664 research outputs found
Second-order electronic correlation effects in a one-dimensional metal
The Pariser-Parr-Pople (PPP) model of a single-band one-dimensional (1D)
metal is studied at the Hartree-Fock level, and by using the second-order
perturbation theory of the electronic correlation. The PPP model provides an
extension of the Hubbard model by properly accounting for the long-range
character of the electron-electron repulsion. Both finite and infinite version
of the 1D-metal model are considered within the PPP and Hubbard approximations.
Calculated are the second-order electronic-correlation corrections to the total
energy, and to the electronic-energy bands. Our results for the PPP model of 1D
metal show qualitative similarity to the coupled-cluster results for the 3D
electron-gas model. The picture of the 1D-metal model that emerges from the
present study provides a support for the hypothesis that the normal metallic
state of the 1D metal is different from the ground state.Comment: 21 pages, 16 figures; v2: small correction in title, added 3
references, extended and reformulated a few paragraphs (detailed information
at the end of .tex file); added color to figure
Cherenkov Telescope Array Data Management
Very High Energy gamma-ray astronomy with the Cherenkov Telescope Array (CTA)
is evolving towards the model of a public observatory. Handling, processing and
archiving the large amount of data generated by the CTA instruments and
delivering scientific products are some of the challenges in designing the CTA
Data Management. The participation of scientists from within CTA Consortium and
from the greater worldwide scientific community necessitates a sophisticated
scientific analysis system capable of providing unified and efficient user
access to data, software and computing resources. Data Management is designed
to respond to three main issues: (i) the treatment and flow of data from remote
telescopes; (ii) "big-data" archiving and processing; (iii) and open data
access. In this communication the overall technical design of the CTA Data
Management, current major developments and prototypes are presented.Comment: 8 pages, 2 figures, In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
The Drift Chambers Of The Nomad Experiment
We present a detailed description of the drift chambers used as an active
target and a tracking device in the NOMAD experiment at CERN. The main
characteristics of these chambers are a large area, a self supporting structure
made of light composite materials and a low cost. A spatial resolution of 150
microns has been achieved with a single hit efficiency of 97%.Comment: 42 pages, 26 figure
Copper alloys in investment casting technology
This paper presents research results in the field of casting technology of copper and copper alloys using the investment casting technology, both from historical as well as modern technology perspective. The analysis of exemplary elements of the old casting moulds is included, as well as the Bronze Age casts. The chemical content of various copper alloys was determined and the application of lost wax method was confirmed in the Bronze Age workshop. At present, investment casting method is used for manufacturing high-quality casts, especially products for power engineering that is why it demands respecting very rigorous technological requirements. The casts were characterised based on microstructure research, chemical composition and conductivity in relation to oxygen content
All-sky Search for High-Energy Neutrinos from Gravitational Wave Event GW170104 with the ANTARES Neutrino Telescope
Advanced LIGO detected a significant gravitational wave signal (GW170104)
originating from the coalescence of two black holes during the second
observation run on January 4, 2017. An all-sky high-energy
neutrino follow-up search has been made using data from the ANTARES neutrino
telescope, including both upgoing and downgoing events in two separate
analyses. No neutrino candidates were found within s around the GW
event time nor any time clustering of events over an extended time window of
months. The non-detection is used to constrain isotropic-equivalent
high-energy neutrino emission from GW170104 to less than
erg for a spectrum
The Antares Collaboration : Contributions to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague)
The ANTARES detector, completed in 2008, is the largest neutrino telescope in the Northern hemisphere. Located at a depth of 2.5 km in the Mediterranean Sea, 40 km off the Toulon shore, its main goal is the search for astrophysical high energy neutrinos. In this paper we collect the 21 contributions of the ANTARES collaboration to the 34th International Cosmic Ray Conference (ICRC 2015). The scientific output is very rich and the contributions included in these proceedings cover the main physics results, ranging from steady point sources, diffuse searches, multi-messenger analyses to exotic physics
The ANTARES Collaboration: Contributions to ICRC 2017 Part I: Neutrino astronomy (diffuse fluxes and point sources)
Papers on neutrino astronomy (diffuse fluxes and point sources, prepared for
the 35th International Cosmic Ray Conference (ICRC 2017, Busan, South Korea) by
the ANTARES Collaboratio
The ANTARES Collaboration: Contributions to ICRC 2017 Part III: Searches for dark matter and exotics, neutrino oscillations and detector calibration
Papers on the searches for dark matter and exotics, neutrino oscillations and
detector calibration, prepared for the 35th International Cosmic Ray Conference
(ICRC 2017, Busan, South Korea) by the ANTARES Collaboratio
The ANTARES Collaboration: Contributions to ICRC 2017 Part II: The multi-messenger program
Papers on the ANTARES multi-messenger program, prepared for the 35th
International Cosmic Ray Conference (ICRC 2017, Busan, South Korea) by the
ANTARES Collaboratio
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