Editing Tropical geometry

{{short description|Skeletonized version of algebraic geometry}}
{{Use dmy dates|date=June 2024}}
[[File:Cubique tropicale min.svg|thumbnail|A tropical cubic curve]]
In [[mathematics]], '''tropical geometry''' is the study of [[polynomial]]s and their [[algebraic geometry|geometric properties]] when addition is replaced with minimization and multiplication is replaced with ordinary addition:

: <math>x\oplus y=\min\{x,y\}</math>,
: <math>x\otimes y=x+y</math>.

So for example, the classical polynomial <math>x^3+xy+y^4</math> would become <math>\min\{x+x+x,\;x+y,\;y+y+y+y\}</math>. Such polynomials and their solutions have important applications in optimization problems, for example the problem of optimizing departure times for a network of trains.

Tropical geometry is a variant of [[algebraic geometry]] in which polynomial graphs resemble [[piecewise linear manifold|piecewise linear]] meshes, and in which numbers belong to the [[tropical semiring]] instead of a field. Because classical and tropical geometry are closely related, results and methods can be converted between them. Algebraic varieties can be mapped to a tropical counterpart and, since this process still retains some geometric information about the original variety, it can be used to help prove and generalize classical results from algebraic geometry, such as the [[Brill–Noether theorem]] or computing [[Gromov–Witten invariants]], using the tools of tropical geometry.<ref>{{Cite web|url=https://www.quantamagazine.org/tinkertoy-models-produce-new-geometric-insights-20180905/|title=Tinkertoy Models Produce New Geometric Insights|last=Hartnett|first=Kevin|website=[[Quanta Magazine]]|date=5 September 2018 |access-date=12 December 2018}}</ref>
<!---
It a relatively new area in [[mathematics]], which might loosely be described as a [[piecewise linear manifold|piecewise linear]] or skeletonized version of [[algebraic geometry]], using the [[tropical semiring]] instead of a field.!--->

== History ==
The basic ideas of tropical analysis were developed independently using the same notation by mathematicians working in various fields.<ref>See {{Cite book|last=Cuninghame-Green|first=Raymond A.| year=1979|title=Minimax algebra|series=Lecture Notes in Economics and Mathematical Sciences|volume=166|publisher=Springer |isbn=978-3-540-09113-4 |postscript=none }} and references therein.</ref> The central ideas of tropical geometry appeared in different forms in a number of earlier works. For example, [[Victor Pavlovich Maslov]] introduced a tropical version of the process of integration. He also noticed that the [[Legendre transformation]] and solutions of the [[Hamilton–Jacobi equation]] are linear operations in the tropical sense.<ref>{{Cite journal|last=Maslov|first=Victor|author-link=Victor Pavlovich Maslov|year=1987|title=On a new superposition principle for optimization problems|journal=[[Russian Mathematical Surveys]]|volume=42|issue=3|pages=43–54|bibcode=1987RuMaS..42...43M|doi=10.1070/RM1987v042n03ABEH001439|s2cid=250889913 }}</ref> However, only since the late 1990s has an effort been made to consolidate the basic definitions of the theory. This was motivated by its application to [[enumerative geometry|enumerative algebraic geometry]], with ideas from [[Maxim Kontsevich]]<ref>{{cite arXiv|last1=Kontsevich|first1=Maxim|author-link=Maxim Kontsevich|last2=Soibelman|first2=Yan|date=7 November 2000|title=Homological mirror symmetry and torus fibrations|eprint=math/0011041}}</ref> and works by Grigory Mikhalkin<ref>{{cite journal|last=Mikhalkin|first=Grigory|date=2005|title=Enumerative tropical algebraic geometry in R<sup>2</sup> |url=http://www.ams.org/journals/jams/2005-18-02/S0894-0347-05-00477-7/S0894-0347-05-00477-7.pdf |journal=[[Journal of the American Mathematical Society]] |volume=18 |issue=2 |pages=313–377|arxiv=math/0312530|doi=10.1090/S0894-0347-05-00477-7}}</ref> among others.

