36,784 research outputs found
Complete structure of Z_n Yukawa couplings
We give the complete twisted Yukawa couplings for all the Z_n orbifold
constructions in the most general case, i.e. when orbifold deformations are
considered. This includes a certain number of tasks. Namely, determination of
the allowed couplings, calculation of the explicit dependence of the Yukawa
couplings values on the moduli expectation values (i.e. the parameters
determining the size and shape of the compactified space), etc. The final
expressions are completely explicit, which allows a counting of the DIFFERENT
Yukawa couplings for each orbifold (with and without deformations). This
knowledge is crucial to determine the phenomenological viability of the
different schemes, since it is directly related to the fermion mass hierarchy.
Other facts concerning the phenomenological profile of Z_n orbifolds are also
discussed, e.g. the existence of non--diagonal entries in the fermion mass
matrices, which is related to a non--trivial structure of the
Kobayashi--Maskawa matrix. Finally some theoretical results are given, e.g. the
no--participation of (1,2) moduli in twisted Yukawa couplings. Likewise, (1,1)
moduli associated with fixed tori which are involved in the Yukawa coupling, do
not affect the value of the coupling.Comment: 60 page
Modified Renormalization Strategy for Sandpile Models
Following the Renormalization Group scheme recently developed by Pietronero
{\it et al}, we introduce a simplifying strategy for the renormalization of the
relaxation dynamics of sandpile models. In our scheme, five sub-cells at a
generic scale form the renormalized cell at the next larger scale. Now the
fixed point has a unique nonzero dynamical component that allows for a great
simplification in the computation of the critical exponent . The values
obtained are in good agreement with both numerical and theoretical results
previously reported.Comment: APS style, 9 pages and 3 figures. To be published in Phys. Rev.
Functional advantages offered by many-body coherences in biochemical systems
Quantum coherence phenomena driven by electronic-vibrational (vibronic)
interactions, are being reported in many pulse (e.g. laser) driven chemical and
biophysical systems. But what systems-level advantage(s) do such many-body
coherences offer to future technologies? We address this question for pulsed
systems of general size N, akin to the LHCII aggregates found in green plants.
We show that external pulses generate vibronic states containing particular
multipartite entanglements, and that such collective vibronic states increase
the excitonic transfer efficiency. The strength of these many-body coherences
and their robustness to decoherence, increase with aggregate size N and do not
require strong electronic-vibrational coupling. The implications for energy and
information transport are discussed.Comment: arXiv admin note: text overlap with arXiv:1706.0776
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