5,780 research outputs found
Binary Pulsar Constraints on the Parameterized post-Einsteinian Framework
We constrain the parameterized post-Einsteinian framework with binary pulsar
observations of orbital period decay due to gravitational wave emission. This
framework proposes to enhance the amplitude and phase of gravitational waveform
templates through post-Einsteinian parameters to search for generic deviations
from General Relativity in gravitational wave data. Such enhancements
interpolate between General Relativity and alternative theory predictions, but
their magnitude must be such as to satisfy all current experiments and
observations. The data that currently constrains the parameterized
post-Einsteinian framework the most is the orbital period decay of binary
pulsars. We use such observations to place upper limits on the magnitude of
post-Einsteinian parameters, which will be critical when gravitational waves
are detected and this framework is implemented.Comment: 4 pages, 2 figures, submitted to Phys. Rev.
Sound clocks and sonic relativity
Sound propagation within certain non-relativistic condensed matter models
obeys a relativistic wave equation despite such systems admitting entirely
non-relativistic descriptions. A natural question that arises upon
consideration of this is, "do devices exist that will experience the relativity
in these systems?" We describe a thought experiment in which 'acoustic
observers' possess devices called sound clocks that can be connected to form
chains. Careful investigation shows that appropriately constructed chains of
stationary and moving sound clocks are perceived by observers on the other
chain as undergoing the relativistic phenomena of length contraction and time
dilation by the Lorentz factor, with c the speed of sound. Sound clocks within
moving chains actually tick less frequently than stationary ones and must be
separated by a shorter distance than when stationary to satisfy simultaneity
conditions. Stationary sound clocks appear to be length contracted and time
dilated to moving observers due to their misunderstanding of their own state of
motion with respect to the laboratory. Observers restricted to using sound
clocks describe a universe kinematically consistent with the theory of special
relativity, despite the preferred frame of their universe in the laboratory.
Such devices show promise in further probing analogue relativity models, for
example in investigating phenomena that require careful consideration of the
proper time elapsed for observers.Comment: (v2) consistent with published version; (v1) 15 pages, 9 figure
Many body localization and thermalization: insights from the entanglement spectrum
We study the entanglement spectrum in the many body localizing and
thermalizing phases of one and two dimensional Hamiltonian systems, and
periodically driven `Floquet' systems. We focus on the level statistics of the
entanglement spectrum as obtained through numerical diagonalization, finding
structure beyond that revealed by more limited measures such as entanglement
entropy. In the thermalizing phase the entanglement spectrum obeys level
statistics governed by an appropriate random matrix ensemble. For Hamiltonian
systems this can be viewed as evidence in favor of a strong version of the
eigenstate thermalization hypothesis (ETH). Similar results are also obtained
for Floquet systems, where they constitute a result `beyond ETH', and show that
the corrections to ETH governing the Floquet entanglement spectrum have
statistical properties governed by a random matrix ensemble. The particular
random matrix ensemble governing the Floquet entanglement spectrum depends on
the symmetries of the Floquet drive, and therefore can depend on the choice of
origin of time. In the many body localized phase the entanglement spectrum is
also found to show level repulsion, following a semi-Poisson distribution (in
contrast to the energy spectrum, which follows a Poisson distribution). This
semi-Poisson distribution is found to come mainly from states at high
entanglement energies. The observed level repulsion only occurs for interacting
localized phases. We also demonstrate that equivalent results can be obtained
by calculating with a single typical eigenstate, or by averaging over a
microcanonical energy window - a surprising result in the localized phase. This
discovery of new structure in the pattern of entanglement of localized and
thermalizing phases may open up new lines of attack on many body localization,
thermalization, and the localization transition.Comment: 17 pages, 20 figure
Characterizing the many-body localization transition through the entanglement spectrum
We numerically explore the many body localization (MBL) transition through
the lens of the {\it entanglement spectrum}. While a direct transition from
localization to thermalization is believed to obtain in the thermodynamic limit
(the exact details of which remain an open problem), in finite system sizes
there exists an intermediate `quantum critical' regime. Previous numerical
investigations have explored the crossover from thermalization to criticality,
and have used this to place a numerical {\it lower} bound on the critical
disorder strength for MBL. A careful analysis of the {\it high energy} part of
the entanglement spectrum (which contains universal information about the
critical point) allows us to make the first ever observation in exact numerics
of the crossover from criticality to MBL and hence to place a numerical {\it
upper bound} on the critical disorder strength for MBL.Comment: 4 pages+appendi
Constraints on Electroweak Effective Operators at One Loop
We derive bounds on nine dimension-six operators involving electroweak gauge
bosons and the Higgs boson from precision electroweak data. Four of these
operators contribute at tree level, and five contribute only at one loop. Using
the full power of effective field theory, we show that the bounds on the five
loop-level operators are much weaker than previously claimed, and thus much
weaker than bounds from tree-level processes at high-energy colliders.Comment: 15 page
The elemental composition of the Sun II. The iron group elements Sc to Ni
We redetermine the abundances of all iron group nuclei in the Sun, based on
neutral and singly-ionised lines of Sc, Ti, V, Mn, Fe, Co and Ni in the solar
spectrum. We employ a realistic 3D hydrodynamic model solar atmosphere,
corrections for departures from local thermodynamic equilibrium (NLTE),
stringent line selection procedures and high quality observational data. We
have scoured the literature for the best quality oscillator strengths,
hyperfine constants and isotopic separations available for our chosen lines. We
find , , ,
, , ,
and . Our uncertainties factor in both statistical
and systematic errors (the latter estimated for possible errors in the model
atmospheres and NLTE line formation). The new abundances are generally in good
agreement with the CI meteoritic abundances but with some notable exceptions.
This analysis constitutes both a full exposition and a slight update of the
preliminary results we presented in Asplund, Grevesse, Sauval & Scott
(arXiv:0909.0948), including full line lists and details of all input data we
employed.Comment: 10 figures, 24 pages + 10 online-only pages of tables. v2. Matches
version accepted by A&
The elemental composition of the Sun III. The heavy elements Cu to Th
We re-evaluate the abundances of the elements in the Sun from copper ()
to thorium (). Our results are mostly based on neutral and singly-ionised
lines in the solar spectrum. We use the latest 3D hydrodynamic solar model
atmosphere, and in a few cases also correct for departures from local
thermodynamic equilibrium (LTE) using non-LTE (NLTE) calculations performed in
1D. In order to minimise statistical and systematic uncertainties, we make
stringent line selections, employ the highest-quality observational data and
carefully assess oscillator strengths, hyperfine constants and isotopic
separations available in the literature, for every line included in our
analysis. Our results are typically in good agreement with the abundances in
the most pristine meteorites, but there are some interesting exceptions. This
analysis constitutes both a full exposition and a slight update of the relevant
parts of the preliminary results we presented in Asplund, Grevesse, Sauval &
Scott (arXiv:0909.0948), including full line lists and details of all input
data that we have employed.Comment: 5 figures, 18 pages + 6 online-only pages of tables. v2. Matches
version accepted by A&
- …