





I am working on a new book. If you are interested, the best place to start is with the following survey paper:
D. Joyce, 'An introduction to dmanifolds and derived differential geometry', pages 230281 in L. BrambilaPaz, O. GarciaPrada, P. Newstead and R.P. Thomas, editors, 'Moduli spaces', London Mathematical Society Lecture Note Series 411, Cambridge University Press, 2014.Here too is a "detailed summary" of the book, a longer survey paper, which basically corresponds to Chapter 1 and Appendix A of the current version of the book, and contains moreorless all the main definitions and theorems, but no proofs.
D. Joyce, 'Dmanifolds, dorbifolds and derived differential geometry: a detailed summary', arXiv:1208.4948, version 2, December 2012. 173 pages.
You can download a preliminary version of the book here:
'Dmanifolds and dorbifolds: a theory of derived differential geometry', pdf file. 768 pages.
You can also download the slides of a talk I gave on it in Luminy in July 2012 here:
'Dmanifolds and derived differential geometry'. pdf file
and the slides of three talks on 'Dmanifolds and dorbifolds: a theory of derived differential geometry', which I gave in Tokyo in July 2012:
Here is a survey paper on C^{∞}schemes and C^{∞}algebraic geometry which may be useful: arXiv:1104.4951.
When it's finished I'll try and persuade someone to publish it. This is work in progress. Please do send me comments about it, mistakes, etc.
Aside, added September 2014:I am planning to revise the dmanifolds book to redo the treatment
of dmanifolds and dorbifolds with corners, because the current
version of corners is not adequate for some applications I have in mind in
symplectic geometry. So publication is on hold for the moment.
I have also written a long paper arXiv:1409.6908 giving a new definition of Kuranishi space. This defines an ordinary category MKur of 'MKuranishi spaces' which is equivalent to the homotopy category Ho(dMan) of the strict 2category dMan of dmanifolds. It defines a weak 2category Kur of 'Kuranishi spaces', which is equivalent as a weak 2category to the strict 2category dOrb of dorbifolds. It also defines categories MKur^{b}, MKur^{c} of 'MKuranishi spaces with boundary' and 'with corners', and weak 2categories Kur^{b}, Kur^{c} of 'Kuranishi spaces with boundary' and 'with corners'. These are not equivalent to Ho(dMan^{b}), Ho(dMan^{c}), dOrb^{b}, dOrb^{c} for the definitions of dMan^{b}, dMan^{c}, dOrb^{b}, dOrb^{c} in the current version of the dmanifolds book, but they will be equivalent once I have revised it.
Thus, Kuranishi spaces, with my new definition, are essentially equivalent to dmanifolds and dorbifolds, and can be used instead for many purposes. Kuranishi spaces are more elementary, but dmanifolds and dorbifolds have some technical advantages  for instance, being embedded in larger 2categories of 'dspaces' and dstacks' which are closed under fibre products.Continuing original web page:
Here is a brief description of what the dmanifolds book is about. See the reference list at the end for relevant literature.
"Kuranishi spaces" are a class of geometric spaces introduced in 1990 by Fukaya and Ono, as the geometric structure on moduli spaces of Jholomorphic curves in a symplectic manifold, and used in the work of Fukaya, Oh, Ohta and Ono on Lagrangian Floer cohomology and Fukaya categories. Although their definition was sufficient for their applications, it did not give a very satisfactory notion of geometric space  notions of morphisms, or even of when two Kuranishi spaces are "the same", are not well behaved  so the theory of Kuranishi spaces was never developed very far. The book began as a project to find the "right" definition of Kuranishi space, which I believe I have done.
The book describes and studies a new class of geometric objects I call "dmanifolds". Dmanifolds are a kind of "derived" smooth manifold, where "derived" is in the sense of the derived algebraic geometry of Jacob Lurie, Bertrand Toen, etc. The closest thing to them in the literature is the "derived manifolds" of David Spivak. But dmanifolds are rather simpler than Spivak's derived manifolds  dmanifolds form a 2category which is constructed using fairly basic techniques from algebraic geometry, but derived manifolds form an ∞category (simplicial category) which uses advanced ideas like homotopy sheaves and Bousfeld localization.
