111 research outputs found
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
Minimal Length Scale Scenarios for Quantum Gravity
We review the question of whether the fundamental laws of nature limit our
ability to probe arbitrarily short distances. First, we examine what insights
can be gained from thought experiments for probes of shortest distances, and
summarize what can be learned from different approaches to a theory of quantum
gravity. Then we discuss some models that have been developed to implement a
minimal length scale in quantum mechanics and quantum field theory. These
models have entered the literature as the generalized uncertainty principle or
the modified dispersion relation, and have allowed the study of the effects of
a minimal length scale in quantum mechanics, quantum electrodynamics,
thermodynamics, black-hole physics and cosmology. Finally, we touch upon the
question of ways to circumvent the manifestation of a minimal length scale in
short-distance physics.Comment: Published version available at
http://www.livingreviews.org/lrr-2013-
Über den Zusammenhang zwischen Intensität, Polarisation und Ablenkungswinkel bei der Ramanstrahlung
Sur les propriétés périodiques des noyaux atomiques
On montre ici théoriquement, à partir de quelques hypothèses simples, que les noyaux de propriétés physiques analogues peuvent avoir des poids atomiques de valeurs suivantes : 1, 8, 21, 64, 125 et 216. L'existence d'une loi périodique gouvernant les propriétés des noyaux est aussi probable. D'ailleurs la périodicité indiquée peut être prouvée par des faits expérimentaux. Le nombre des électrons dans le noyau, les nombres des isotopes de même poids atomique, la loi de Harkins et la radioactivité indiquent une périodicité qui s'accorde avec la théorie
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