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tamnd's digital brain — notes, problems, research

42744 notes

Post-Quantum Cryptography

Modern public-key cryptography relies heavily on two computational assumptions:

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The Langlands Program

The Langlands program is one of the most ambitious and influential theories in modern mathematics.

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Exponential Sums

Exponential sums are among the central tools of analytic number theory.

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Valuations and Absolute Values

In ordinary analysis, the absolute value

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Dedekind Domains

Ordinary integers satisfy several remarkable properties simultaneously:

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Suggested Projects and Explorations

Study empirical properties of prime numbers through computation.

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Lattice Cryptography

Lattice cryptography is a family of cryptographic systems based on the presumed hardness of computational problems on high-dimensional lattices.

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Circle Method

Many problems in additive number theory ask whether an integer can be represented in the form

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Automorphic Representations

Classical modular form theory begins with analytic functions satisfying symmetry conditions.

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Principal Ideals

Let $R$ be a commutative ring. An ideal $I\subseteq R$ is called principal if there exists an element $\alpha\in R$ such that

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Waring's Problem

Waring's problem asks whether every sufficiently large positive integer can be written as a sum of a bounded number of fixed powers.

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Pairing-Based Cryptography

Pairing-based cryptography uses special maps defined on elliptic curve groups. A pairing is a function

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Automorphic Forms

Modular forms are functions on the upper half-plane satisfying symmetry conditions under the modular group

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Discriminants

The discriminant is one of the most important invariants of a number field. It measures how the arithmetic of the field differs from ordinary rational arithmetic.

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Goldbach Problems

Goldbach-type problems ask whether integers can be represented as sums of primes. They are among the oldest and most famous problems in additive number theory.

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Elliptic Curve Cryptography

Elliptic curve cryptography is a public-key cryptographic framework based on the arithmetic of elliptic curves over finite fields.

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The Modularity Theorem

For centuries, elliptic curves and modular forms were studied as separate objects.

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Units and Dirichlet Unit Theorem

Let $K$ be a number field and let

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Class Groups

In ordinary integers, every ideal is generated by a single element:

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Diffie-Hellman Key Exchange

Secure communication requires two parties to share secret information. In classical symmetric cryptography, both parties must already possess the same secret key before...

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Sumsets

Additive number theory studies arithmetic structure through addition of integers and subsets of integers.

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Elliptic Curves and Modularity

An elliptic curve is simultaneously:

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Problem Sets

1. Prove that the sum of two even integers is even.

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Generalized Riemann Hypothesis

The classical Riemann Hypothesis concerns the zeros of the Riemann zeta function

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Ideals and Prime Ideals

In ordinary integers, every number factors uniquely into primes. In many rings of algebraic integers, this property fails.

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Unique Factorization Failure

One of the central properties of the ordinary integers is unique factorization.

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Norm and Trace

Let $K$ be a number field of degree

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RSA Cryptosystem

Classical cryptography uses a shared secret key. Both sender and receiver must know the same secret information in advance.

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Modular Curves

The modular group acts on the upper half-plane by fractional linear transformations:

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Nonvanishing Results

A central theme in analytic number theory is determining when an $L$-function is nonzero at a particular point.

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Symbolic and Numeric Computation

Modern number theory relies heavily on computation. Two broad computational paradigms dominate the subject:

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Primes in Arithmetic Progressions

An arithmetic progression is a sequence of the form

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Hecke Operators

Modular forms already possess symmetry under the modular group. Yet a deeper arithmetic structure emerges through another family of operators: the Hecke operators.

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Ring of Integers

In ordinary arithmetic, the integers

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Dirichlet $L$-Functions

The Riemann zeta function

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Algorithms for Elliptic Curves

Elliptic curves occupy a central position in modern number theory, arithmetic geometry, and cryptography.

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Cusp Forms

Modular forms satisfy strong symmetry conditions under the modular group. Among them, cusp forms form the deepest and most arithmetic subclass.

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Algorithms for Modular Forms

Modular forms are highly structured analytic functions with deep arithmetic properties. Although their definitions involve complex analysis and group actions, modular forms...

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Eisenstein Series

Among all modular forms, Eisenstein series are the most explicit and computationally accessible.

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Orthogonality Relations

Dirichlet characters behave analogously to exponential functions in Fourier analysis. Just as complex exponentials separate frequencies, characters separate residue classes...

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Number Fields

A number field is a finite extension of the rational numbers. Concretely, it is a field $K$ satisfying

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Modular Forms

Modular forms are among the central objects of modern number theory.

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Lattice Reduction

A lattice is a discrete additive subgroup of Euclidean space. More concretely, let

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Chronology of Number Theory

| Period | Development |

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Dirichlet Characters

The Riemann zeta function studies prime numbers globally, without distinguishing congruence classes. However, many arithmetic questions concern primes satisfying conditions such as

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Modular Functions

The modular group acts on the upper half-plane by fractional linear transformations:

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Minimal Polynomials

An algebraic number is a complex number that satisfies some nonzero polynomial equation with rational coefficients. Thus $\alpha\in\mathbb{C}$ is algebraic if there exists a...

