189,834 research outputs found
Towards apparent convergence in asymptotically safe quantum gravity
The asymptotic safety scenario in gravity is accessed within the systematic
vertex expansion scheme for functional renormalisation group flows put forward
in \cite{Christiansen:2012rx,Christiansen:2014raa}, and implemented in
\cite{Christiansen:2015rva} for propagators and three-point functions. In the
present work this expansion scheme is extended to the dynamical graviton
four-point function. For the first time, this provides us with a closed flow
equation for the graviton propagator: all vertices and propagators involved are
computed from their own flows.
In terms of a covariant operator expansion the current approximation gives
access to , , as well as and higher derivative
operators. We find a UV fixed point with three attractive and two repulsive
directions, thus confirming previous studies on the relevance of the first
three operators. In the infrared we find trajectories that correspond to
classical general relativity and further show non-classical behaviour in some
fluctuation couplings.
We also find signatures for the apparent convergence of the systematic vertex
expansion. This opens a promising path towards establishing asymptotically safe
gravity in terms of apparent convergence.Comment: 24 pages, 6 figures; journal version with updated reference
Wilbur Norman Christiansen 1913-2007
W. N. ('Chris') Christiansen was an innovative and influential radio
astronomy pioneer. The hallmarks of his long and distinguished career in
science and engineering, spanning almost five decades, were his inventiveness
and his commitment to, and success with, large-scale projects. These projects
were the outcome of his innovative skill as physicist and engineer. Paralleling
this was his equal commitment to forging strong international links and
friendships, leading to his election as Vice-President of the International
Astronomical Union for the years 1964 to 1970, as President of the
International Union of Radio Science, URSI, from 1978 to 1981, and subsequently
as Honorary Life President in 1984, and as Foreign Secretary of the Australian
Academy of Science from 1981 to 1985. Major subsequent developments in radio
astronomy and wireless communications on the global scene stand as a legacy to
Chris's approach to his work and to the development of those who worked with
him.Comment: 16 pages, 4 figure
Newspaper Critic Shapes Chicago Style of Theater
This study of coverage of the local theater scene from 1975–85 in three Chicago dailies found that one critic, Richard Christiansen, had the strongest influence on the development of the Chicago Style that flourished in the off-Loop theaters. </jats:p
Wind engineering study of One Williams Center, Tulsa
CER74-75JAP-JEC25.Includes bibliographical references.December 1974.For Skilling, Helle, Christiansen and Robertson.Supported by Skilling, Helle, Christiansen and Robertson
Byron Child Christiansen and Merrilee Christiansen, husband and wife v. Farmers Insurance Exchange : Brief of Appellee
BRIEF OF PLAINTIFFS/APELLEES BYRON CHILD CHRISTIANSEN AND MERRILEE CHRISTIANSEN ON THE INTERLOCUTORY APPEAL FROM THE THIRD DISTRICT COURT, HONORABLE JOSEPH C. FRATTO, JR
A commentary on "The now-or-never bottleneck: a fundamental constraint on language", by Christiansen and Chater (2016)
In a recent article, Christiansen and Chater (2016) present a fundamental
constraint on language, i.e. a now-or-never bottleneck that arises from our
fleeting memory, and explore its implications, e.g., chunk-and-pass processing,
outlining a framework that promises to unify different areas of research. Here
we explore additional support for this constraint and suggest further
connections from quantitative linguistics and information theory
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