The adjective ''[[tropical]]'' was coined by French mathematicians in honor of the [[Hungary|Hungarian]]-born [[Brazil]]ian computer scientist [[Imre Simon]], who wrote on the field. [[Jean-Éric Pin]] attributes the coinage to [[Dominique Perrin]],<ref name="Pin1998">{{cite book |last=Pin |first=Jean-Eric |chapter=Tropical semirings |editor-last=Gunawardena |editor-first=J. |title=Idempotency |chapter-url=https://hal.archives-ouvertes.fr/hal-00113779/file/Tropical.pdf |publisher=[[Cambridge University Press]] |series=Publications of the Newton Institute |volume=11 |year=1998 |pages=50–69 |doi=10.1017/CBO9780511662508.004 |isbn=9780511662508}}</ref> whereas Simon himself attributes the word to Christian Choffrut.<ref name="Simon1988">{{Cite book |doi = 10.1007/BFb0017135 |volume = 324 |pages = 107–120 |series = [[Lecture Notes in Computer Science]] |year = 1988 |last1 = Simon |first1 = Imre |title = Mathematical Foundations of Computer Science 1988 |chapter = Recognizable sets with multiplicities in the tropical semiring |publisher = Springer |location = Berlin/Heidelberg |isbn = 978-3-540-50110-7}}</ref>

== Algebra background ==
{{further|Tropical semiring}}

Tropical geometry is based on the [[tropical semiring]]. This is defined in two ways, depending on max or min convention.

The ''min tropical semiring'' <math>\mathbb{T}</math> is the [[semiring]] <math>\mathbb{T}=(\R\cup\{+\infty\},\oplus,\otimes)</math>, with the operations:
: <math>x\oplus y=\min\{x,y\}</math>,
: <math>x\otimes y=x+y</math>.
The operations <math>\oplus</math> and <math>\otimes</math> are referred to as ''tropical addition'' and ''tropical multiplication'' respectively. The [[identity element]] for <math>\oplus</math> is <math>+\infty</math>, and the identity element for <math>\otimes</math> is 0.

Similarly, the ''max tropical semiring'' <math>\mathbb{T}</math> is the semiring <math>\mathbb{T}=(\R\cup\{-\infty\},\oplus,\otimes) </math>, with operations:

: <math>x\oplus y=\max\{x,y\}</math>,
: <math>x\otimes y=x+y</math>.

The identity element for <math>\oplus</math> is <math>-\infty</math>, and the identity element for <math>\otimes</math> is 0.

These semirings are isomorphic, under negation <math>x \mapsto -x</math>, and generally one of these is chosen and referred to simply as the ''tropical semiring''. Conventions differ between authors and subfields: some use the ''min'' convention, some use the ''max'' convention.

The tropical semiring operations model how [[valuation (algebra)|valuations]] behave under addition and multiplication in a [[valued field]].

Some common valued fields encountered in tropical geometry (with min convention) are:

* <math>\Q</math> or <math>\Complex</math> with the trivial valuation, <math>v(a)=0</math> for all <math>a\ne0</math>.
* <math>\Q</math> or its extensions with the [[p-adic valuation]], <math>v_p(p^n a/b)=n</math> for ''a'' and ''b'' coprime to ''p''.
* The field of [[Laurent series]] <math>\Complex(\!(t)\!)</math> (integer powers), or the field of (complex) [[Puiseux series]] <math>\Complex\{\!\{t\}\!\}</math>, with valuation returning the smallest exponent of ''t'' appearing in the series.

