pages, REVTE
Bose-Einstein correlations at LEP and Tevatron energies
Using the Bose-Einstein correlations (BEC) implemented in PYTHIA we
investigated a possibility of the CDF experiment at the Tevatron to see the
two-particle correlations in the final state of interactions. The approach
based on quantum field theory at finite temperature was applied to the ALEPH
data at LEP, and the BEC important parameters were retrieved.Comment: 5 pages, 4 figures, 1 table. Based on the talk gived at The 6th
international workshop on very high multiplicity physics, JINR Dubna, 16-17
april 2005. In Table 1. the sign of error adde
- …