symmetric monoidal (∞,1)-category of spectra
Various phenomena in the context of algebraic geometry/arithmetic geometry (and particularly in the context of algebraic groups) over finite fields turn out to make perfect sense as expressions in when extrapolated to the case , and to reflect interesting (combinatorial, representation theoretical…) facts, even though, of course, there is no actual field with a single element (since in a field by definition the elements 1 and 0 are distinct).
Motivated by such observations, Jacques Tits envisioned in (Tits 57) a new kind of geometry adapted to the explanation of these identities. Christophe Soulé then expanded on Tits’ ideas by introducing the notion of field with one element and studying its fine arithmetic invariants. While there is no field with a single element in the standard sense of field, the idea is that there is some other object, denoted , such that it does make sense to speak of “geometry over ”. Following the French pronunciation one also writes (and is thus led to the inevitable pun).
In the relative point of view the -schemes are schemes with a morphism of schemes over a base scheme ; but every -scheme is a scheme over Spec(Z). In absolute algebraic geometry all “generalized schemes” should live over and should live below ; this is similar to the fact that the quotient stacks like live below the single point (there is a direct image functor from sheaves on a point to sheaves over ). One of the principal and very bold hopes is that the study of should lead to a natural proof of Riemann conjecture (see also MathOverflow here). It was originally suggested by (Manin 95) that the Riemann hypothesis might be solved by finding an -analogue of André Weil‘s proof for the case of arithmetic curves over the finite fields .
A first proposal for what a variety “over ” ought to be is due to (Soulé 04). After that a plethora of further proposals appeared, including (Connes-Consani 08).
Maybe an emerging consensus is that the preferred approach is Borger's absolute geometry (Borger 09). Here the structure of a Lambda-ring on a ring , hence on , is interpreted as a collection of lifts of all Frobenius morphisms and hence as descent data for descent to (which is defined thereby). This definition yields an essential geometric morphism of gros etale toposes
where on the right the notation is just suggestive, the topos is a suitable one over Lambda-rings. Here the middle inverse image is the forgetful functor which forgets the Lambda structure, and its right adjoint direct image is given by the arithmetic jet space construction (via the ring of Witt vectors construction).
This proposal seems to subsume many aspects of other existing proposals (see e.g. Le Bruyn 13) and stands out as yielding an “absolute base topos” which is rich and genuinely interesting in its own right.
One proposal here is to identify the concept of finite rank modules/finite-dimensional vector spaces over the field with one element with that of (pointed) finite sets
and hence the symmetric group on elements with the general linear group over :
(e.g. Cohn 04, “puzzle 1”, Durov 07, 2.5.6, Snyder 07)
But it has also been argued by Connes and Consani (see Beardsley & Nakamura 24, 2.3) that we should understand -modules as Segal -sets, i.e., pointed functors .
With the identification from above it follows that the algebraic K-theory over is stable cohomotopy:
Here in the second step we used the definition of algebraic K-theory for ordinary commutative rings as the K-theory of the permutative category of modules (this example), in the second step we used the identification of modules over with pointed finite sets from above, and finally we used the identification of the K-theory of the permutative category of finite set with the sphere spectrum (this example), which is the spectrum representing stable cohomotopy, by definition.
The perspective that the K-theory over should be stable Cohomotopy has been highlighted in (Deitmar 06, p. 2, Guillot 06, Mahanta 17, Dundas-Goodwillie-McCarthy 13, II 1.2, Morava, Connes-Consani 16).), and fully explicitly in Chu, Lorscheid & Santhanam 10, Thm. 5.9 and Beardsley & Nakamura 2024, Cor. 2.25. (Chu et al. also generalize to equivariant stable Cohomotopy and equivariant K-theory.)
With the understanding of -modules as -sets, remains equal to the sphere spectrum.
After the very first observations by Tits, pioneers were Christophe Soulé and Kapranov and Smirnov. More recently there are extensive works by Alain Connes and Katia Consani, Nikolai Durov, James Borger and Oliver Lorscheid.
Henry Cohn, Projective geometry over and the Gaussian binomial coefficients, American Mathematical Monthly 111 (2004), 487-495 (arXiv:math/0407093)
Lieven Le Bruyn, Looking for , blog
Javier López Peña, Oliver Lorscheid, Mapping -land:An overview of geometries over the field with one element, arXiv/0909.0069
Alain Connes, Fun with , 5 min. video
Lieven Le Bruyn, The field with one element, seminar notes 2008 (web)
Oliver Lorscheid, Lectures on , 2014 (pdf)
Oliver Lorscheid, for everyone, 2018 (arXiv:1801.05337)
Tim Hosgood, Under : a reader’s companion, master thesis, 2016 (pdf).