== Tropical polynomials ==
A ''tropical polynomial'' is a function <math>F:\R^n\to\R</math> that can be expressed as the tropical sum of a finite number of [[Monomial|''monomial terms'']]. A monomial term is a tropical product (and/or quotient) of a constant and variables from <math>X_1,\ldots,X_n</math>. Thus a tropical polynomial <math>F</math> is the minimum of a finite collection of [[Affine transformation|affine-linear functions]] in which the variables have integer coefficients, so it is [[concave function|concave]], [[continuous function|continuous]], and [[piecewise linear function|piecewise linear]].<ref name=SpeyerSturmfels2009>{{citation|first1=David|last1=Speyer |first2=Bernd|last2=Sturmfels|author2-link= Bernd Sturmfels |title=Tropical mathematics|journal=Mathematics Magazine|volume=82|issue=3|year=2009|pages=163–173|url=https://math.berkeley.edu/~bernd/mathmag.pdf|doi=10.1080/0025570X.2009.11953615 |s2cid=15278805 }}</ref>
:<math>
 \begin{align}F(X_1,\ldots,X_n)&=\left(C_1\otimes X_1^{\otimes a_{11}}\otimes\cdots\otimes X_n^{\otimes a_{n1}}\right)\oplus\cdots\oplus\left(C_s\otimes X_1^{\otimes a_{1s}}\otimes\cdots\otimes X_n^{\otimes a_{ns}}\right)\\&=\min\{C_1+a_{11}X_1+\cdots+a_{n1}X_n,\;\ldots,\;C_s+a_{1s}X_1+\cdots+a_{ns}X_n\}\end{align}
</math>

Given a polynomial <math>f</math> in the [[Laurent polynomial|Laurent polynomial ring]] <math>K[x_1^{\pm 1},\ldots,x_n^{\pm1}]</math> where <math>K</math> is a valued field, the ''tropicalization'' of <math>f</math>, denoted <math>\operatorname{Trop}(f)</math>, is the tropical polynomial obtained from <math>f</math> by replacing multiplication and addition by their tropical counterparts and each constant in <math>K</math> by its valuation. That is, if 
:<math> f=\sum_{i=1}^s c_i x^{A_i}\quad \text{with }A_1,\ldots,A_s\in\Z^n</math>,
then
:<math>\operatorname{Trop}(f)=\bigoplus_{i=1}^s v(c_i)\otimes X^{\otimes A_i} </math>.

The set of points where a tropical polynomial <math>F</math> is non-differentiable is called its associated ''tropical hypersurface'', denoted <math>\mathrm{V}(F)</math> (in analogy to the [[Algebraic variety|vanishing set]] of a polynomial). Equivalently, <math>\mathrm{V}(F)</math> is the set of points where the minimum among the terms of <math>F</math> is achieved at least twice. When <math>F=\operatorname{Trop}(f)</math> for a Laurent polynomial <math>f</math>, this latter characterization of <math>\mathrm{V}(F)</math> reflects the fact that at any solution to <math>f=0</math>, the minimum valuation of the terms of <math>f</math> must be achieved at least twice in order for them all to cancel.<ref name=Maclagan>{{cite book|last1=Maclagan|first1=Diane|author-link=Diane Maclagan|last2=Sturmfels|first2=Bernd |author2-link=Bernd Sturmfels|title= Introduction to Tropical Geometry |title-link= Introduction to Tropical Geometry |year=2015|publisher=[[American Mathematical Society]]|isbn=9780821851982 }}</ref>

== Tropical varieties ==
=== Definitions ===
For ''X'' an [[algebraic variety]] in the [[algebraic torus]] <math>(K^{\times})^n</math>, the ''tropical variety'' of ''X'' or ''tropicalization'' of ''X'', denoted <math>\operatorname{Trop}(X)</math>, is a subset of <math>\R^n</math> that can be defined in several ways. The equivalence of these definitions is referred to as the ''Fundamental Theorem of Tropical Geometry''.<ref name=Maclagan />

==== Intersection of tropical hypersurfaces ====
Let <math>\mathrm{I}(X)</math> be the ideal of Laurent polynomials that vanish on ''X'' in <math>K[x_1^{\pm 1},\ldots,x_n^{\pm1}]</math>. Define
:<math>\operatorname{Trop}(X)=\bigcap_{f\in\mathrm{I}(X)}\mathrm{V}(\operatorname{Trop}(f))\subseteq\R^n </math>
When ''X'' is a hypersurface, its vanishing ideal <math>\mathrm{I}(X)</math> is a [[principal ideal]] generated by a Laurent polynomial ''f'', and the tropical variety <math>\operatorname{Trop}(X)</math> is precisely the tropical hypersurface <math>\mathrm{V}(\operatorname{Trop}(f))</math>.

