385 research outputs found
Non-Holonomic Control IV : Coherence Protection in a Rubidium isotope
In this paper, we present a realistic application of the coherence protection
method proposed in the previous article. A qubit of information encoded on the
two spin states of a Rubidium isotope is protected from the action of electric
and magnetic fields
Non-Holonomic Control I
In this paper, we present a universal control technique, the non-holonomic
control, which allows us to impose any arbitrarily prescribed unitary evolution
to any quantum system through the alternate application of two well-chosen
perturbations
The host dark matter haloes of [O II] emitters at 0.5 < z < 1.5
Emission line galaxies (ELGs) are used in several ongoing and upcoming surveys (SDSS-IV/eBOSS, DESI) as tracers of the dark matter distribution. Using a new galaxy formation model, we explore the characteristics of [OII] emitters, which dominate optical ELG selections at z â 1. Model [OII] emitters at 0.5 < z < 1.5 are selected to mimic the DEEP2, VVDS, eBOSS and DESI surveys. The luminosity functions of model [OII] emitters are in reasonable agreement with observations. The selected [OII] emitters are hosted by haloes with Mhalo â„ 1010.3hâ1Mâ, with âŒ90âperâcent of them being central star-forming galaxies. The predicted mean halo occupation distributions of [OII] emitters have a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies, âšNâ©[OII]cenâ , being far from the canonical step function. The âšNâ©[OII]cen can be described as the sum of an asymmetric Gaussian for discs and a step function for spheroids, which plateau below unity. The model [OII] emitters have a clustering bias close to unity, which is below the expectations for eBOSS and DESI ELGs. At z ⌠1, a comparison with observed g-band-selected galaxy, which is expected to be dominated by [OII] emitters, indicates that our model produces too few [OII] emitters that are satellite galaxies. This suggests the need to revise our modelling of hot gas stripping in satellite galaxies
The host dark matter haloes of [O II] emitters at 0.5 < z < 1.5
Emission line galaxies (ELGs) are used in several ongoing and upcoming surveys (SDSS-IV/eBOSS, DESI) as tracers of the dark matter distribution. Using a new galaxy formation model, we explore the characteristics of [OII] emitters, which dominate optical ELG selections at z â 1. Model [OII] emitters at 0.5 < z < 1.5 are selected to mimic the DEEP2, VVDS, eBOSS and DESI surveys. The luminosity functions of model [OII] emitters are in reasonable agreement with observations. The selected [OII] emitters are hosted by haloes with Mhalo â„ 1010.3hâ1Mâ, with âŒ90âperâcent of them being central star-forming galaxies. The predicted mean halo occupation distributions of [OII] emitters have a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies, âšNâ©[OII]cenâ , being far from the canonical step function. The âšNâ©[OII]cen can be described as the sum of an asymmetric Gaussian for discs and a step function for spheroids, which plateau below unity. The model [OII] emitters have a clustering bias close to unity, which is below the expectations for eBOSS and DESI ELGs. At z ⌠1, a comparison with observed g-band-selected galaxy, which is expected to be dominated by [OII] emitters, indicates that our model produces too few [OII] emitters that are satellite galaxies. This suggests the need to revise our modelling of hot gas stripping in satellite galaxies
Annihilation of low energy antiprotons in silicon
The goal of the AEIS experiment at the Antiproton
Decelerator (AD) at CERN, is to measure directly the Earth's gravitational
acceleration on antimatter. To achieve this goal, the AEIS
collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a
velocity of a few 100 m/s and measure the magnitude of the vertical deflection
of the beam from a straight path. The final position of the falling
antihydrogen will be detected by a position sensitive detector. This detector
will consist of an active silicon part, where the annihilations take place,
followed by an emulsion part. Together, they allow to achieve 1 precision on
the measurement of with about 600 reconstructed and time tagged
annihilations.
We present here, to the best of our knowledge, the first direct measurement
of antiproton annihilation in a segmented silicon sensor, the first step
towards designing a position sensitive silicon detector for the
AEIS experiment. We also present a first comparison with
Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeVComment: 21 pages in total, 29 figures, 3 table
AEGIS at CERN: Measuring Antihydrogen Fall
The main goal of the AEGIS experiment at the CERN Antiproton Decelerator is
the test of fundamental laws such as the Weak Equivalence Principle (WEP) and
CPT symmetry. In the first phase of AEGIS, a beam of antihydrogen will be
formed whose fall in the gravitational field is measured in a Moire'
deflectometer; this will constitute the first test of the WEP with antimatter.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
The X-ray invisible Universe. A look into the halos undetected by eROSITA
The paper presents the analysis of GAMA spectroscopic groups and clusters
detected and undetected in the SRG/eROSITA X-ray map of the eFEDS (eROSITA
Final Equatorial Depth Survey) area, in the halo mass range
and at . We compare the X-ray surface brightness profiles
of the eROSITA detected groups with the mean stacked profile of the undetected
low-mass halos. Overall, we find that the undetected groups exhibit less
concentrated X-ray surface brightness, dark matter, and galaxy distributions
with respect to the X-ray detected halos. Consistently with the low mass
concentration, the magnitude gap indicates that these are younger systems. The
later assembly time is confirmed by the bluer average color of the BCG and of
the galaxy population with respect to the detected systems. They reside with a
higher probability in filaments while X-ray detected low-mass halos favor the
nodes of the Cosmic Web. Because of the suppressed X-ray central emission, the
undetected systems tend to be X-ray under-luminous at fixed halo mass, and to
lie below the relation. Interestingly, the X-ray detected
systems inhabiting the nodes scatter the less around the relation, while those
in filaments tend to lie below it. We do not observe any strong relation
between the properties of detected and undetected systems with the AGN
activity. The fraction of optically selected AGN in the galaxy population is
consistent in the two samples. More interestingly, the probability that the BCG
hosts a radio AGN is lower in the undetected groups. We, thus, argue that the
observed differences between X-ray detected and undetected groups are
ascribable to the Cosmic Web, and its role in the halo assembly bias. Our
results suggest that the X-ray selection is biased to favor the most
concentrated and old systems located in the nodes of the Cosmic Web.Comment: 15 pages, 13 figures, Submitted to MNRA
Prospects for measuring the gravitational free-fall of antihydrogen with emulsion detectors
The main goal of the AEgIS experiment at CERN is to test the weak equivalence
principle for antimatter. AEgIS will measure the free-fall of an antihydrogen
beam traversing a moir\'e deflectometer. The goal is to determine the
gravitational acceleration g for antihydrogen with an initial relative accuracy
of 1% by using an emulsion detector combined with a silicon micro-strip
detector to measure the time of flight. Nuclear emulsions can measure the
annihilation vertex of antihydrogen atoms with a precision of about 1 - 2
microns r.m.s. We present here results for emulsion detectors operated in
vacuum using low energy antiprotons from the CERN antiproton decelerator. We
compare with Monte Carlo simulations, and discuss the impact on the AEgIS
project.Comment: 20 pages, 16 figures, 3 table
- âŠ