5,883 research outputs found
The dynamics of the gravitational two-body problem at fourth post-Newtonian order and at quadratic order in the Newton constant
We derive the conservative part of the Lagrangian and the energy of a
gravitationally bound two-body system at fourth post-Newtonian order, up to
terms quadratic in the Newton constant. We also show that such terms are
compatible with Lorentz invariance and we write an ansatz for the
center-of-mass position. The remaining terms carrying higher powers of the
Newton constant are currently under investigation.Comment: 24 pages, 2 figures. Typos in formulae corrected, references added,
more comments in the conclusion in v
A 10- YSO with a Keplerian disk and a nonthermal radio jet
We previously observed the star-forming region G16.590.05 through
interferometric observations of both thermal and maser lines, and identified a
high-mass young stellar object (YSO) which is surrounded by an accretion disk
and drives a nonthermal radio jet. We performed high-angular-resolution (beam
FWHM ~0.15") 1.2-mm continuum and line observations towards G16.590.05 with
the Atacama Large Millimeter Array (ALMA). The main dust clump, with size
~10 au, is resolved into four relatively compact (diameter ~2000 au)
millimeter (mm) sources. The source harboring the high-mass YSO is the most
prominent in molecular emission. By fitting the emission profiles of several
unblended and optically thin transitions of CHOCH and CHOH, we
derived gas temperatures inside the mm-sources in the range 42--131 K, and
calculated masses of 1--5 . A well-defined Local Standard of Rest
velocity (Vlsr) gradient is detected in most of the high-density molecular
tracers at the position of the high-mass YSO, pinpointed by compact 22-GHz
free-free emission. This gradient is oriented along a direction forming a large
(~70 degree) angle with the radio jet, traced by elongated 13-GHz continuum
emission. The butterfly-like shapes of the P-V plots and the linear pattern of
the emission peaks of the molecular lines at high velocity confirm that this
Vlsr gradient is due to rotation of the gas in the disk surrounding the
high-mass YSO. The disk radius is ~500 au, and the Vlsr distribution along the
major axis of the disk is well reproduced by a Keplerian profile around a
central mass of 102 . The position of the YSO is offset by >~
0.1" from the axis of the radio jet and the dust emission peak. To explain this
displacement we argue that the high-mass YSO could have moved from the center
of the parental mm source owing to dynamical interaction with one or more
companions.Comment: 16 pages, 12 figures, accepted by Astronomy & Astrophysics, Main
Journa
Models of Scherk-Schwarz Symmetry Breaking in 5D: Classification and Calculability
The form of the most general orbifold breaking of gauge, global and supersymmetries with a single extra dimension is given. In certain theories the Higgs boson mass is ultraviolet finite due to an unbroken local supersymmetry, which is explicitly exhibited. We construct: a 1 parameter SU(3) \times SU(2) \times U(1) theory with 1 bulk Higgs hypermultiplet, a 2 parameter SU(3) \times SU(2) \times U(1) theory with 2 bulk Higgs hypermultiplets, and a 2 parameter SU(5) \to SU(3) \times SU(2) \times U(1) theory with 2 bulk Higgs hypermultiplets, and demonstrate that these theories are unique. We compute the Higgs mass and compactification scale in the SU(3) \times SU(2) \times U(1) theory with 1 bulk Higgs hypermultiplet
Surface phase transitions in one-dimensional channels arranged in a triangular cross-sectional structure: Theory and Monte Carlo simulations
Monte Carlo simulations and finite-size scaling analysis have been carried
out to study the critical behavior in a submonolayer lattice-gas of interacting
monomers adsorbed on one-dimensional channels arranged in a triangular
cross-sectional structure. The model mimics a nanoporous environment, where
each nanotube or unit cell is represented by a one-dimensional array. Two kinds
of lateral interaction energies have been considered: , interaction
energy between nearest-neighbor particles adsorbed along a single channel and
, interaction energy between particles adsorbed across
nearest-neighbor channels. For and , successive planes are
uncorrelated, the system is equivalent to the triangular lattice and the
well-known
ordered phase is found at low temperatures and a coverage, , of 1/3
. In the more general case ( and ), a
competition between interactions along a single channel and a transverse
coupling between sites in neighboring channels allows to evolve to a
three-dimensional adsorbed layer. Consequently, the and structures "propagate" along the
channels and new ordered phases appear in the adlayer. The Monte Carlo
technique was combined with the recently reported Free Energy Minimization
Criterion Approach (FEMCA), to predict the critical temperatures of the
order-disorder transformation. The excellent qualitative agreement between
simulated data and FEMCA results allow us to interpret the physical meaning of
the mechanisms underlying the observed transitions.Comment: 24 pages, 6 figure
Quantum systems in a stationary environment out of thermal equilibrium
We discuss how the thermalization of an elementary quantum system is modified
when the system is placed in an environment out of thermal equilibrium. To this
aim we provide a detailed investigation of the dynamics of an atomic system
placed close to a body of arbitrary geometry and dielectric permittivity, whose
temperature is different from that of the surrounding walls . A
suitable master equation for the general case of an -level atom is first
derived and then specialized to the cases of a two- and three-level atom.