Every tropical variety is the intersection of a finite number of tropical hypersurfaces. A finite set of polynomials <math>\{f_1,\ldots,f_r\}\subseteq\mathrm{I}(X)</math> is called a ''tropical basis'' for ''X'' if <math>\operatorname{Trop}(X)</math> is the intersection of the tropical hypersurfaces of <math>\operatorname{Trop}(f_1),\ldots,\operatorname{Trop}(f_r)</math>. In general, a generating set of <math>\mathrm{I}(X)</math> is not sufficient to form a tropical basis. The intersection of a finite number of a tropical hypersurfaces is called a ''tropical prevariety'' and in general is not a tropical variety.<ref name=Maclagan />

==== Initial ideals ====
Choosing a vector <math>\mathbf{w}</math> in <math>\R^n</math> defines a map from the monomial terms of <math>K[x_1^{\pm 1},\ldots,x_n^{\pm1}]</math> to <math>\R</math> by sending the term ''m'' to <math>\operatorname{Trop}(m)(\mathbf{w})</math>. For a Laurent polynomial <math>f=m_1+\cdots+m_s</math>, define the ''initial form'' of ''f'' to be the sum of the terms <math>m_i</math> of ''f'' for which <math>\operatorname{Trop}(m_i)(\mathbf{w})</math> is minimal. For the ideal <math>\mathrm{I}(X)</math>, define its ''initial ideal'' with respect to <math>\mathbf{w}</math> to be
:<math>\operatorname{in}_{\mathbf{w}}\mathrm{I}(X)=(\operatorname{in}_{\mathbf{w}}(f):f\in\mathrm{I}(X))</math>.
Then define
:<math>\operatorname{Trop}(X) =\{\mathbf{w}\in\R^n:\operatorname{in}_{\mathbf{w}}\mathrm{I}(X)\neq(1)\} </math>.
Since we are working in the Laurent ring, this is the same as the set of weight vectors for which <math>\operatorname{in}_{\mathbf{w}}\mathrm{I}(X)</math> does not contain a monomial.

When ''K'' has trivial valuation, <math>\operatorname{in}_{\mathbf{w}}\mathrm{I}(X)</math> is precisely the initial ideal of <math>\mathrm{I}(X)</math> with respect to the [[Monomial order#Weight order|monomial order]] given by a weight vector <math>\mathbf{w}</math>. It follows that <math>\operatorname{Trop}(X)</math> is a subfan of the [[Gröbner fan]] of <math>\mathrm{I}(X)</math>.

==== Image of the valuation map ====
Suppose that ''X'' is a variety over a field ''K'' with valuation ''v'' whose image is dense in <math>\R</math> (for example a field of Puiseux series). By acting coordinate-wise, ''v'' defines a map from the algebraic torus <math>(K^{\times})^n</math> to <math>\R^n</math>. Then define
:<math>\operatorname{Trop}(X)=\overline{\{(v(x_1),\ldots,v(x_n)):(x_1,\ldots,x_n)\in X\}} </math>,
where the overline indicates the [[Closure (mathematics)|closure]] in the [[Euclidean topology]]. If the valuation of ''K'' is not dense in <math>\R</math>, then the above definition can be adapted by [[Change of rings#Extension of scalars|extending scalars]] to larger field which does have a dense valuation.

