168 research outputs found
The Free Will Theorem
On the basis of three physical axioms, we prove that if the choice of a
particular type of spin 1 experiment is not a function of the information
accessible to the experimenters, then its outcome is equally not a function of
the information accessible to the particles. We show that this result is
robust, and deduce that neither hidden variable theories nor mechanisms of the
GRW type for wave function collapse can be made relativistic. We also establish
the consistency of our axioms and discuss the philosophical implications.Comment: 31 pages, 6figure
SkÀrgÄrd 40 Är
SkÀrgÄrd 40 Är
â Inledaren: 40 Ă„r av Nina Söderlund
â SkĂ€rgĂ„rden som politisk passion av Stefan Wallin
â VĂ€rldsunika Ăsterbottens skĂ€rgĂ„rd av Olav Jern
â Med 40 Ă„rs perspektiv pĂ„ skĂ€rgĂ„rdsforskning av Nina Söderlund
â Femton Ă„r med tidskriften SkĂ€rgĂ„rd av HĂ„kan Eklund
â Inspirerande vattenskap av Cecilia Lundberg
â Karlö â en pĂ€rla lĂ€ngst i norr av Pia Prost
â Ett gott liv â tankar om att leva och överleva i skĂ€rgĂ„rden av Ester Miiros-Hollsten
â Ăn dĂ€r 130 000 fĂ„r har rumpan Ă„t samma hĂ„ll av John Wrede, Micaela Jansson och Pia Prost
â Utlandsröster: Kan du bli gammal pĂ„ din ö? av Dorthe Winther
â SkĂ€rgĂ„rdsfotograf Ralf Nikander
â SkĂ€rinytt
Bokhörnan:
â âDĂ€r stalp en igen!â av Nina Söderlund
â Ett fartygs livshistoria av Kristin Mattsson
â Sista bilde
Catching Element Formation In The Act
Gamma-ray astronomy explores the most energetic photons in nature to address
some of the most pressing puzzles in contemporary astrophysics. It encompasses
a wide range of objects and phenomena: stars, supernovae, novae, neutron stars,
stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays
and relativistic-particle acceleration, and the evolution of galaxies. MeV
gamma-rays provide a unique probe of nuclear processes in astronomy, directly
measuring radioactive decay, nuclear de-excitation, and positron annihilation.
The substantial information carried by gamma-ray photons allows us to see
deeper into these objects, the bulk of the power is often emitted at gamma-ray
energies, and radioactivity provides a natural physical clock that adds unique
information. New science will be driven by time-domain population studies at
gamma-ray energies. This science is enabled by next-generation gamma-ray
instruments with one to two orders of magnitude better sensitivity, larger sky
coverage, and faster cadence than all previous gamma-ray instruments. This
transformative capability permits: (a) the accurate identification of the
gamma-ray emitting objects and correlations with observations taken at other
wavelengths and with other messengers; (b) construction of new gamma-ray maps
of the Milky Way and other nearby galaxies where extended regions are
distinguished from point sources; and (c) considerable serendipitous science of
scarce events -- nearby neutron star mergers, for example. Advances in
technology push the performance of new gamma-ray instruments to address a wide
set of astrophysical questions.Comment: 14 pages including 3 figure
Fiskaren och fisken
Fiskaren och fisken
InnehÄllsförteckning
â Inledaren: Ett försvinnande kulturarv av Pia Prost
â VĂ€lmĂ„ende skĂ€rgĂ„rd tack vare strömmingen av Anne Bergström
â Vinternotdragningen â sörjd, saknad av Nina Söderlund
â Nationella och internationella bestĂ€mmelser kring fiske av Kaj Mattsson
â 130 Ă„r av fiskerirĂ„dgivning av Malin Lönnroth
â Sista Sibbofiskaren satsar pĂ„ förĂ€dling av Thure Malmberg
â Fisket i SkĂ€rgĂ„rdshavet i konstant förĂ€ndring av Pekka Salmi, Kristina Svels och Jari SetĂ€lĂ€
â Ett arbetsliv i fiskenĂ€ringens tjĂ€nst â Kari Ranta-aho gĂ„r i pension av Pia Prost
â Inhemskt fiskfoder bra för bĂ„de fiskerinĂ€ringen och havet av Pia Prost
â Vasa fick sitt Fiskets hus av Guy SvanbĂ€ck
â Förlorar vi en primĂ€rnĂ€ring? av Kaj Mattsson
â Konkurrens om fisken â mĂ€nniska, sĂ€l och skarv av Sture Hansson
â Allt hĂ€nger pĂ„ en god fiskeförvaltning av Cecilia Lundberg
â Aktuell fiskforskning vid Ă
bo Akademi av Martin Snickars och Tom Wiklund
â Historiska hamnplatser och fiskelĂ€gen kartlĂ€ggs av Tapani Tuovinen och Riikka Tevali
â GrĂ„sĂ€len Ă€r kustfiskets gissel av Mia Henriksson
â Hur uppfattar fiskarna sin omvĂ€rld? av Marina Saanila
Bokhörnan:
â GĂ€ddan, Nordens krokodil av Nalle Valtiala
â Ă
levangeliet: berÀttelsen om vÀrldens mest gÄtfulla fisk av Cecilia Lundberg
â Ăr Ă
land skÀrgÄrdssamhÀllenas paradis? av John Wrede
â SkĂ€rgĂ„rden diskuterade FN:s hĂ„llbarhetsmĂ„l av Pia Prost
â SkĂ€rinytt
â Sista bilde
Three-year performance of the IceAct telescopes at the IceCube Neutrino Observatory
IceAct is an array of compact Imaging Air Cherenkov Telescopes at the ice surface as part of the IceCube Neutrino Observatory. The telescopes, featuring a camera of 61 silicon photomultipliers and fresnel-lens-based optics, are optimized to be operated in harsh environmental conditions, such as at the South Pole. Since 2019, the first two telescopes have been operating in a stereoscopic configuration in the center of IceCube\u27s surface detector IceTop. With an energy threshold of about 10 TeV and a wide field-of-view, the IceAct telescopes show promising capabilities of improving current cosmic-ray composition studies: measuring the Cherenkov light emissions in the atmosphere adds new information about the shower development not accessible with the current detectors. First simulations indicate that the added information of a single telescope leads, e.g., to an improved discrimination between flux contributions from different primary particle species in the sensitive energy range.
