3,412 research outputs found
On the infrared limit of Horava's gravity with the global Hamiltonian constraint
We show that Horava's theory of gravitation with the global Hamiltonian
constraint does not reproduce General Relativity in the infrared domain. There
is one extra propagating degree of freedom, besides those two associated with
the massless graviton, which does not decouple.Comment: 7 pages, typos corrected, to be published in PR
Self-accelerating solutions in massive gravity on an isotropic reference metric
Within the framework of the recently proposed ghost-free massive gravity, a
cosmological constant-type self-accelerating solution has been obtained for
Minkowski and de Sitter reference metrics. We ease the assumption on the
reference metric and find the self-accelerating solution for the reference
metric respecting only isotropy, thus considerably extending the range of known
solutions.Comment: 4 pages; matches the published version in Phys. Rev.
Nonperturbative physics at short distances
There is accumulating evidence in lattice QCD that attempts to locate
confining fields in vacuum configurations bring results explicitly depending on
tha lattice spacing (that is, ultraviolet cut off). Generically, one deals with
low-dimensional vacuum defects which occupy a vanishing fraction of the total
four-dimensional space. We review briefly existing data on the vacuum defects
and their significance for confinement and other nonperturbative phenomena. We
introduce the notion of `quantum numbers' of the defects and draw an analogy,
rather formal one, to developments which took place about 50 years ago and were
triggered by creation of the Sakata model.Comment: 15 pages, contributed to International Symposium on the Jubilee of
the Sakata Model (pnLambda50), Nagoya, Japan, Nov. 200
From confining fields on the lattice to higher dimensions in the continuum
We discuss relation between lattice phenomenology of confining fields in the
vacuum state of Yang-Mills theories (mostly SU(2) case) and continuum theories.
In the continuum, understanding of the confinement is most straightforward in
the dual formulation which involves higher dimensions. We try to bridge these
two approaches to the confinement, let it be on a rudimentary level. We review
lattice data on low-dimensional defects, that is monopoles, center vortices,
topological defects. There is certain resemblance to dual strings, domain
walls, introduced in large-N Yang-Mills theories.Comment: 21 pages; based on three lectures given at the Conference ``Infrared
QCD in Rio'', Rio de Janeiro, Brazil, 5-0 June 200
Renormalons as a Bridge between Perturbative and Nonperturbative Physics
In two lectures, we overview the renormalon and renormalon-related techniques
and their phenomenological applications. We begin with a single renormalon
chain which is a well defined and systematic way to specify the character of
corrections in inverse powers of the total energy to observables directly in
Minkowski space. Renormalons demonstrate also presence of nonperturbative
contributions. We proceed then to multirenormalon chains and argue that they
are in fact not suppressed compared to a single chain. On one hand, this
phenomenon might be a mechanism for enhancement of power corrections. On the
other hand, the derivation of relations between power corrections to various
observables becomes a formidable task and asks for introduction of models. In
the concluding, third part we consider dynamical models for nonperturbative
effects, both in infrared and ultraviolet regions, inspired by renormalons.Comment: 31 pages, LaTeX file. Talk presented at YKIS97, Kyoto, December, 199
Dual string from lattice Yang-Mills theory
We review properties of lower-dimension vacuum defects observed in lattice
simulations of SU(2) Yang-Mills theories. One- and two-dimensional defects are
associated with ultraviolet divergent action. The action is the same divergent
as in perturbation theory but the fluctuations extend over submanifolds of the
whole 4d space. The action is self tuned to a divergent entropy and the 2d
defects can be thought of as dual strings populated with particles. The newly
emerging 3d defects are closely related to the confinement mechanism. Namely,
there is a kind of holography so that information on the confinement is encoded
in a 3d submanifold. We introduce an SU(2) invariant classification scheme
which allows for a unified description of d=1,2,3 defects. The scheme fits
known data and predicts that the 3d defects are related to chiral symmetry
breaking. Relation to stochastic vacuum model is briefly discussed as well.Comment: 11 pages,based on the talks presented at the conferences ``Quark
Confinement and the Hadron Spectrum VI'' (Village Tanka, September 2004) and
``QCD and String Theory'' (Santa Barbara, November 2004
- …