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Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

6 votes
0 answers
105 views

Existence of large integer solution for a simple-looking equation

Is it true that for every $k>0$ Diophantine equation $$ y^2 + x^2y + z^2x + 1 = 0 $$ has an integer solution $(x,y,z)$ such that $\min\{|x|,|y|,|z|\}\geq k$? Motivation: this equation arises in the st …
Bogdan Grechuk's user avatar
22 votes
1 answer
984 views

On the smallest open Diophantine equations: beyond Hilbert's 10 problem

In 2018, Zidane asked What is the smallest unsolved Diophantine equation? The suggested way to measure size of the equation is substitute 2 instead of all variables, absolute values instead of all coe …
Bogdan Grechuk's user avatar
5 votes
2 answers
396 views

$x^3+x^2y^2+y^3=7$, and solvable families of Diophantine equations

(a) Do there exist integers $x$ and $y$ such that $x^3+x^2y^2+y^3=7$ ? (b) Is this equation belongs to some family $F$ of equations for which there is a known algorithms for testing if they have an i …
Bogdan Grechuk's user avatar
6 votes
5 answers
693 views

What are the integer solutions to $z^2-y^2z+x^3=0$?

The question is to describe ALL integer solutions to the equation in the title. Of course, polynomial parametrization of all solutions would be ideal, but answers in many other formats are possible. F …
Bogdan Grechuk's user avatar
0 votes
0 answers
149 views

Representing integers as sums of three powers

A famous open question, discussed several times on MathOverFlow, asks Which integers can be expressed as a sum of three cubes in infinitely many ways?. This is open even for $n=3$, that is, we do not …
Bogdan Grechuk's user avatar
9 votes
1 answer
686 views

Can $y^2-4$ be a divisor of $x^3-x^2-2 x+1$?

Do there exist integers $x$ and $y$ such that $\frac{x^3-x^2-2 x+1}{y^2-4}$ is an integer? In other words, can any integer representable as $x^3-x^2-2 x+1$ have any divisor representable as $y^2-4$? T …
Bogdan Grechuk's user avatar
10 votes
3 answers
680 views

Solve in integers: $y(x^2+1)=z^2+1$

Find all integer solutions to the equation $$ y(x^2+1)=z^2+1. $$ There is, for example, an infinite family of solutions $x=u$, $y=(uv\pm1)^2+v^2$, $z=(u^2+1)v \pm u$, $u,v \in {\mathbb Z}$, but there …
Bogdan Grechuk's user avatar
10 votes
1 answer
319 views

Positive integers such that $(x+y)(xy-1)=z^2+1$

Do there exist positive integers $x,y,z$ such that $$ (x+y)(xy-1)=z^2+1 $$ In my previous question Can you solve the listed smallest open Diophantine equations?, I discuss the smallest equations for w …
Bogdan Grechuk's user avatar
5 votes
1 answer
306 views

Are these equations solvable in positive integers?

By Matiyasevich theorem, there is no algorithm to decide whether a given Diophantine equation $P(x_1,\dots, x_n)=0$ has a solution in positive integers. As suggested in What is the smallest unsolved D …
Bogdan Grechuk's user avatar
2 votes
0 answers
35 views

Are there integers $x,y,z$ such that $1 + x - x^3 + x^2 y^2 + z + z^2 = 0$?

In my previous question Can you solve the listed smallest open Diophantine equations? I discuss the smallest equations (in some well-defined sense) for which it is not known whether they have any inte …
Bogdan Grechuk's user avatar
5 votes
0 answers
200 views

Are there integers $x,y,z$ such that $(x+1)y^2-xz^2=x^3+2x+2$?

Is equation $$ (x+1)y^2-xz^2=x^3+2x+2 $$ solvable in integers? Motivation: For a polynomial $P$ consisting of $k$ monomials of degrees $d_1,\dots,d_k$ and integer coefficients $a_1,\dots,a_k$, define …
Bogdan Grechuk's user avatar
8 votes
1 answer
495 views

Hilbert 10th problem for cubic equations

Hilbert 10th problem, asking for algorithm for determining whether a polynomial Diopantine equation has an integer solution, is undecidable in general, but decidable or open in some restricted familie …
Bogdan Grechuk's user avatar
5 votes
0 answers
326 views

On the shortest open cubic equation

The question is: are there any integers $x,y,z$ such that $$ 1+4 x^3+x y^2+2 y z^2 = 0 \quad\quad\quad\quad (1) $$ The motivation is: Define the length of a polynomial $P$ consisting of $k$ monomials …
Bogdan Grechuk's user avatar
65 votes
1 answer
6k views

Can you solve the listed smallest open Diophantine equations?

In 2018, Zidane asked What is the smallest unsolved Diophantine equation? The suggested way to measure size is substitute 2 instead of all variables, absolute values instead of all coefficients, and e …
Bogdan Grechuk's user avatar
1 vote
0 answers
424 views

How to describe all integer solutions to $x^2+y^2=z^3+1$?

The question is to find all integer solutions to the equation $$ x^2+y^2=z^3+1. $$ This equation obviously has infinitely many integer solutions (take, for example, $(x,y,z)=(1,u^3,u^2)$ for any integ …
Bogdan Grechuk's user avatar

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