64,190 research outputs found
Instantons on hyperkähler manifolds
No full textAn instanton on a (pseudo-)hyperk\"ahler manifold is a vector bundle associated to a principal -bundle with a connection whose curvature is pointwise invariant under the quaternionic structures of , and thus satisfies the Yang-Mills equations. Revisiting a construction of solutions, we prove a local bijection between gauge equivalence classes of instantons on and equivalence classes of certain holomorphic functions taking values in the Lie algebra of defined on an appropriate -bundle over . Our reformulation affords a streamlined proof of Uhlenbeck's Compactness Theorem for instantons on (pseudo-)hyperk\"ahler manifolds
Hyperkähler cones and instantons on quaternionic Kähler manifolds
No full textWe present a novel approach to the study of Yang-Mills instantons on quaternionic Kähler manifolds, based on an extension of the harmonic space method of constructing instantons on hyperk\"ahler manifolds. Our results establish a bijection between local equivalence classes of instantons on quaternionic Kähler manifolds M and equivalence classes of certain holomorphic maps on an appropriate SL_2(C)-bundle over the Swann bundle of M
Hyperkähler cones and instantons on quaternionic Kähler manifolds
No full textWe present a novel approach to the study of Yang–Mills instantons on quaternionic Kähler manifolds, based on an extension of the harmonic space method of constructing instantons on hyperkähler manifolds. Our results establish a bijection between local equivalence classes of instantons on quaternionic Kähler manifolds M and equivalence classes of certain holomorphic maps on an appropriate SL 2(C) -bundle over the Swann bundle of M
Recent Progresses and Future Challenges in Developing the Concept of ‘Sustainable Forest Management’
No full textRecent developments in the implementation and enforcement of the EU Timber Regulation: signals of an emerging ‘due diligence jurisprudence’
No full textCompliance mechanisms of major global multilateral environmental agreements: hazardous materials
No full text
Hermitian surfaces and a twistor space of algebraic dimension
No full textWe study anti-self-dual hermitian surfaces with odd first Betti number. We show that the twistor space of a Hopf surface
M
M
has algebraic dimension 2, and we prove existence of half-conformally-flat metrics on the connected sum of copies of
M
M
and
C
P
2
\mathbb {C}{\mathbb {P}_2}
. Finally we emphasize some differences with the case
b
1
{b_1}
even.</p
BUILDING INTERSUBJECTIVITY AT A DISTANCE DURING THE COLLABORATIVE WRITING OF FAIRYTAILS.
No full textThis paper introduces intersubjectivity as a concept playing a crucial role in collaborative tasks, even when performed between partners at a distance. Two 5th grade classes from two European countries (Italy and Greece), collaborated in writing fairytales inspired by philosophically relevant issues. The software supporting the task is an asynchronous virtual environment. Videos recorded in the Italian class and materials posted on the platform were analyzed using qualitative approaches and discourse analysis. The case-study discussed shows how the construction of intersubjectivity at a distance is a complex process involving many aspects. The main results highlight how participants: (a) use the narrative structure as a pre-requisite to build an intersubjective space where partners representation plays an important role; (b) exploit to a high degree the intellectual reasoning needed to accomplish the task in a truly collaborative way; (b) attain a fine tuning of reflective and metacognitive skills fostering a genuine interdependency during the task. Within this process, computer mediation amplifies the partners ‘‘presence’’ all through the creative writing process, expanding [Bruner, J., 2002. Making stories: law, literature, life. Farrar Straus & Giroux] definition of writing as an activity where the ‘‘audience’’ plays a fundamental role as a ‘‘co-author’’
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