2,746 research outputs found
Vigilant servant leadership
Over the last 70 years the Organic community has espoused a set of principles on which to farm, grow and live by. We have actively advocated the lifestyle, technologies and means to resolve many local and global issues which are now the titles of best-selling novels and treatise of recent times, Cradle to Cradle and Biomimicry to name a couple (Benyus 2002, McDonough & Braungart 2002). A carbon economy is exactly what we have espoused for decades. It is nice to feel we were right.
Continuing on a theme in the previous editorial, it is also very frustrating times. It is difficult to celebrate when generations of work is not acknowledged, or actively ignored. The symptoms of frustration abound; little or no research funding for Organic systems approaches is proportioned to our value to the food chain or calculated wider environment benefits and definitely less for the organisations that may organise it. While at the primary school level of education we have some success, we find there is diminishing support at the tertiary level. The situation is not better, it is worse. How could this be? How could we have permitted this to happen? Have we been absorbed, or peaked as a culture, accomplishing what we set out to do. I suggest not; the fun is just beginning, and so too the challenges
On integrable deformations of superstring sigma models related to AdS_n x S^n supercosets
We consider two integrable deformations of 2d sigma models on supercosets
associated with AdS_n x S^n. The first, the "eta-deformation" (based on the
Yang-Baxter sigma model), is a one-parameter generalization of the standard
superstring action on AdS_n x S^n, while the second, the "lambda-deformation"
(based on the deformed gauged WZW model), is a generalization of the
non-abelian T-dual of the AdS_n x S^n superstring. We show that the
eta-deformed model may be obtained from the lambda-deformed one by a special
scaling limit and analytic continuation in coordinates combined with a
particular identification of the parameters of the two models. The relation
between the couplings and deformation parameters is consistent with the
interpretation of the first model as a real quantum deformation and the second
as a root of unity quantum deformation. For the AdS_2 x S^2 case we then
explore the effect of this limit on the supergravity background associated to
the lambda-deformed model. We also suggest that the two models may form a dual
Poisson-Lie pair and provide direct evidence for this in the case of the
integrable deformations of the coset associated with S^2.Comment: v2: comments and references added; v3: new appendix on an alternative
proposal for the dilaton and minor changes, 28 pages; v4: misprint in (B.7)
correcte
Type IIB supergravity solution for the T-dual of the eta-deformed AdS_5 x S^5 superstring
We find an exact type IIB supergravity solution that represents a
one-parameter deformation of the T-dual of the AdS_5 x S^5 background (with
T-duality applied in all 6 abelian bosonic isometric directions). The
non-trivial fields are the metric, dilaton and RR 5-form only. The latter has
remarkably simple "undeformed" form when written in terms of a
"deformation-rotated" vielbein basis. An unusual feature of this solution is
that the dilaton contains a linear dependence on the isometric coordinates of
the metric precluding a straightforward reversal of T-duality. If we still
formally dualize back, we find exactly the metric, B-field and product of
dilaton with RR field strengths as recently extracted from the eta-deformed
AdS_5 x S^5 superstring action in arXiv:1507.04239. We also discuss similar
solutions for deformed AdS_n x S^n backgrounds with n=2,3. In the eta -> i
limit we demonstrate that all these backgrounds can be interpreted as special
limits of gauged WZW models and are also related to (a limit of) the
Pohlmeyer-reduced models of the AdS_n x S^n superstrings.Comment: 20 pages; v2: minor comments and clarifications added; v3: 21 pages,
minor comments and references adde
Type IIB supergravity solution for the T-dual of the eta-deformed AdS_5 x S^5 superstring
We find an exact type IIB supergravity solution that represents a
one-parameter deformation of the T-dual of the AdS_5 x S^5 background (with
T-duality applied in all 6 abelian bosonic isometric directions). The
non-trivial fields are the metric, dilaton and RR 5-form only. The latter has
remarkably simple "undeformed" form when written in terms of a
"deformation-rotated" vielbein basis. An unusual feature of this solution is
that the dilaton contains a linear dependence on the isometric coordinates of
the metric precluding a straightforward reversal of T-duality. If we still
formally dualize back, we find exactly the metric, B-field and product of
dilaton with RR field strengths as recently extracted from the eta-deformed
AdS_5 x S^5 superstring action in arXiv:1507.04239. We also discuss similar
solutions for deformed AdS_n x S^n backgrounds with n=2,3. In the eta -> i
limit we demonstrate that all these backgrounds can be interpreted as special
limits of gauged WZW models and are also related to (a limit of) the
Pohlmeyer-reduced models of the AdS_n x S^n superstrings.Comment: 20 pages; v2: minor comments and clarifications added; v3: 21 pages,
minor comments and references adde
Bound States of the q-Deformed AdS5 x S5 Superstring S-matrix
The investigation of the q deformation of the S-matrix for excitations on the
string world sheet in AdS5 x S5 is continued. We argue that due to the lack of
Lorentz invariance the situation is more subtle than in a relativistic theory
in that the nature of bound states depends on their momentum. At low enough
momentum |p|<E the bound states transform in the anti-symmetric representation
of the super-algebra symmetry and become the solitons of the Pohlmeyer reduced
theory in the relativistic limit. At a critical momentum |p|=E they become
marginally unstable, and at higher momenta the stable bound states are in the
symmetric representation and become the familiar magnons in the string limit as
q->1. This subtlety fixes a problem involving the consistency of crossing
symmetry with the relativistic limit found in earlier work. With mirror
kinematics, obtained after a double Wick rotation, the bound state structure is
simpler and there are no marginally unstable bound states.Comment: 25 page
Unifying Requirements and Code: an Example
Requirements and code, in conventional software engineering wisdom, belong to
entirely different worlds. Is it possible to unify these two worlds? A unified
framework could help make software easier to change and reuse. To explore the
feasibility of such an approach, the case study reported here takes a classic
example from the requirements engineering literature and describes it using a
programming language framework to express both domain and machine properties.
The paper describes the solution, discusses its benefits and limitations, and
assesses its scalability.Comment: 13 pages; 7 figures; to appear in Ershov Informatics Conference, PSI,
Kazan, Russia (LNCS), 201
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