The Royal Swedish Academy of Sciences said the two men had Â"placed particle physics theory on a firmer mathematical foundation.Â" It was the fifth time the physics prize had been awarded in the field of particle physics.
Â"They have in particular shown how the theory may be used for precise calculations of physical quantities,Â" results that have been confirmed in accelerator laboratories in Europe and the United States, the academy said.
Â"This is the entire framework we (particle physicists) use when calculating. We'll get finite answers. Earlier calculations only resulted in nonsense,Â" said Lars Brink, a professor of Chalmers Technical Institute and a member of the academy.
The Nobel Prize for chemistry was to be announced later Tuesday.
The academy's announcement said the work of 't Hooft and Veltman Â"has given researchers a well-functioning theoretical machinery which can be used for, among other things, predicting the properties of new particles.Â"
Their calculations were vital in calculating the mass of the top quark, which was observed for the first time in 1995 at the Fermilab in the United States.
Â"An important ingredient in the theory 't Hooft and Veltman have developed is an as yet undemonstrated particle termed the Higgs particle. In the same way as other particles have been predicted by theoretical arguments and later demonstrated experimentally, researchers are now awaiting direct observation of the Higgs particle,Â" the academy said.
Veltman, of Bilthoven, is retired from the University of Michigan, and 't Hooft has been a professor at the University of Utrecht since 1977. Their association began in 1969 when 't Hooft studied with Veltman.
The literature prize was awarded Thursday to German novelist Guenter Grass. The medicine prize was awarded Monday to Dr. Guenter Blobel, 63, a German native and U.S. citizen, who discovered how proteins find their rightful places in cells.
The economics prize winner is to be announced Wednesday in Stockholm and the peace prize on Friday in Oslo, Norway.
The prizes, worth $960,000, are presented on Dec. 10, the anniversary of the death of Alfred Nobel, the Swedish industrialist and inventor of dynamite who established the prizes.
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