This definition shows that <math>\operatorname{Trop}(X)</math> is the non-Archimedean [[Amoeba (mathematics)|amoeba]] over an [[algebraically closed field|algebraically closed]] [[non-Archimedean field]] ''K''.<ref>{{cite book | last=Mikhalkin | first=Grigory | chapter=Amoebas of algebraic varieties and tropical geometry | editor1-last=Donaldson | editor1-first=Simon | editor1-link=Simon Donaldson | editor2-first=Yakov | editor2-last=Eliashberg | editor2-link=Yakov Eliashberg | editor3-first=Mikhael | editor3-last=Gromov | editor3-link=Mikhail Leonidovich Gromov | title=Different faces of geometry | location=New York, NY | publisher=Kluwer Academic/Plenum Publishers | series=International Mathematical Series | volume=3 | pages=257–300 | year=2004 | isbn=978-0-306-48657-9 | zbl=1072.14013 }}</ref>

If ''X'' is a variety over <math>\Complex</math>, <math>\operatorname{Trop}(X)</math> can be considered as the limiting object of the amoeba <math>\operatorname{Log}_t(X)</math> as the base ''t'' of the logarithm map goes to infinity.<ref>{{citation | first=Eric | last=Katz |author-link=Eric Katz| title=What is Tropical Geometry? | journal=[[Notices of the American Mathematical Society]] | volume=64 | issue=4 | pages=380–382 | url=https://www.ams.org/publications/journals/notices/201704/rnoti-p380.pdf |doi=10.1090/noti1507| year=2017 | doi-access=free }}</ref>

==== Polyhedral complex ====
The following characterization describes tropical varieties intrinsically without reference to algebraic varieties and tropicalization. A set ''V'' in <math>\R^n</math> is an irreducible tropical variety if it is the support of a weighted [[polyhedral complex]] of pure dimension ''d'' that satisfies the ''zero-tension condition'' and is connected in codimension one. When ''d'' is one, the zero-tension condition means that around each vertex, the weighted-sum of the out-going directions of edges equals zero. For higher dimension, sums are taken instead around each cell of dimension <math>d-1</math> after quotienting out the affine span of the cell.<ref name=SpeyerSturmfels2009/> The property that ''V'' is connected in codimension one means for any two points lying on dimension ''d'' cells, there is a path connecting them that does not pass through any cells of dimension less than <math>d-1</math>.<ref>{{citation| first1=Dustin | last1=Cartwright | first2=Sam | last2=Payne | title=Connectivity of tropicalizations | journal=Mathematical Research Letters | volume=19 | issue=5 | year=2012 | pages=1089–1095 | doi=10.4310/MRL.2012.v19.n5.a10 | arxiv=1204.6589 | bibcode=2012arXiv1204.6589C | s2cid=51767353 }}</ref>

=== Tropical curves ===
The study of ''tropical curves'' (tropical varieties of dimension one) is particularly well developed and is strongly related to [[graph theory]]. For instance, the theory of [[Divisor (algebraic geometry)|divisors]] of tropical curves are related to [[chip-firing game]]s on graphs associated to the tropical curves.<ref>{{Cite journal|date=1 September 2013|title=Rank of divisors on tropical curves|journal=[[Journal of Combinatorial Theory|Journal of Combinatorial Theory, Series A]]| language=en|volume=120|issue=7|pages=1521–1538|doi=10.1016/j.jcta.2013.05.002|issn=0097-3165|last1=Hladký|first1=Jan|last2=Králʼ|first2=Daniel|last3=Norine|first3=Serguei|arxiv=0709.4485|s2cid=3045053}}</ref>

Many classical theorems of algebraic geometry have counterparts in tropical geometry, including:

