3,533 research outputs found
What measurable zero point fluctuations can(not) tell us about dark energy
We show that laboratory experiments cannot measure the absolute value of dark
energy. All known experiments rely on electromagnetic interactions. They are
thus insensitive to particles and fields that interact only weakly with
ordinary matter. In addition, Josephson junction experiments only measure
differences in vacuum energy similar to Casimir force measurements. Gravity,
however, couples to the absolute value. Finally we note that Casimir force
measurements have tested zero point fluctuations up to energies of ~10 eV, well
above the dark energy scale of ~0.01 eV. Hence, the proposed cut-off in the
fluctuation spectrum is ruled out experimentally.Comment: 4 page
Zeroth Law compatibility of non-additive thermodynamics
Non-extensive thermodynamics was criticized among others by stating that the
Zeroth Law cannot be satisfied with non-additive composition rules. In this
paper we determine the general functional form of those non-additive
composition rules which are compatible with the Zeroth Law of thermodynamics.
We find that this general form is additive for the formal logarithms of the
original quantities and the familiar relations of thermodynamics apply to
these. Our result offers a possible solution to the longstanding problem about
equilibrium between extensive and non-extensive systems or systems with
different non-extensivity parameters.Comment: 18 pages, 1 figur
Commuting self-adjoint extensions of symmetric operators defined from the partial derivatives
We consider the problem of finding commuting self-adjoint extensions of the
partial derivatives {(1/i)(\partial/\partial x_j):j=1,...,d} with domain
C_c^\infty(\Omega) where the self-adjointness is defined relative to
L^2(\Omega), and \Omega is a given open subset of R^d. The measure on \Omega is
Lebesgue measure on R^d restricted to \Omega. The problem originates with I.E.
Segal and B. Fuglede, and is difficult in general. In this paper, we provide a
representation-theoretic answer in the special case when \Omega=I\times\Omega_2
and I is an open interval. We then apply the results to the case when \Omega is
a d-cube, I^d, and we describe possible subsets \Lambda of R^d such that
{e^(i2\pi\lambda \dot x) restricted to I^d:\lambda\in\Lambda} is an orthonormal
basis in L^2(I^d).Comment: LaTeX2e amsart class, 18 pages, 2 figures; PACS numbers 02.20.Km,
02.30.Nw, 02.30.Tb, 02.60.-x, 03.65.-w, 03.65.Bz, 03.65.Db, 61.12.Bt,
61.44.B
The SkyMapper search for extremely metal-poor stars in the Large Magellanic Cloud
We present results of a search for extremely metal-poor (EMP) stars in the
Large Magellanic Cloud, which can provide crucial information about the
properties of the first stars as well as on the formation conditions prevalent
during the earliest stages of star formation in dwarf galaxies. Our search
utilised SkyMapper photometry, together with parallax and proper motion cuts
(from Gaia), colour-magnitude cuts (by selecting the red giant branch region)
and finally a metallicity-sensitive cut. Low-resolution spectra of a sample of
photometric candidates were taken using the ANU 2.3m telescope/WiFeS
spectrograph, from which 7 stars with [Fe/H] -2.75 were identified, two
of which have [Fe/H] -3. Radial velocities, derived from the CaII
triplet lines, closely match the outer rotation curve of the LMC for the
majority of the candidates in our sample. Therefore, our targets are robustly
members of the LMC based on their 6D phase-space information (coordinates,
spectrophotometric distance, proper motions and radial velocities), and they
constitute the most metal-poor stars so far discovered in this galaxy.Comment: Accepted for publication in MNRA
Frequency Domain Functional Near-Infrared Spectrometer (fNIRS) for Crew State Monitoring
A frequency domain functional near-infrared spectrometer (fNIRS) and accompanying software have been developed by the NASA Glenn Research Center as part of the Airspace Operations and Safety Program (AOSP) Technologies for Airplane State Awareness (TASA)SE211 Crew State Monitoring (CSM) Project. The goal of CSM was to develop a suite of instruments to measure the cognitive state of operators while performing operational activities. The fNIRS was one of the instruments intended for the CSM, developed to measure changes in oxygen levels in the brain noninvasively
The Outer Envelopes of Globular Clusters. I. NGC 7089 (M2)
We present the results of a wide-field imaging survey of the periphery of the
Milky Way globular cluster NGC 7089 (M2). Data were obtained with MegaCam on
the Magellan Clay Telescope, and the Dark Energy Camera on the Blanco
Telescope. We find that M2 is embedded in a diffuse stellar envelope extending
to a radial distance of at least ( pc) -- five
times the nominal tidal radius of the cluster. The envelope appears nearly
circular in shape, has a radial density decline well described by a power law
of index , and contains approximately of the
luminosity of the entire system. While the origin of the envelope cannot be
robustly identified using the presently available data, the fact that M2 also
hosts stellar populations exhibiting a broad dispersion in the abundances of
both iron and a variety of neutron capture elements suggests that this object
might plausibly constitute the stripped nucleus of a dwarf Galaxy that was long
ago accreted and destroyed by the Milky Way.Comment: 15 pages, 12 figures, accepted for publishing in MNRA
Multivariate p-dic L-function
We construct multivariate p-adic L-function in the p-adic number fild by
using Washington method.Comment: 9 page
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