We review the performance and detector operations of the telescopes during the past 3 years (2020-2022) and give an outlook on the future of IceAct
In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory
The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p
Mechanical design of the optical modules intended for IceCube-Gen2
IceCube-Gen2 is an expansion of the IceCube neutrino observatory at the South Pole that aims to increase the sensitivity to high-energy neutrinos by an order of magnitude. To this end, about 10,000 new optical modules will be installed, instrumenting a fiducial volume of about 8 km3. Two newly developed optical module types increase IceCubeâs current sensitivity per module by a factor of three by integrating 16 and 18 newly developed four-inch PMTs in specially designed 12.5-inch diameter pressure vessels. Both designs use conical silicone gel pads to optically couple the PMTs to the pressure vessel to increase photon collection efficiency. The outside portion of gel pads are pre-cast onto each PMT prior to integration, while the interiors are filled and cast after the PMT assemblies are installed in the pressure vessel via a pushing mechanism. This paper presents both the mechanical design, as well as the performance of prototype modules at high pressure (70 MPa) and low temperature (â40âC), characteristic of the environment inside the South Pole ice
In situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory
The IceCube Neutrino Observatory instruments about 1âkm3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. We examine birefringent light propagation through the polycrystalline ice microstructure as a possible explanation for this effect. The predictions of a first-principles model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties include not only the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube light-emitting diode (LED) calibration data, the theory and parameterization of the birefringence effect, the fitting procedures of these parameterizations to experimental data, and the inferred crystal properties.Peer Reviewe
The next generation neutrino telescope: IceCube-Gen2
The IceCube Neutrino Observatory, a cubic-kilometer-scale neutrino detector at the geographic South Pole, has reached a number of milestones in the field of neutrino astrophysics: the discovery of a high-energy astrophysical neutrino flux, the temporal and directional correlation of neutrinos with a flaring blazar, and a steady emission of neutrinos from the direction of an active galaxy of a Seyfert II type and the Milky Way. The next generation neutrino telescope, IceCube-Gen2, currently under development, will consist of three essential components: an array of about 10,000 optical sensors, embedded within approximately 8 cubic kilometers of ice, for detecting neutrinos with energies of TeV and above, with a sensitivity five times greater than that of IceCube; a surface array with scintillation panels and radio antennas targeting air showers; and buried radio antennas distributed over an area of more than 400 square kilometers to significantly enhance the sensitivity of detecting neutrino sources beyond EeV. This contribution describes the design and status of IceCube-Gen2 and discusses the expected sensitivity from the simulations of the optical, surface, and radio components
Sensitivity of IceCube-Gen2 to measure flavor composition of Astrophysical neutrinos
The observation of an astrophysical neutrino flux in IceCube and its detection capability to separate between the different neutrino flavors has led IceCube to constraint the flavor content of this flux. IceCube-Gen2 is the planned extension of the current IceCube detector, which will be about 8 times larger than the current instrumented volume. In this work, we study the sensitivity of IceCube-Gen2 to the astrophysical neutrino flavor composition and investigate its tau neutrino identification capabilities. We apply the IceCube analysis on a simulated IceCube-Gen2 dataset that mimics the High Energy Starting Event (HESE) classification. Reconstructions are performed using sensors that have 3 times higher quantum efficiency and isotropic angular acceptance compared to the current IceCube optical modules. We present the projected sensitivity for 10 years of data on constraining the flavor ratio of the astrophysical neutrino flux at Earth by IceCube-Gen2
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