Following Spivak, my dmanifolds are based on the idea of "C^{∞}schemes". These were invented in Synthetic Differential Geometry (see Dubuc, 1981, and my 2010 paper below), and are a way of applying the methods of Algebraic Geometry in the world of real smooth geometry to get a large class of geometric objects which include smooth manifolds, but also many singular spaces.
Manifolds are examples of dmanifolds  that is, the category of manifolds embeds as a subcategory of the 2category of dmanifolds  but dmanifolds also include many spaces one would regard classically as singular or obstructed. A dmanifold has a virtual dimension, an integer, which may be negative. Almost all the main ideas of differential geometry have analogues for dmanifolds  submersions, immersions, embeddings, submanifolds, orientations, transverse fibre products, and so on  but the derived versions are often stronger. For example, the intersection of two submanifolds in a manifold exists as a manifold if the intersection is transverse, but it always exists as a dmanifold. There are also good notions of dmanifolds with boundary and dmanifolds with corners, and orbifold versions of all this, dorbifolds. I claim that the (morally and aesthetically) "right" definition of Kuranishi space in the work of FukayaOhOhtaOno is that they are dorbifolds with corners.
A useful property of dmanifolds and dorbifolds is that they have wellbehaved virtual cycles or virtual chains. So, for example, if X is a compact oriented dmanifold of virtual dimension k, and Y is a manifold, and f : X →Y is a 1morphism, then we can define a virtual class [X] in the homology group H_{k}(Y; Z), which is unchanged under deformations of X,f. This will be important in applications of dmanifolds and dorbifolds.
Many important areas of mathematics involve "counting" moduli spaces of geometric objects to define enumerative invariants or homology theories  for instance, Donaldson and SeibergWitten invariants for 4manifolds, DonaldsonThomas invariants of CalabiYau 3folds, GromovWitten invariants in algebraic or symplectic geometry, instanton Floer cohomology, Lagrangian Floer cohomology, contact homology, Symplectic Field Theory, Fukaya categories, ... In all of these (at least over C for the algebraic geometry cases, and away from reducible connections, etc.) the moduli spaces concerned will be oriented dmanifolds or dorbifolds, and the counting can be done using virtual cycles or chains. So, dmanifolds and dorbifolds provide a unified way of looking at these counting problems. There are truncation functors from geometric structures currently used to define virtual classes to dmanifolds and dorbifolds. For instance, any moduli space of solutions of a smooth nonlinear elliptic p.d.e. on a compact manifold is a dmanifold. In algebraic geometry, a Cscheme with a perfect obstruction theory can be made into a dmanifold. In symplectic geometry, Kuranishi spaces and polyfold structures on moduli spaces of Jholomorphic curves induce dorbifold structures.
D. Borisov, 'Derived manifolds and Kuranishi models', arXiv:1212.1153.
D. Borisov and J. Noel, 'Simplicial approach to derived differential manifolds', arXiv:1112.0033.K. Fukaya, Y.G. Oh, H. Ohta and K. Ono, 'Lagrangian intersection Floer theory  anomaly and obstruction', Parts I and II. AMS/IP Studies in Advanced Mathematics, 46.1 and 46.2, A.M.S./International Press, 2009.
K. Fukaya and K. Ono, 'Arnold Conjecture and GromovWitten invariant', Topology 38 (1999), 9331048.
D. Joyce, 'Algebraic Geometry over C^{∞}rings', arXiv:1001.0023, 2010.
J. Lurie, 'Derived Algebraic Geometry I: Stable ∞categories', math.CT/0608228, 2006.
J. Lurie, 'Derived Algebraic Geometry V: Structured spaces', arXiv:0905.0459, 2009.
D.I. Spivak, 'Derived smooth manifolds', Duke Mathematical Journal 153 (2010), 55128. arXiv:0810.5174.