* [[Pappus's hexagon theorem]].<ref>{{Cite journal|last=Tabera|first=Luis Felipe|date=1 January 2005|title=Tropical constructive Pappus' theorem|journal=[[International Mathematics Research Notices]]| language=en|volume=2005|issue=39|pages=2373–2389|doi=10.1155/IMRN.2005.2373|issn=1073-7928|arxiv=math/0409126|doi-access=<!-- Not free-->|s2cid=14250249 }}</ref>  
* [[Bézout's theorem]]. 
* The [[degree-genus formula]].
* The [[Riemann–Roch theorem]].<ref>{{Cite journal|last1=Kerber|first1=Michael|last2=Gathmann|first2=Andreas|date=1 May 2008|title=A Riemann–Roch theorem in tropical geometry|journal=[[Mathematische Zeitschrift]]| language=en|volume=259|issue=1|pages=217–230|doi=10.1007/s00209-007-0222-4|issn=1432-1823|arxiv=math/0612129|s2cid=15239772}}</ref>
* The [[elliptic curve|group law of the cubics]].<ref>{{cite book | last1=Chan | first1=Melody | author1-link = Melody Chan | last2=Sturmfels | first2=Bernd | author2-link=Bernd Sturmfels | chapter=Elliptic curves in honeycomb form | zbl=1312.14142 | editor1-last=Brugallé | editor1-first=Erwan | title=Algebraic and combinatorial aspects of tropical geometry. Proceedings based on the CIEM workshop on tropical geometry, International Centre for Mathematical Meetings (CIEM), Castro Urdiales, Spain, December 12–16, 2011 | location=Providence, RI | publisher=[[American Mathematical Society]] | isbn=978-0-8218-9146-9 | series=Contemporary Mathematics | volume=589 | pages=87–107 | year=2013 | arxiv=1203.2356 | bibcode=2012arXiv1203.2356C }}</ref>

[[Oleg Viro]] used tropical curves to classify real curves of degree 7 in the plane up to [[Homotopy#Isotopy|isotopy]]. His method of ''patchworking'' gives a procedure to build a real curve of a given isotopy class from its tropical curve.

== Applications ==
A tropical line appeared in [[Paul Klemperer]]'s design of [[auction]]s used by the [[Bank of England]] during the financial crisis in 2007.<ref>{{Cite web|url = https://www.economics.ox.ac.uk/news/how-geometry-came-to-the-rescue-during-th |title = How geometry came to the rescue during the banking crisis|access-date = 24 March 2014|website = Department of Economics, University of Oxford}}</ref> Yoshinori Shiozawa defined subtropical algebra as max-times or min-times semiring (instead of max-plus and min-plus). He found that Ricardian trade theory (international trade without input trade) can be interpreted as a subtropical convex algebra.<ref>{{Cite journal |doi = 10.1007/s40844-015-0012-3|title = International trade theory and exotic algebras |url=https://www.researchgate.net/publication/280646264 |journal = Evolutionary and Institutional Economics Review|volume = 12|pages = 177–212|year = 2015|last1 = Shiozawa|first1 = Yoshinori|issue = 1 |s2cid = 155827635 }} This is a digest of Y. Shiozawa, "[https://www.researchgate.net/publication/236020268 Subtropical Convex Geometry as the Ricardian Theory of International Trade]" draft paper.</ref>{{primary source inline|date=September 2024}} Tropical geometry has also been used for analyzing neural networks. One such result is that feedforward neural networks with [[Rectifier (neural networks)|ReLU activation]] are exactly tropical rational curves.<ref>{{cite conference|last1=Zhang|first1=Liwen|author-link1=|last2=Naitzat|first2=Gregory|author-link2=|last3=Lim|first3=Lek-Heng|author3-link=Lek-Heng Lim|date=2018|title=Tropical Geometry of Deep Neural Networks|url=http://proceedings.mlr.press/v80/zhang18i.html|conference=35th International Conference on Machine Learning|location=|publisher=|pages=5824–5832|id=|book-title=Proceedings of the 35th International Conference on Machine Learning}}</ref>
 
