# Millennium Prize Problems

*https://en.wikipedia.org/wiki/Millennium_Prize_Problems*

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Millennium Prize Problems |
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The **Millennium Prize Problems** are seven problems in
mathematics that were stated by the
Clay Mathematics Institute on May 24, 2000.^{
[1]} The problems are the
Birch and Swinnerton-Dyer conjecture,
Hodge conjecture,
Navier–Stokes existence and smoothness,
P versus NP problem,
Poincaré conjecture,
Riemann hypothesis, and
Yang–Mills existence and mass gap. A correct solution to any of the problems results in a US$1 million prize being awarded by the institute to the discoverer(s).

To date, the only Millennium Prize problem to have been solved is the Poincaré conjecture, which was solved in 2003 by the Russian mathematician Grigori Perelman. He declined the prize money.

## Solved problem

### Poincaré conjecture

In dimension 2, a sphere is characterized by the fact that it is the only closed and simply-connected surface. The Poincaré conjecture states that this is also true in dimension 3. It is central to the more general problem of classifying all 3-manifolds. The precise formulation of the conjecture states:

Every simply connected, closed 3-manifold is homeomorphic to the 3-sphere.

A proof of this conjecture was given by
Grigori Perelman in 2003, based on work by
Richard Hamilton; its review was completed in August 2006, and Perelman was selected to receive the
Fields Medal for his solution, but he declined the award.^{
[2]} Perelman was officially awarded the Millennium Prize on March 18, 2010,^{
[3]} but he also declined that award and the associated prize money from the Clay Mathematics Institute. The Interfax news agency quoted Perelman as saying he believed the prize was unfair, as he considered his contribution to solving the Poincaré conjecture to be no greater than Hamilton's.^{
[4]}

## Unsolved problems

### P versus NP

The question is whether or not, for all problems for which an algorithm can *verify* a given solution quickly (that is, in
polynomial time), an algorithm can also *find* that solution quickly. Since the former describes the class of problems termed NP, while the latter describes P, the question is equivalent to asking whether all problems in NP are also in P. This is generally considered one of the most important open questions in
mathematics and
theoretical computer science as it has far-reaching consequences to other problems in
mathematics, and to
biology,
philosophy^{
[5]} and
cryptography (see
P versus NP problem proof consequences). A common example of an NP problem not known to be in P is the
Boolean satisfiability problem.

Most mathematicians and computer scientists expect that P ≠ NP; however, it remains unproven.^{
[6]}

The official statement of the problem was given by Stephen Cook.

### Hodge conjecture

The Hodge conjecture is that for projective algebraic varieties, Hodge cycles are rational linear combinations of algebraic cycles.

We call this the group of *Hodge classes* of degree 2*k* on *X*.

The modern statement of the Hodge conjecture is:

- Let
*X*be a non-singular complex projective manifold. Then every Hodge class on*X*is a linear combination with rational coefficients of the cohomology classes of complex subvarieties of*X*.

- Let

The official statement of the problem was given by Pierre Deligne.

### Riemann hypothesis

The Riemann zeta function ζ(s) is a function whose argument s may be any complex number other than 1, and whose values are also complex. It has zeros at the negative even integers; that is, ζ(s) = 0 when s is one of −2, −4, −6, .... These are called its trivial zeros. However, the negative even integers are not the only values for which the zeta function is zero. The other ones are called nontrivial zeros. The Riemann hypothesis is concerned with the locations of these nontrivial zeros, and states that:

- The real part of every nontrivial zero of the Riemann zeta function is 1/2.

The Riemann hypothesis is that all
nontrivial zeros of the analytical continuation of the
Riemann zeta function have a real part of ^{1}/_{2}. A proof or disproof of this would have far-reaching implications in
number theory, especially for the distribution of
prime numbers. This was
Hilbert's eighth problem, and is still considered an important open problem a century later.

The official statement of the problem was given by Enrico Bombieri.

### Yang–Mills existence and mass gap

In
quantum field theory, the **mass gap** is the difference in energy between the vacuum and the next lowest
energy state. The energy of the vacuum is zero by definition, and assuming that all energy states can be thought of as particles in plane-waves, the mass gap is the mass of the lightest particle.

For a given real field , we can say that the theory has a mass gap if the two-point function has the property

with being the lowest energy value in the spectrum of the Hamiltonian and thus the mass gap. This quantity, easy to generalize to other fields, is what is generally measured in lattice computations.

In physics, classical
Yang–Mills theory is a generalization of the Maxwell theory of
electromagnetism where the *chromo*-electromagnetic field itself carries charge. As a classical field theory it has solutions which travel at the speed of light so that its quantum version should describe massless particles (
gluons). However, the postulated phenomenon of
color confinement permits only bound states of gluons, forming massive particles. This is the
mass gap. Another aspect of confinement is
asymptotic freedom which makes it conceivable that
quantum Yang-Mills theory exists without restriction to low energy scales. The problem is to establish rigorously the existence of the quantum Yang–Mills theory and a mass gap.

