6,972 research outputs found
Wegner-Houghton equation in low dimensions
We consider scalar field theories in dimensions lower than four in the
context of the Wegner-Houghton renormalization group equations (WHRG). The
renormalized trajectory makes a non-perturbative interpolation between the
ultraviolet and the infrared scaling regimes. Strong indication is found that
in two dimensions and below the models with polynomial interaction are always
non-perturbative in the infrared scaling regime. Finally we check that these
results do not depend on the regularization and we develop a lattice version of
the WHRG in two dimensions.Comment: 44 pages, 9 figures; some sections revised, refs. added; final
version to appear in Phys. Rev.
Microscopic systems with and without Coulomb interaction, fragmentation and phase transitions in finite nuclei
We test the influence of the Coulomb interaction on the thermodynamic and
cluster generation properties of a system of classical particles described by
different lattice models. Numerical simulations show that the Coulomb
interaction produces essentially a shift in temperature of quantities like the
specific heat but not qualitative changes. We also consider a cellular model.
The thermodynamic properties of the system are qualitatively unaltered.Comment: 8 pages, 9 figures. New comments concerning the effect of the Coulomb
interaction on the caloric curve. Justification of the criterion which
defines bound clusters. Further comments about the identification of the
order of the transition. To be published in Eur. Phys. J.
Observers and their notion of spacetime beyond special relativity
It is plausible that quantum gravity effects may lead us to a description of
Nature beyond the framework of special relativity. In this case, either the
relativity principle is broken or it is maintained. These two scenarios (a
violation or a deformation of special relativity) are very different, both
conceptually and phenomenologically. We discuss some of their implications on
the description of events for different observers and the notion of spacetime.Comment: 10 page
Beyond Special Relativity at second order
The study of generic, non-linear, deformations of Special Relativity
parametrized by a high-energy scale , which was carried out at first order
in in Phys.Rev. D86, 084032 (2012), is extended to second order. This can
be done systematically through a ('generalized') change of variables from
momentum variables that transform linearly. We discuss the different
perspectives on the meaning of the change of variables, obtain the coefficients
of modified composition laws and Lorentz transformations at second order, and
work out how -Poincar\'e, the most commonly used example in the
literature, is reproduced as a particular case of the generic framework exposed
here.Comment: 19 page
Spacetime from locality of interactions in deformations of special relativity: the example of -Poincar\'e Hopf algebra
A new proposal for the notion of spacetime in a relativistic generalization
of special relativity based on a modification of the composition law of momenta
is presented. Locality of interactions is the principle which defines the
spacetime structure for a system of particles. The formulation based on
-Poincar\'e Hopf algebra is shown to be contained in this framework as
a particular example.Comment: 14 page
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