Moreover, several optimization problems arising for instance in job scheduling, location analysis, transportation networks, decision making and discrete event dynamical systems can be formulated and solved in the framework of tropical geometry.<ref>{{cite book |last= Krivulin |first= Nikolai |arxiv=1408.0313 |chapter= Tropical optimization problems |year=2014 |title=Advances in Economics and Optimization: Collected Scientific Studies Dedicated to the Memory of L. V. Kantorovich |pages=195–214 |publisher=Nova Science Publishers |location=New York |isbn=978-1-63117-073-7 |editor1=Leon A. Petrosyan |editor2=David W. K. Yeung |editor3=Joseph V. Romanovsky}}</ref> A tropical counterpart of the [[Abel–Jacobi map]] can be applied to a crystal design.<ref>{{cite book |author-link=Toshikazu Sunada|last=Sunada |first=T. |year=2012 |title=Topological Crystallography: With a View Towards Discrete Geometric Analysis |series=Surveys and Tutorials in the Applied Mathematical Sciences |volume=6 |publisher=Springer Japan |isbn=9784431541769}}</ref> The weights in a [[weighted finite-state transducer]] are often required to be a tropical semiring. Tropical geometry can show [[self-organized criticality]].<ref>{{Cite journal|last1=Kalinin|first1=N.|last2=Guzmán-Sáenz|first2=A.|last3=Prieto|first3=Y.|last4=Shkolnikov|first4=M.|last5=Kalinina|first5=V.|last6=Lupercio|first6=E.|date=15 August 2018|title=Self-organized criticality and pattern emergence through the lens of tropical geometry|journal=[[Proceedings of the National Academy of Sciences of the United States of America]]| volume=115|issue=35|language=en|pages=E8135–E8142|doi=10.1073/pnas.1805847115|issn=0027-8424|pmid=30111541|pmc=6126730|arxiv=1806.09153|bibcode=2018PNAS..115E8135K|doi-access=free}}</ref>

Tropical geometry has also found applications in several topics within theoretical high energy physics. In particular, tropical geometry has been used to drastically simplify string theory amplitudes to their field-theoretical limits <ref>{{cite journal| last = Tourkine| first = Piotr| title = Tropical Amplitudes| journal = Annales Henri Poincaré| volume = 18| issue = 6| pages = 2199–2249| date = 2017| doi = 10.1007/s00023-017-0560-7| arxiv = 1309.3551| bibcode = 2017AnHP...18.2199T}}</ref> and has found connections to constructions such as the [[Amplituhedron]]<ref>{{cite journal| last1 = Arkani-Hamed| first1 = Nima| last2 = Trnka| first2 =  Jaroslav| title = The Amplituhedron| journal = JHEP| volume = 2014| pages = 030| date = 2014| issue = 10| doi = 10.1007/JHEP10(2014)030| arxiv = 1312.2007| bibcode = 2014JHEP...10..030A}}</ref> and tropological (topological Carrollian) sigma models.<ref>{{cite journal| last1 = Albrychiewicz| first1 = Emil| last2 = Ellers| first2 = Kai-Isaak| last3 = Franco Valiente| first3 = Andrés| last4 = Hořava| first4 = Petr| title = Tropological sigma models| journal = JHEP| volume = 06| pages = 135| date = 2024| issue = 6| doi = 10.1007/JHEP06(2024)135| arxiv = 2311.00745| bibcode = 2024JHEP...06..135A}}</ref>

==See also==
* [[Tropical analysis]]
* [[Tropical compactification]]

