scholarly journals Acceleration-Induced Nonlocality

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
World Line ◽  
Integral Relation ◽  
Field Measurements ◽  
Physical Principle ◽  
Relativity Theory ◽  
General Integral ◽  
Electric And Magnetic Fields ◽  
The Status ◽  
Classical Point Particles ◽  
Classical Point

The locality postulate of the standard relativity theory is exact when dealing with phenomena involving classical point particles and rays of radiation, but breaks down for electromagnetic fields, as field properties cannot be measured instantaneously. Furthermore, Bohr and Rosenfeld pointed out in 1933 that only spacetime averages of the classical electric and magnetic fields have immediate physical significance. This assertion acquires the status of a physical principle when the intrinsic acceleration scales of observers are taken into account. To incorporate acceleration-induced nonlocality into relativity theory, a general integral relation is postulated between the field as measured by an accelerated observer and the instantaneous field measurements of the momentarily comoving inertial observers along the past world line of the observer. This nonlocal ansatz involves an acceleration kernel and leads to nonlocal special relativity once the kernel is determined.

Statistical Mechanics of Classical Particles with Gravitational Interactions: Exactly Solvable (for N≤∞) in d=1 and d>2

1997 ◽  
Vol 11 (01n02) ◽  
pp. 127-131 ◽  
Author(s):  
Michael K.-H. Kiessling
Keyword(s):  
Statistical Mechanics ◽  
Continuum Model ◽  
Exactly Solvable Models ◽  
Solvable Models ◽  
Point Particles ◽  
Exactly Solvable ◽  
Classical Point Particles ◽  
Classical Particles ◽  
Classical Point ◽  
Liouville’S Equation

This paper is concerned with a curious gap in a string of exactly solvable models, a gap that is suggestively related to a completely integrable nonlinear PDE in d=2 known as Liouville's equation. This PDE emerges in a limit N→∞ from the equilibrium statistical mechanics of classical point particles with gravitational interactions (SMGI) in dimension d=2 which, accordingly, is an exactly solvable continuum model in this limit. Interestingly, in d=1 and all d>2, the SMGI can be, and partly has been, exactly evaluated for all N≤∞. This entitles one to suspect that the SMGI for d=2 is likewise exactly solvable for N>∞, but currently this is an unproven hypothesis. If this conjecture can be answered in the affirmative, spin-offs in various areas associated with Liouville's equation, such as vortex gases, superfluidity, random matrices, and string theory can be expected.

scholarly journals Physical and Wind Properties of OB-Stars

2007 ◽  
Vol 3 (S250) ◽  
pp. 25-38 ◽  
Author(s):  
Joachim Puls
Keyword(s):  
Magnetic Field ◽  
Spectral Type ◽  
Massive Stars ◽  
Field Measurements ◽  
Status Quo ◽  
Observational Constraints ◽  
Ob Stars ◽  
Magnetic Field Measurements ◽  
The Status ◽  
Weak Winds

AbstractIn this review, the physical and wind properties of OB-stars are discussed, with particular emphasis on metallicity dependence and recent results from the flames survey of massive stars. We summarize the relation between spectral type and Teff, discuss the status quo of the “mass-discrepancy”, refer to the problem of “macro-turbulence” and comment on the distribution of rotational velocities. Observational constraints on the efficiency of rotational mixing are presented, and magnetic field measurements summarized. Wind properties are reviewed, and problems related to weak winds and wind-clumping highlighted.

scholarly journals Flood risk assessment and cultural heritage impact in the Instituto Superior de Arte (ISA) in Habana.

2020 ◽  
Author(s):  
Daniele Fabrizio Bignami ◽  
Leonardo Stucchi ◽  
Daniele Bocchiola ◽  
Christian Zecchin ◽  
Davide Del Curto ◽  
...  
Keyword(s):  
Flood Risk ◽  
Laser Scanner ◽  
Drainage System ◽  
Digital Terrain Model ◽  
Field Measurements ◽  
Point Of View ◽  
Discharge Data ◽  
Terrain Model ◽  
Critical Discharge ◽  
The Status

<p>Keeping ISA Modern is a project of Fondazione Politecnico di Milano and other partners aimed at planning the conservation of some of the buildings (Schools) of the University of Arts (ISA) of Cuba, built over a former country club, designed by eminent architects of the time (Vittorio Garatti, Roberto Gottardi and Ricardo Porro), and bestowed with the status of UNESCO World Heritage in 2003.</p><p>Most of the Schools are currently unusable, also due to damages caused by frequent floods from the surrounding Rio Quibù river, and they need urgent restoration if they are to be used. Personnel of Politecnico di Milano carried out a field survey on the Rio Quibù during 2019, and also based upon information from the Cuban National Institute of Hydraulic Resources (INRH) they studied established flood risk for ISA.</p><p>Here, we built a high-resolution digital terrain model (DTM) of the park where Schools are located, using laser scanner data, and previously georeferenced points. Using field measurements taken in June 2019 we were able to assess geometry (included bridges), slope and roughness coefficients of the main channel of the Quibù river, influence of the sea level. Then using as input critical discharge data provided by INRH we evaluated flood area and flood volume for 4 representative return periods (5, 20, 50, 100 years).</p><p>The most impacted building is the School of Ballet, located within a narrow meander of Rio Quibù, immediately upstream of a narrow bridge, clogging largely during floods, only 1 km far from the sea, and with drainage system unable to discharge storm water.</p><p>Given the high required cost, a partially collapsed wall originally partially protecting the School of Ballet was not rebuilt, and we are now exploring flood mitigation strategy which are cheaper, and feasible from the point of view of compatibility with the historical and architectural value of the building.</p>

