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Copenhagen, Czech Republic

The Niels Bohr Institute is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.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 often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute. Wikipedia.

Boels R.H.,Niels Bohr Institute
Journal of High Energy Physics | Year: 2010

Maximally supersymmetric gauge theory in four dimensions has a remarkably simple S-matrix at the origin of its moduli space at both tree and loop level. This leads to the question what, if any, of this structure survives at the complement of this one point. Here this question is studied in detail at one loop for the branch of the moduli space parameterized by a vacuum expectation value for one complex scalar. Motivated by the parallel D-brane picture of spontaneous symmetry breaking a simple relation is demonstrated between the Lagrangian of broken super Yang-Mills theory and that of its higher dimensional unbroken cousin. Using this relation it is proven both through an on-as well as an off-shell method there are no so-called triangle coefficients in the natural basis of one-loop functions at any finite point of the moduli space for the theory under study. The off-shell method yields in addition absence of rational terms in a class of theories on the Coulomb branch which includes the special case of maximal supersymmetry. The results in this article provide direct field theory evidence for a recently proposed exact dual conformal symmetry motivated by the AdS/CFT correspondence. © SISSA 2010.

Boels R.,Niels Bohr Institute
Journal of High Energy Physics | Year: 2010

There has been substantial calculational progress in the last few years for gauge theory amplitudes which involve massless four dimensional particles. One of the central ingredients in this has been the ability to keep precise track of the Poincaré algebra quantum numbers of the particles involved. Technically, this is most easily done using the well-known four dimensional spinor helicity method. In this article a natural generalization to all dimensions higher than four is obtained based on a covariant version of the representation theory of the Poincaré algebra. Covariant expressions for all possible polarization states, both bosonic and fermionic, are constructed. For the fermionic states the analysis leads directly to pure spinors. The natural extension to the representation theory of the on-shell supersymmetry algebra results in an elementary derivation of the supersymmetry Ward identities for scattering amplitudes with massless or massive legs in any integer dimension from four onwards. As a proof-of-concept application a higher dimensional analog of the vanishing helicity-equal amplitudes in four dimensions is presented in (super) Yang-Mills theory, Einstein (super-)gravity and superstring theory in a flat background. © SISSA 2010.

Denney K.D.,Niels Bohr Institute
Astrophysical Journal | Year: 2012

We use a combination of reverberation mapping data and single-epoch (SE) spectra of the C IV emission line in a sample of both low- and high-redshift active galactic nuclei to investigate sources of the discrepancies between C IV- and Hβ-based SE black hole (BH) mass estimates. We find that for all reverberation mapped sources, there is a component of the line profile that does not reverberate, and the velocity characteristics of this component vary from object to object. The differing strength and properties of this non-variable component are responsible for much of the scatter in C IV-based BH masses compared to Hβ masses. The C IV mass bias introduced by this non-variable component is correlated with the shape of the C IV line, allowing us to make an empirical correction to the BH mass estimates. Using this correction and accounting for other sources of scatter, such as poor data quality and data inhomogeneity, reduces the scatter between the C IV and Hβ masses in our sample by a factor of ∼2, to only ∼0.2dex. We discuss the possibility that this non-variable C IV component originates in an orientation-dependent outflow from either the proposed broad-line region disk wind or the intermediate-line region, a high-velocity inner extension of the narrow-line region. © 2012. The American Astronomical Society. All rights reserved.

We report on the measurement of various flow harmonics, vn, with multi-particle cumulants, and present the results from a study of the inter-correlation among different order symmetry planes Ψn via multi-particle mixed harmonic correlations. This provides comprehensive experimental information on the fluctuating event-by-event shape of the initial conditions, which is currently among the main sources of large theoretical uncertainties in describing the evolution of the system created in heavy-ion collisions. © 2013 CERN.

Zoubos K.,Niels Bohr Institute
Letters in Mathematical Physics | Year: 2012

We review the role of integrability in the planar spectral problem of four-dimensional superconformal gauge theories besides N = 4 SYM. The cases considered include the Leigh-Strassler marginal deformations of N = 4 SYM, quiver theories which arise as orbifolds of AdS 5 × S 5 on the dual gravity side, as well as various theories involving open spin chains. © 2011 Springer.

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