Transition rates and steady states are explicitly expressed as a function of
the scattering matrices of the body and become both qualitatively and
quantitatively different from the case of radiation at thermal equilibrium. Out
of equilibrium, the system steady state depends on the system-body distance, on
the geometry of the body and on the interplay of all such parameters with the
body optical resonances. While a two-level atom tends toward a thermal state,
this is not the case already in the presence of three atomic levels. This
peculiar behavior can be exploited, for example, to invert the populations
ordering and to provide an efficient cooling mechanism for the internal state
of the quantum system. We finally provide numerical studies and asymptotic
expressions when the body is a slab of finite thickness. Our predictions can be
relevant for a wide class of experimental configurations out of thermal
equilibrium involving different physical realizations of two or three-level
systems.Comment: 20 pages, 15 figures, published versio
Simulation of underground gravity gradients from stochastic seismic fields
We present results obtained from a finite-element simulation of seismic
displacement fields and of gravity gradients generated by those fields. The
displacement field is constructed by a plane wave model with a 3D isotropic
stochastic field and a 2D fundamental Rayleigh field. The plane wave model
provides an accurate representation of stationary fields from distant sources.
Underground gravity gradients are calculated as acceleration of a free test
mass inside a cavity. The results are discussed in the context of
gravity-gradient noise subtraction in third generation gravitational-wave
detectors. Error analysis with respect to the density of the simulated grid
leads to a derivation of an improved seismometer placement inside a 3D array
which would be used in practice to monitor the seismic field.Comment: 24 pages, 12 figure
Hidden in plain sight: a massive, dusty starburst in a galaxy protocluster at z=5.7 in the COSMOS field
We report the serendipitous discovery of a dusty, starbursting galaxy at
(hereafter called CRLE) in close physical association with the
"normal" main-sequence galaxy HZ10 at . CRLE was identified by
detection of [CII], [NII] and CO(2-1) line emission, making it the highest
redshift, most luminous starburst in the COSMOS field. This massive, dusty
galaxy appears to be forming stars at a rate of at least 1500
yr in a compact region only kpc in diameter. The dynamical and
dust emission properties of CRLE suggest an ongoing merger driving the
starburst, in a potentially intermediate stage relative to other known dusty
galaxies at the same epoch. The ratio of [CII] to [NII] may suggest that an
important () contribution to the [CII] emission comes from a diffuse
ionized gas component, which could be more extended than the dense,
starbursting gas. CRLE appears to be located in a significant galaxy
overdensity at the same redshift, potentially associated with a large-scale
cosmic structure recently identified in a Lyman Alpha Emitter survey. This
overdensity suggests that CRLE and HZ10 reside in a protocluster environment,
offering the tantalizing opportunity to study the effect of a massive starburst
on protocluster star formation. Our findings support the interpretation that a
significant fraction of the earliest galaxy formation may occur from the inside
out, within the central regions of the most massive halos, while rapidly
evolving into the massive galaxy clusters observed in the local Universe.Comment: 16 pages, 9 figures, 4 tables, final version to appear on ApJ
(accepted May 19, 2018
Resonant nonlinear quantum transport for a periodically kicked Bose condensate
Our realistic numerical results show that the fundamental and higher-order
quantum resonances of the delta-kicked rotor are observable in state-of-the-art
experiments with a Bose condensate in a shallow harmonic trap, kicked by a
spatially periodic optical lattice. For stronger confinement,
interaction-induced destruction of the resonant motion of the kicked harmonic
oscillator is predicted.Comment: amended version, new Fig.
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