The status of cattle genetic resources in North Ethiopia: On-farm characterization of six major cattle breeds

2007 ◽  
Vol 40 ◽  
pp. 15-32 ◽  
Author(s):  
M. Zerabruk ◽  
O. Vangen ◽  
M. Haile
Keyword(s):  
Production Systems ◽  
Field Measurements ◽  
The Other ◽  
Current Status ◽  
Cattle Breeds ◽  
Mixed Crop ◽  
The Status ◽  
Study Population ◽  
Secondary Information ◽  
On Farm

SummaryOn-farm surveys and characterisation of six indigenous north Ethiopian cattle breeds (Afar, Arado, Begait, Fogera, Medenes and Raya) was carried out with the objective of determining the current status of these breeds. Information from a structured questionnaire distributed to 450 farmers, 37 group discussions, field measurements of heart girth and height on 25 males and 25 females from each breed and secondary information were used to carry out the study. Population size of the Arado breed increased by more than three fold between 1992 and 1999, while the Raya, Fogera and Begait population decreased by57, 27 and 67%; between 1981 and 1999 respectively. Three distinctive types were identified within the Afar and Begait breeds with different adaptation and threat levels in relation to changes to the bio-physical and social environment. Overall production and reproduction performance of the breeds in the pastoral production system (Afar and Begait) was higher than the Raya and Medenes, and Arado and Fogera breeds of the agro-pastoral and mixed crop/livestock production systems respectively. Extinction probability for most ofthe breeds was high, the highest (0.67) being for the Begait breed. On the other hand, except for the initiative taken to evaluate, improve and conserve the Fogera breed at the Metekel and Andasa cattle breeding ranches, there are no institutionalized attempts towards improving and/or conserving the other breeds.

Electromagnetic (self-) interactions in relativistic Schrödinger theory

2001 ◽  
Vol 79 (6) ◽  
pp. 879-906
Author(s):  
M Mattes ◽  
S Rupp ◽  
M Sorg
Keyword(s):  
Gauge Field ◽  
Mathematical Structure ◽  
Point Particle ◽  
Pathological Features ◽  
Fibre Bundles ◽  
Point Particles ◽  
Self Energy ◽  
Electromagnetic Interactions ◽  
Classical Point Particles ◽  
Classical Point

The Relativistic Schrödinger Theory (RST) is applied to a system of N particles with electromagnetic interactions. The gauge group is U(1) × U(1)... × U(1). By exploiting the mathematical structure of fibre bundles, the energy-momentum content of the gauge field can be defined in such a way that no infinite self-energy of point charges can arise. However, the picture of classical point particles becomes insufficient in any case in view of the exchange and overlap effects occurring in RST. The presence of overlap currents seems to be necessary to remedy certain pathological features of the classical point-particle theories. PACS Nos.: 03.65Pm, 03.65Ge, 03.65Ta

scholarly journals Credulous Modellers and Suspicious Experimentalists? Comparison of Model Output and Data in Meteorological Simulation Modelling

2006 ◽  
Vol 19 (1) ◽  
pp. 52-68
Author(s):  
Mikaela Sundberg
Keyword(s):  
Field Measurements ◽  
Simulation Modelling ◽  
Theory Model ◽  
Observation Data ◽  
Model Output ◽  
Trouble Shooting ◽  
The Status ◽  
Working Practices ◽  
Meteorological Simulation ◽  
The Relationship

This article studies the relation between two specialised practices in meteorology, modelling and field measurements. This relation is embodied in a number of joint practices of which model evaluation is one of them. The relationship between theory, model and observation has been of concern for many philosophers of science whereas the relationship between the working practices that underlie theories, models and observations, has received less attention. This paper describes and compares the practices that generate observation data and model output and the way different roles that fieldworkers and modellers have in this process are established. Next, different practice-oriented perspectives on the status of models, data and experiments are analysed and the discussion then moves on to the different trouble-shooting strategies scientists deploy, depending on their position within the discipline. It is shown that these strategies are often based on the ideas and judgements that modellers and experimentalists express about each other, and by implication, about their own role in the meteorological enterprise.

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