101,405 research outputs found
Beyond E11
We study the non-linear realisation of E11 originally proposed by West with
particular emphasis on the issue of linearised gauge invariance. Our analysis
shows even at low levels that the conjectured equations can only be invariant
under local gauge transformations if a certain section condition that has
appeared in a different context in the E11 literature is satisfied. This
section condition also generalises the one known from exceptional field theory.
Even with the section condition, the E11 duality equation for gravity is known
to miss the trace component of the spin connection. We propose an extended
scheme based on an infinite-dimensional Lie superalgebra, called the tensor
hierarchy algebra, that incorporates the section condition and resolves the
above issue. The tensor hierarchy algebra defines a generalised differential
complex, which provides a systematic description of gauge invariance and
Bianchi identities. It furthermore provides an E11 representation for the field
strengths, for which we define a twisted first order self-duality equation
underlying the dynamics.Comment: 97 pages. v2: Minor changes, references added. Published versio
On the extendedness of eigenstates in a hierarchical lattice: a critical view
We take a critical view at the basic definition of extended single particle
states in a non-translationally invariant system. For this, we present the case
of a hierarchical lattice and incorporate long range interactions that are also
distributed in a hierarchical fashion. We show that it is possible to
explicitly construct eigenstates with constant amplitudes (normalized to unity)
at every lattice point for special values of the electron- energy. However, the
end-to-end transmission, corresponding to the above energy of the electron in
such a hierarchical system depends strongly on a special correlation between
the numerical values of the parameters of the Hamiltonian. Keeping the energy
and the distribution of the amplitudes invariant, one can transform the lattice
from conducting to insulating simply by tunning the numerical values of the
long range interaction. The values of these interactions themselves display a
fractal character.Comment: 19 pages, 5 figure
Boolean Operations, Joins, and the Extended Low Hierarchy
We prove that the join of two sets may actually fall into a lower level of
the extended low hierarchy than either of the sets. In particular, there exist
sets that are not in the second level of the extended low hierarchy, EL_2, yet
their join is in EL_2. That is, in terms of extended lowness, the join operator
can lower complexity. Since in a strong intuitive sense the join does not lower
complexity, our result suggests that the extended low hierarchy is unnatural as
a complexity measure. We also study the closure properties of EL_ and prove
that EL_2 is not closed under certain Boolean operations. To this end, we
establish the first known (and optimal) EL_2 lower bounds for certain notions
generalizing Selman's P-selectivity, which may be regarded as an interesting
result in its own right.Comment: 12 page
Cooperativity Beyond Caging: Generalized Mode Coupling Theory
The validity of mode coupling theory (MCT) is restricted by an uncontrolled
factorization approximation of density correlations. The factorization can be
delayed and ultimately avoided, however, by explicitly including higher order
correlations. We explore this approach within a microscopically motivated
schematic model. Analytic tractability allows us to discuss in great detail the
impact of factorization at arbitrary order, including the limit of avoided
factorization. Our results indicate a coherent picture for the capabilities as
well as limitations of MCT. Moreover, including higher order correlations
systematically defers the transition and ultimately restores ergodicity.
Power-law divergence of the relaxation time is then replaced by continuous but
exponential growth.Comment: 4 pages, 2 figure
Solving the Hierarchy Problem without Supersymmetry or Extra Dimensions: An Alternative Approach
In this paper, we propose a possible new approach towards solving the gauge
hierarchy problem without supersymmetry and without extra spacetime dimensions.
This approach relies on the finiteness of string theory and the conjectured
stability of certain non-supersymmetric string vacua. One crucial ingredient in
this approach is the idea of ``misaligned supersymmetry'', which explains how
string theories may be finite even without exhibiting spacetime supersymmetry.
This approach towards solving the gauge hierarchy problem is therefore
complementary to recent proposals involving both large and small extra
spacetime dimensions. This approach may also give a new perspective towards
simultaneously solving the cosmological constant problem.Comment: 33 pages, LaTeX, 3 figure
Strange eigenstates and anomalous transport in a Koch fractal with hierarchical interaction
Stationary states of non-interacting electrons on a Koch fractal are
investigated within a tight binding approach. It is observed that if a
hierarchically long range hopping is allowed, a suitable correlation between
the parameters defining the Hamiltonian leads to spectacular changes in the
transport properties of finite, but arbitrarily large fractals. Topologically
identical structures, that are found to support the same distribution of the
amplitudes of eigenstates, are conducting in some cases and insulating in the
others, depending on the choice of the hierarchy parameter. The values of the
hierarchical parameter themselves display a self-similar, fractal character.Comment: 6 pages, 5 figure
Gardner's deformations as generators of new integrable systems
We re-address the problem of construction of new infinite-dimensional
completely integrable systems on the basis of known ones, and we reveal a
working mechanism for such transitions. By splitting the problem's solution in
two steps, we explain how the classical technique of Gardner's deformations
facilitates -- in a regular way -- making the first, nontrivial move, in the
course of which the drafts of new systems are created (often, of hydrodynamic
type). The other step then amounts to higher differential order extensions of
symbols in the intermediate hierarchies (e.g., by using the techniques of
Dubrovin et al. [1,2] and Ferapontov et al. [3,4]).Comment: Accepted to Proc. Int. workshop 'Physics and Mathematics of Nonlinear
Phenomena' (June 22-29, 2013; Gallipoli (LE), Italy), 6 page
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