Jacques Tits, Sur les analogues algebriques des groupes semi-simples complexes. In Colloque d’algebre superieure, tenu a Bruxelles du 19 au 22 decembre 1956, Centre Belge de Recherches Mathematiques, pages 261-289. Etablissements Ceuterick, Louvain, 1957.
Christophe Soulé, Les varietes sur le corps a un element Mosc. Math. J., 4(1):217-244, 312, 2004 (pdf)
Yuri Manin, Lectures on zeta functions and motives (according to Deninger and Kurokawa) Asterisque, (228):4, 121-163, 1995. Columbia University Number Theory Seminar (pdf)
Bertrand Toen, Michel Vaquie, Under Spec Z (arXiv:math/0509684)
Around (0.4.24.2) in
the algebraic structure of is regarded as being the maybe monad, hence modules over are defined to be monad-algebras over the maybe monad, hence pointed sets.
Other approaches include
Alain Connes, Caterina Consani, Matilde Marcolli, Fun with , arxiv/0806.2401
Yuri Manin, Cyclotomy and analytic geometry over , arxiv/0809.1564
Alain Connes, Caterina Consani, On the notion of geometry over , arxiv/0809.2926;
Schemes over and zeta functions, arxiv/0903.2024; Characteristic one, entropy and the absolute point, in: Noncommutative Geometry, Arithmetic, and Related Topics, 21st Meeting of the Japan-U.S. Math. Inst., Baltimore 2009, JHUP (2012), pp. 75–139, arxiv/0911.3537;
From monoids to hyperstructures: in search of an absolute arithmetic, arxiv/1006.4810;
On the arithmetic of the BC-system, arxiv/1103.4672; Projective geometry in characteristic one and the epicyclic category, arxiv/1309.0406
M. Marcolli, Ryan Thorngren, Thermodynamical semirings, arXiv/1108.2874
Bora Yalkinoglu, On Endomotives, Lambda-rings and Bost-Connes systems, With an appendix by Sergey Neshveyev, arxiv/1105.5022
Jonathan Beardsley, So Nakamura, Projective Geometries and Simple Pointed Matroids as -modules [arXiv:2404.04730]
The approach in terms of Lambda-rings due to
with details in
James Borger, The basic geometry of Witt vectors, I: The affine case (arXiv:0801.1691)
James Borger, The basic geometry of Witt vectors, II: Spaces (arXiv:1006.0092)
More discussion relating to this includes
The interpretation of stable cohomotopy as algebraic K-theory over is amplified in the following articles:
Anton Deitmar, Remarks on zeta functions and K-theory over (arXiv:math/0605429)
Pierre Guillot, Adams operations in cohomotopy (arXiv:0612327)
Jack Morava, Rekha Santhanam, Power operations and absolute geometry, 2012 (pdf)
Snigdhayan Mahanta, G-theory of -algebras I: the equivariant Nishida problem, J. Homotopy Relat. Struct. 12 (4), 901-930, 2017 (arXiv:1110.6001)
John D. Berman, p. 92 of Categorified algebra and equivariant homotopy theory (arXiv:1805.08745)
Chenghao Chu, Oliver Lorscheid, Rekha Santhanam, Sheaves and K-theory for -schemes, Advances in Mathematics, Volume 229, Issue 4, 1 March 2012, Pages 2239-2286 (arxiv:1010.2896)
see also
Jack Morava, Some background on Manin’s theorem (pdf, MoravaSomeBackground.pdf)
Alain Connes, Caterina Consani, Absolute algebra and Segal’s Gamma sets, Journal of Number Theory 162 (2016): 518-551 (arXiv:1502.05585)
Speculation on quantum field theory over (via wonderful compactifications of configuration spaces of points)
Dori Bejleri, Matilde Marcolli, Quantum field theory over , Journal of Geometry and Physics 69 (2013) 40-59 [arXiv:1209.4837, doi:10.1016/j.geomphys.2013.03.002]
Seyed Khaki, Original in emergent spacetime [arXiv:2401.07822]
Last revised on April 9, 2024 at 11:11:47. See the history of this page for a list of all contributions to it.