==Notes==
{{reflist}}

==References==
{{Refbegin}}
* [[Victor Pavlovich Maslov|Maslov, Victor]] (1986). "New superposition principle for optimization problems", Séminaire sur les Équations aux Dérivées Partielles 1985/6, Centre de Mathématiques de l’École Polytechnique, Palaiseau, exposé 24.
* Maslov, Victor (1987). "Méthodes Opératorielles".  Moscou, Mir, 707 p. (See Chapter 8, Théorie linéaire sur semi moduli, pp.&nbsp;652–701).
*{{cite journal |last1=Bogart |first1=Tristram |last2=Jensen |first2=Anders |last3=Speyer |first3=David |last4=Sturmfels |first4=Bernd | author4-link=Bernd Sturmfels | last5=Thomas |first5=Rekha |arxiv=math/0507563 |title=Computing Tropical Varieties |year=2005 |doi=10.1016/j.jsc.2006.02.004 |volume=42 |issue=1–2 |journal=Journal of Symbolic Computation |pages=54–73|bibcode=2005math......7563B |s2cid=24788157 }}
*{{cite journal |last1=Einsiedler |first1=Manfred |last2=Kapranov |first2=Mikhail |last3=Lind |first3=Douglas |arxiv=math/0408311 |title=Non-archimedean amoebas and tropical varieties |journal=J. Reine Angew. Math. |volume=601 |pages=139–157 |year=2006  |bibcode=2004math......8311E }}
*{{cite arXiv |last= Gathmann |first= Andreas |eprint=math/0601322v1 |title=Tropical algebraic geometry |year= 2006 }}
*{{cite book|last=Gross|first=Mark|title=Tropical geometry and mirror symmetry|year=2010|publisher=Published for the Conference Board of the Mathematical Sciences by the American Mathematical Society with support from the National Science Foundation|location=Providence, R.I.|isbn=9780821852323}}
*{{cite book|last=Itenberg|first=Illia|author2=Grigory Mikhalkin |author3=Eugenii Shustin  |title=Tropical algebraic geometry|year=2009|publisher=Birkhäuser Basel|location=Basel|isbn=9783034600484|edition=2nd | zbl=1165.14002 }}
*{{cite book|last1=Maclagan|first1=Diane|last2=Sturmfels|first2=Bernd |title=Introduction to tropical geometry|year=2015|publisher=American Mathematical Soc.|isbn=9780821851982 }}
*{{cite arXiv |last= Mikhalkin |first=Grigory |eprint=math/0601041v2 |title=Tropical Geometry and its applications |year=2006  }}
*{{cite arXiv |last= Mikhalkin |first=Grigory |eprint=math/0312530v4 |title=Enumerative tropical algebraic geometry in R2 |year=2004 }}
*{{cite arXiv |last= Mikhalkin |first=Grigory |eprint=math/0403015v1 |title=Amoebas of algebraic varieties and tropical geometry |year=2004  }}
*{{cite journal | last1=Pachter| first1=Lior | author1-link = Lior Pachter | last2=Sturmfels | first2=Bernd | author2-link=Bernd Sturmfels | title=Tropical geometry of statistical models|journal=[[Proceedings of the National Academy of Sciences of the United States of America]] | year=2004 | volume=101 | issue=46 | pages=16132–16137 | doi=10.1073/pnas.0406010101 | pmid=15534224 | pmc=528960 | zbl=1135.62302| arxiv=q-bio/0311009 | bibcode=2004PNAS..10116132P | doi-access=free }}
*{{cite arXiv |last= Speyer |first=David E. |eprint=math/0304218v3 |title=The Tropical Grassmannian |year=2003 }}
*{{cite journal |last1=Speyer |first1=David |last2=Sturmfels |first2=Bernd | author2-link=Bernd Sturmfels | arxiv=math/0408099 |title=Tropical Mathematics | orig-year=2004 | year= 2009 | zbl=1227.14051 | journal=[[Mathematics Magazine]] | volume=82 | number=3 | pages=163–173 | doi=10.4169/193009809x468760|s2cid=119142649 }}
*{{cite arXiv |last= Theobald |first= Thorsten |eprint=math/0306366v2 |title=First steps in tropical geometry |year=2003  }}
{{Refend}}

==Further reading==
* {{cite book | editor1-last=Amini | editor1-first=Omid | editor2-last=Baker | editor2-first=Matthew | editor3-last=Faber | editor3-first=Xander | title=Tropical and non-Archimedean geometry. Bellairs workshop in number theory, tropical and non-Archimedean geometry, Bellairs Research Institute, Holetown, Barbados, USA, May 6–13, 2011 | zbl=1281.14002 | series=Contemporary Mathematics | volume=605 <!-- | subseries=Centre de Recherches Mathématiques Proceedings -->|  location=Providence, RI | publisher=[[American Mathematical Society]] | isbn=978-1-4704-1021-6 | year=2013 }}
* [https://web.archive.org/web/20220116040726/https://www.math.utah.edu/~yplee/teaching/7800f15/Gross_Kansas_cropped.pdf Tropical geometry and mirror symmetry]

==External links==
* [https://archive.org/movies/details-db.php?id=4603 Tropical Geometry, I]

[[Category:Tropical geometry| ]]