ELFT HÍRADÓ

["Szabados,L." <lbszab AT rmki.kfki.hu>]

RELATIVITASELMELETI SZEMINARIUM


Eloado:  Prof Osvaldo Moreschi
         Univ. Nac. de Córdoba, Argentina

Az eloadas cime: Unambiguous notion of total intrinsic angular momentum
                 in general relativity

t:       2013 julius 15 (hetfo), 14.00
(x,y,z): KFKI RMKI III. epulet, tanacsterem

Kivonat:

The notion of total angular momentum at future null infinity has been 
the subject of numerous works. Different author have employed a variety of 
approaches that yielded nonequivalent definitions.

The key problem at future null infinity is that the symmetry group is 
not the ten dimensional Poincare group, but the infinite dimensional BMS 
group. This in turn leads to the problem of supertranslation ambiguities.
Almost all of the suggested definitions, for the general case, suffer 
from the so called problem of supertranslations. However, in the past we 
have provided with a definition of intrinsic angular momentum which have 
circumvented those problems and also provided at the same time with the 
notion of center of mass at future null infinity. This approach was based 
on the notion of charge integrals of the Riemann tensor.
In the case of a spacetime with axial symmetry, due to the conservation
property of Komar integrals, it is tempting to use this as the appropriate 
notion of total angular momentum at future null infinity. But in a 
realistic situation the spacetime will not have any symmetries and the 
problem remains.

We present here a new notion of intrinsic angular momentum at future null
infinity, based on the charge integrals approach, that is suitable for the 
general case of radiating spacetimes without symmetries, that do not 
suffer from supertranslations ambiguities, and in the case of axial 
symmetry it reduces to the Komar integral.