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Index of Definitions

| Definition | Location |

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Connections with Prime Distribution

The Riemann zeta function was introduced through the series

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Integer Factorization

Integer factorization asks for the prime decomposition of a positive integer. Given

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Euler Products

Euler products are one of the central ideas of analytic number theory. They express infinite sums over integers as infinite products over primes.

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Dirichlet Series

An arithmetic function $fn$ can be encoded into an infinite series of the form

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Modular Groups

Modular forms begin with the action of certain matrix groups on the complex upper half-plane.

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Algebraic Integers

The ordinary integers

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Index of Theorems

| Theorem | Location |

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Primality Testing

A prime number is an integer greater than $1$ whose only positive divisors are

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Global Class Field Theory

One of the central goals of algebraic number theory is to classify field extensions of a number field

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Explicit Formulae

One of the deepest ideas in analytic number theory is that the zeros of the zeta function determine the distribution of prime numbers.

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Diophantine Approximation

Diophantine approximation studies how closely real numbers can be approximated by rational numbers.

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Average Orders of Arithmetic Functions

Arithmetic functions often fluctuate strongly from one integer to the next.

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Möbius Inversion

Many arithmetic functions are defined through sums over divisors. For example,

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Pell Equations via Continued Fractions

Recall that a Pell equation has the form

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Riemann Hypothesis

The Riemann zeta function has nontrivial zeros inside the critical strip

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Fast Integer Arithmetic

Modern computational number theory depends fundamentally on efficient arithmetic with large integers.

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Local Class Field Theory

Global class field theory studies finite abelian extensions of number fields such as

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Dirichlet Convolution

Arithmetic functions can be added and multiplied pointwise, but number theory has another product that is better adapted to divisibility.

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Convergents

The convergents of a continued fraction are the rational numbers obtained by truncating the expansion at finite stages.

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Zeros of the Zeta Function

The zeros of the Riemann zeta function are the complex numbers $s$ satisfying

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Notation Index

| Symbol | Meaning |

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Trace Formula

One of the central ideas of modern analysis is that functions may be decomposed spectrally into elementary pieces.

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Hilbert Class Fields

One of the central discoveries of algebraic number theory is that unique factorization may fail in rings of algebraic integers.

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Functional Equation

The defining series of the zeta function,

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Rational Approximations

Many important numbers are irrational:

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Completely Multiplicative Functions

An arithmetic function is a function defined on the positive integers. Such a function

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Liouville Function

The Liouville function is an arithmetic function denoted by

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Analytic Continuation

The defining series of the Riemann zeta function is

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Reciprocity Maps

One of the oldest themes in number theory is reciprocity: the phenomenon that solvability conditions for one prime are controlled by arithmetic involving another prime.

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Infinite Continued Fractions

Finite continued fractions correspond exactly to rational numbers. When the Euclidean algorithm never terminates, the continued fraction becomes infinite.

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Functoriality

Functoriality is the unifying mechanism of the Langlands program. It predicts systematic relationships between automorphic representations attached to different algebraic groups.

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Euler Totient Function

Euler's totient function is an arithmetic function denoted by

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Euler Product Formula

The defining series of the Riemann zeta function is

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Abelian Extensions

A central goal of algebraic number theory is to understand field extensions of a given base field, especially extensions of the rational numbers

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Finite Continued Fractions

A finite continued fraction is an expression of the form

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Glossary

A group $G$ is abelian if

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Definition of the Zeta Function

One of the central objects of analytic number theory is the Riemann zeta function. It connects infinite series, prime numbers, complex analysis, and arithmetic structure into...

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Euclidean Algorithm Revisited

The Euclidean algorithm is one of the oldest and most important algorithms in mathematics. It computes the greatest common divisor of two integers using repeated division.

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Adeles and Ideles

The rational numbers may be studied through their completions:

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Möbius Function

The Möbius function is an arithmetic function denoted by

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Langlands Program

The Langlands program is a broad collection of conjectures connecting number theory, representation theory, harmonic analysis, and algebraic geometry. Its central idea is that...

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Twin Prime Heuristics

A pair of primes

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Computational Aspects

Quadratic residue theory is not only a theoretical subject. It also plays a major role in computational number theory, cryptography, primality testing, and algorithm design.

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Local-Global Principles

A central problem in number theory is determining whether an equation possesses rational or integral solutions.

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Appendix J. Historical Notes and Bibliography

Number theory is one of the oldest parts of mathematics, but modern number theory is not a single ancient subject carried forward unchanged. It is a layered discipline....

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Divisor Functions

Divisor functions measure the positive divisors of an integer. They are among the first examples of arithmetic functions, because their values depend directly on the prime...

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Applications to Computation

Modular arithmetic is not only a theoretical language for divisibility. It is also one of the main tools of computation with integers.

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Prime Gaps

Let

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Adelic Methods

Number theory studies arithmetic simultaneously at two levels:

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Higher Reciprocity Laws

Quadratic reciprocity describes when one prime is a square modulo another prime. A natural question is whether similar laws exist for higher powers.

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Hensel’s Lemma

One of the central ideas of number theory is that congruences modulo powers of a prime often approximate genuine arithmetic solutions.

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Fast Modular Exponentiation

Modular arithmetic often requires computing powers such as

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