6,381 research outputs found
Go with the Flow, Average Holographic Universe
Gravity is a macroscopic manifestation of a microscopic quantum theory of
space-time, just as the theories of elasticity and hydrodynamics are the
macroscopic manifestation of the underlying quantum theory of atoms. The
connection of gravitation and thermodynamics is long and deep. The observation
that space-time has a temperature for accelerating observers and horizons is
direct evidence that there are underlying microscopic degrees of freedom. The
equipartition of energy, meaning of temperature, in these modes leads one to
anticipate that there is also an entropy associated. When this entropy is
maximized on a volume of space-time, then one retrieves the metric of
space-time (i.e. the equations of gravity, e.g. GR). Since the metric satisfies
the extremum in entropy on the volume, then the volume integral of the entropy
can readily be converted to surface integral, via Gauss's Theorem. This surface
integral is simply an integral of the macroscopic entropy flow producing the
mean entropy holographic principle. This approach also has the added value that
it naturally dispenses with the cosmological constant/vacuum energy problem in
gravity except perhaps for second order quantum effects on the mean surface
entropy.Comment: 14 page
Offset balancing in pseudo-correlation radiometers for CMB measurements
Radiometeric CMB measurements need to be highly stable and this stability is
best obtained with differential receivers. The residual 1/f noise in the
differential output is strongly dependent on the radiometer input offset which
can be cancelled using various balancing strategies. In this paper we discuss a
software method implemented in the Planck-LFI pseudo-correlation receivers
which uses a tunable "gain modulation factor, r, in the sky-load difference.
Numerical simulations and experimental data show how proper tuning of the
parameter r ensures a very stable differential output with knee frequencies of
the order of few mHz. Various approaches to calculate r using the radiometer
total power data are discussed with some examples relevant to Planck-LFI.
Although the paper focuses on pseudo-correlation receivers and the examples are
relative to Planck-LFI, the proposed method and its analysis is general and can
be applied to a large class of differential radiometric receivers.Comment: 12 pages, 8 figures, accepted for publication in A&A (updated version
with few editorial changes
Aether Drift and the isotropy of the universe: A measurement of anisotropes in the primordial black-body radiation
Large-angular-scale anisotropies in the 3 K primordial black-body radiation were detected and mapped with a sensitivity of 2 x to the minus 4 power K and an angular resolution of about 10 deg. The motion of the Earth with respect to the distant matter of the Universe ("Aether Drift") was measured and the homogeneity and isotropy of the Universe (the "Cosmological Principle") was probed. The experiment uses two Dicke radiometers, one at 33 GHz to detect the cosmic anisotropy, and one at 54 GHz to detect anisotropies in the residual oxygen above the detectors. The system was installed in the NASA-Ames Earth survey aircraft (U-2), and operated successfully in a series of flights in both the Northern and Southern Hemispheres. Data taking and analysis to measure the anisotropy were successful
- …
