THE POMERON: YESTERDAY, TODAY and TOMORROW

TL;DR

This paper reviews the historical development, current understanding, and future challenges of the Pomeron in high energy physics, covering Reggeon calculus, QCD approaches, and personal insights into unresolved problems.

Contribution

It provides a comprehensive overview of the Pomeron, integrating classical Regge theory with modern QCD perspectives and offering personal insights on future research directions.

Findings

Reggeon calculus laid the groundwork but has limitations.

QCD approaches offer a rigorous framework for high energy interactions.

Identifies future problems and directions in Pomeron research.

Abstract

These lectures are the review of the main ideas and approaches to the structure of the Pomeron. They are divided in three natural parts: (i) the brief review of the Reggeon Calculus, which was the first attempt to build the effective theory of the strong interaction at high energy. In spite of the fact that this approach turns out to be inconsistent and in lectures we show why, the Reggeon approach was and is the main source of the terminology and phenomenology for high energy ``soft" interactions. (ii) the detail description of the QCD approach to high energy interaction. We try to combine the rigorous approach in perturbative QCD with more simple, intuitive guess based on general properties of QCD to clarify our expectations and predictions. (iii) the outline of my personal opinion what problems will be important in the future. The main reason for the lectures was just the last part to agitate you to think about this difficult but because of that interesting problem. The motto of my lectures is {\it `` there is nothing more exciting than to solve a difficult problem. Pomeron is the one.''}