Jan Ambjørn
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Jan Ambjørn
Jan Ambjørn is a Danish theoretical physicist. He received his PhD in 1980 at the Niels Bohr Institute in Copenhagen, followed by postdoctoral research positions at Caltech and Nordita. He has been employed at the Niels Bohr Institute from 1986, since 1992 as professor in theoretical physics.  From 2003 to 2010 he was also a professor at Utrecht University, and since 2012 he has been a professor at Radboud University, both in the Netherlands. Ambjørn has worked on a large number of different topics. As a PhD student he worked together with his adviser P. Olesen on understanding the vacuum structure of QCD, using a model called the Copenhagen Vacuum. Later they developed the theory of magnetism in the electroweak theory. It provides a very simple physical realisation of anti-screening, an effect associated with asymptotically free quantum field theories. Together with B. Durhuus and Jürg Fröhlich he proposed a non-perturbative formulation of the boson string theory, us ...
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Niels Bohr Institute
The Niels Bohr Institute (Danish: ''Niels Bohr Institutet'') is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics. Overview The institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr's birth – October 7, 1965 – the Institute officially became the Niels Bohr Institute. Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation. During the 1920s, and 1930s, the institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and ...
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Utrecht University
Utrecht University (UU; nl, Universiteit Utrecht, formerly ''Rijksuniversiteit Utrecht'') is a public research university in Utrecht, Netherlands. Established , it is one of the oldest universities in the Netherlands. In 2018, it had an enrollment of 31,801 students, and employed 7,191 faculty and staff. In 2018, 525 PhD degrees were awarded and 6,948 scientific articles were published. The 2018 budget of the university was €857 million. Utrecht University counts a number of distinguished scholars among its alumni and faculty, including 12 Nobel Prize laureates and 13 Spinoza Prize laureates. Utrecht University has been placed consistently in the top 100 universities in the world by prominent international ranking tables. The university is ranked as the best university in the Netherlands by the Shanghai Ranking of World Universities 2022, ranked 14th in Europe and 54th in the world. The university's motto is "Sol Iustitiae Illustra Nos", which means ''May the Sun of Righteous ...
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Radboud University
Radboud University (abbreviated as RU, nl, Radboud Universiteit , formerly ''Katholieke Universiteit Nijmegen'') is a public research university located in Nijmegen, the Netherlands. The university bears the name of Saint Radboud, a 9th century Dutch bishop who was known for his intellect and support of the underprivileged. Established in 1923, Radboud University has consistently been included in the top 150 of universities in the world by four major university ranking tables. As of 2020, it ranks 105th in the Shanghai Academic Ranking of World Universities. Internationally, RU is known for its strong research output. In 2020, 391 PhD degrees were awarded, and 8.396 scientific articles were published. To bolster the international exchange of academic knowledge, Radboud University joined the Guild of European Research-Intensive Universities in 2016. Among its alumni Radboud University counts 12 Spinoza Prize laureates and 1 Nobel Prize laureate, Sir Konstantin Novoselov, the disco ...
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Jürg Fröhlich
Jürg Martin Fröhlich (born 4 July 1946 in Schaffhausen) is a Swiss mathematician and theoretical physicist. He is best known for introducing rigorous techniques for the analysis of statistical mechanics models, in particular continuous symmetry breaking (infrared bounds), and for pioneering the study of topological phases of matter using low-energy effective field theories. Biography In 1965 Fröhlich began to study mathematics and physics at Eidgenössischen Technischen Hochschule Zürich. In 1969, under Klaus Hepp and Robert Schrader, he attained the Diplom (“Dressing Transformations in Quantum Field Theory”), and in 1972 he earned a PhD from the same institution under Klaus Hepp. After postdoctoral visits to the University of Geneva and Harvard University (with Arthur Jaffe), he took an assistant professorship in 1974 in the mathematics department of Princeton University. From 1978 until 1982 he was a professor at Institut des Hautes Études Scientifiques in Bu ...
