30,216 research outputs found
Detecting primordial gravitational waves with circular polarization of the redshifted 21 cm line: II. Forecasts
In the first paper of this series, we showed that the CMB quadrupole at high
redshifts results in a small circular polarization of the emitted 21 cm
radiation. In this paper we forecast the sensitivity of future radio
experiments to measure the CMB quadrupole during the era of first cosmic light
(). The tomographic measurement of 21 cm circular polarization allows
us to construct a 3D remote quadrupole field. Measuring the -mode component
of this remote quadrupole field can be used to put bounds on the
tensor-to-scalar ratio . We make Fisher forecasts for a future Fast Fourier
Transform Telescope (FFTT), consisting of an array of dipole antennas in a
compact grid configuration, as a function of array size and observation time.
We find that a FFTT with a side length of 100 km can achieve after ten years of observation and with a sky coverage
. The forecasts are dependent on the evolution of the
Lyman- flux in the pre-reionization era, that remains observationally
unconstrained. Finally, we calculate the typical order of magnitudes for
circular polarization foregrounds and comment on their mitigation strategies.
We conclude that detection of primordial gravitational waves with 21 cm
observations is in principle possible, so long as the primordial magnetic field
amplitude is small, but would require a very futuristic experiment with
corresponding advances in calibration and foreground suppression techniques.Comment: 19 pages, matches PRD accepted versio
Spin-Charge Decoupling and Orthofermi Quantum Statistics
Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.Comment: 12 pages, LaTex Journal_ref: A slightly abridged version of this
paper has appeared as a brief report in Phys. Rev. B, Vol. 63, 132405 (2001
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