- Prove that for any compact simple gauge group G, a non-trivial quantum Yang–Mills theory exists on and has a mass gap Δ > 0. Existence includes establishing axiomatic properties at least as strong as those cited in Streater & Wightman (1964), Osterwalder & Schrader (1973) and Osterwalder & Schrader (1975).

The official statement of the problem was given by
Arthur Jaffe and
Edward Witten.^{
[7]}

The
Navier–Stokes equations describe the motion of
fluids, and are one of the pillars of
fluid mechanics. However, theoretical understanding of their solutions is incomplete, despite its importance in science and engineering. For the three-dimensional system of equations, and given some initial conditions, mathematicians have not yet proven that
smooth solutions always exist. This is called the *
Navier–Stokes existence and smoothness* problem.

The problem, restricted to the case of an
incompressible fluid, is to prove either that smooth, globally defined solutions exist that meet certain conditions, or that they do not always exist and the equations break down. The official statement of the problem was given by
Charles Fefferman.^{
[8]}

### Birch and Swinnerton-Dyer conjecture

The Birch and Swinnerton-Dyer conjecture deals with certain types of equations: those defining elliptic curves over the rational numbers. The conjecture is that there is a simple way to tell whether such equations have a finite or infinite number of rational solutions. Hilbert's tenth problem dealt with a more general type of equation, and in that case it was proven that there is no way to decide whether a given equation even has any solutions.

The official statement of the problem was given by
Andrew Wiles.^{
[9]}

## See also

- Beal's conjecture
- Hilbert's problems
- List of mathematics awards
- List of unsolved problems in mathematics
- Smale's problems
- Paul Wolfskehl (offered a cash prize for the solution to Fermat's Last Theorem)

## References

**^**Arthur M. Jaffe "The Millennium Grand Challenge in Mathematics", " Notices of the AMS", June/July 2006, Vol. 53, Nr. 6, p. 652-660**^**"Maths genius declines top prize". BBC News. 22 August 2006. Retrieved 16 June 2011.**^**"Prize for Resolution of the Poincaré Conjecture Awarded to Dr. Grigoriy Perelman" (PDF) (Press release). Clay Mathematics Institute. March 18, 2010. Archived from the original (PDF) on March 31, 2010. Retrieved March 18, 2010.The Clay Mathematics Institute (CMI) announces today that Dr. Grigoriy Perelman of St. Petersburg, Russia, is the recipient of the Millennium Prize for resolution of the Poincaré conjecture.

**^**"Russian mathematician rejects million prize - Boston.com".**^**Scott Aaronson (14 August 2011). "Why Philosophers Should Care About Computational Complexity". Technical report.**^**William Gasarch (June 2002). "The P=?NP poll" (PDF).*SIGACT News*.**33**(2): 34–47. doi: 10.1145/1052796.1052804. S2CID 18759797.**^**Arthur Jaffe and Edward Witten " Quantum Yang-Mills theory." Official problem description.**^**Charles Fefferman. "Existence and Uniqueness of the Navier-Stokes Equation" (PDF). Clay Mathematics Institute.**^**Wiles, Andrew (2006). " The Birch and Swinnerton-Dyer conjecture". In Carlson, James; Jaffe, Arthur; Wiles, Andrew. The Millennium Prize Problems. American Mathematical Society. pp. 31–44. ISBN 978-0-8218-3679-8.

*This article incorporates material from Millennium Problems on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.*

## Sources

- Osterwalder, K.; Schrader, R. (1973). "Axioms for Euclidean Green's functions".
*Communications in Mathematical Physics*.**31**(2): 83–112. Bibcode: 1973CMaPh..31...83O. doi: 10.1007/BF01645738. - Osterwalder, K.; Schrader, R. (1975). "Axioms for Euclidean Green's functions II".
*Communications in Mathematical Physics*.**42**(3): 281–305. Bibcode: 1975CMaPh..42..281O. doi: 10.1007/BF01608978. - Streater, R.; Wightman, A. (1964).
*PCT, Spin and Statistics and all That*. W. A. Benjamin.

## Further reading

- Carlson, James;
Jaffe, Arthur;
Wiles, Andrew, eds. (2006).
*The Millennium Prize Problems*. Providence, RI: American Mathematical Society and Clay Mathematics Institute. ISBN 978-0-8218-3679-8. -
Devlin, Keith J. (2003) [2002].
*The Millennium Problems: The Seven Greatest Unsolved Mathematical Puzzles of Our Time*. New York: Basic Books. ISBN 0-465-01729-0.