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String Theory
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and interact with each other. On distance scales larger than the string scale, a string looks just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries the gravitational force. Thus, string theory is a theory of quantum gravity. String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and conde ...
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Quantum Gravity
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics; it deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vicinity of black holes or similar compact astrophysical objects, such as neutron stars. Three of the four fundamental forces of physics are described within the framework of quantum mechanics and quantum field theory. The current understanding of the fourth force, gravity, is based on Albert Einstein's general theory of relativity, which is formulated within the entirely different framework of classical physics. However, that description is incomplete: describing the gravitational field of a black hole in the general theory of relativity leads physical quantities, such as the spacetime curvature, to diverge at the center of the black hole. This signals the breakdown of the general theory of relativity and the need for a theory that goes b ...
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Hausdorff Dimension
In mathematics, Hausdorff dimension is a measure of ''roughness'', or more specifically, fractal dimension, that was first introduced in 1918 by mathematician Felix Hausdorff. For instance, the Hausdorff dimension of a single point is zero, of a line segment is 1, of a square is 2, and of a cube is 3. That is, for sets of points that define a smooth shape or a shape that has a small number of corners—the shapes of traditional geometry and science—the Hausdorff dimension is an integer agreeing with the usual sense of dimension, also known as the topological dimension. However, formulas have also been developed that allow calculation of the dimension of other less simple objects, where, solely on the basis of their properties of scaling and self-similarity, one is led to the conclusion that particular objects—including fractals—have non-integer Hausdorff dimensions. Because of the significant technical advances made by Abram Samoilovitch Besicovitch allowing computation of di ...
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Renate Loll
Renate Loll (born 19 June 1962, Aachen) is a Professor in Theoretical Physics at the Institute for Mathematics, Astrophysics and Particle Physics of the Radboud University in Nijmegen, Netherlands. She previously worked at the Institute for Theoretical Physics of Utrecht University. She received her Ph.D. from Imperial College, London, in 1989. In 2001 she joined the permanent staff of the ITP, after spending several years at the Max Planck Institute for Gravitational Physics in Golm, Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe .... With Jan Ambjørn and Polish physicist Jerzy Jurkiewicz she helped develop a new approach to nonperturbative quantization of gravity, that of Causal Dynamical Triangulations. She has been a member of the Royal Netherlands Academy o ...
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Causal Dynamical Triangulation
Causal dynamical triangulation (abbreviated as CDT) theorized by Renate Loll, Jan Ambjørn and Jerzy Jurkiewicz, is an approach to quantum gravity that, like loop quantum gravity, is background independent. This means that it does not assume any pre-existing arena (dimensional space), but rather attempts to show how the spacetime fabric itself evolves. There is evidence that at large scales CDT approximates the familiar 4-dimensional spacetime, but shows spacetime to be 2-dimensional near the Planck scale, and reveals a fractal structure on slices of constant time. These interesting results agree with the findings of Lauscher and Reuter, who use an approach called Quantum Einstein Gravity, and with other recent theoretical work. Introduction Near the Planck scale, the structure of spacetime itself is supposed to be constantly changing due to quantum fluctuations and topological fluctuations. CDT theory uses a triangulation process which varies dynamically an ...
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21st-century Danish Physicists
The 1st century was the century spanning AD 1 (Roman numerals, I) through AD 100 (Roman numerals, C) according to the Julian calendar. It is often written as the or to distinguish it from the 1st century BC (or BCE) which preceded it. The 1st century is considered part of the Classical era, epoch, or History by period, historical period. The 1st century also saw the Christianity in the 1st century, appearance of Christianity. During this period, Europe, North Africa and the Near East fell under increasing domination by the Roman Empire, which continued expanding, most notably conquering Britain under the emperor Claudius (AD 43). The reforms introduced by Augustus during his long reign stabilized the empire after the turmoil of the previous century's civil wars. Later in the century the Julio-Claudian dynasty, which had been founded by Augustus, came to an end with the suicide of Nero in AD 68. There followed the famous Year of Four Emperors, a brief period of civil war and inst ...
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Living People
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