Albert Einstein proposed the theory of relativity at the beginning of the 20th century.
Theoretical physics is a branch of physics that deals with the development and formulation of mathematical models and theories to describe and predict the behavior of systems. It is based on fundamental principles and laws to build coherent theoretical frameworks that explain observable phenomena in the universe.
Theoretical physicists use advanced mathematical tools and abstract reasoning to derive predictions that can be tested through experiments or observations. This discipline is necessary for the advancement of knowledge in physics and has been crucial in the development of modern technologies and our understanding of the universe at scales from the microscopic to the cosmic.
Relativity
The theory of relativity, proposed by Albert Einstein at the beginning of the 20th century, consists of two main formulations: the theory of special relativity and the theory of general relativity.
special relativity
Published by Einstein in 1905, it revolutionized our understanding of space, time and speed. It postulates that the laws of physics are the same for all observers who move at constant speed relative to each other. It introduces concepts such as time dilation and length contraction, and establishes the famous equation E=mc 2 , which relates energy (E) to mass (m and the speed of light (c).
General relativity
Also known as the theory of gravitation , it was published by Einstein in 1915 and extends the principles of special relativity to include gravity . It provides a geometric description, where the presence of mass and energy bends the fabric of space-time , thus affecting the trajectory of moving objects. General relativity predicts phenomena such as the bending of light around massive objects (gravitational lenses) and gravitational waves.
Relativistic and non-relativistic theories
Relativistic quantum theories
They try to unify the principles of quantum mechanics with the theory of special or general relativity. Notable examples include quantum electrodynamics (QED) and quantum chromodynamics (QCD), which describe strong electromagnetic and nuclear interactions, respectively, within the framework of special relativity.
Non-relativistic theories
They describe systems where the speed of particles is much lower than that of light, so relativistic effects can be ignored with sufficient precision. A common example is non-relativistic quantum mechanics, which describes the behavior of subatomic particles under non-relativistic conditions, such as electrons in atoms.
Particle physics focuses on elementary particles and the forces responsible for their interactions and behavior.
particle physics
Particle physics studies elementary particles and the fundamental forces that govern their behavior and the interactions between them. Below we define some key concepts.
Elementary particles
The fundamental units of matter and energy. They are divided into two categories: fermions , which include quarks and leptons , and bosons , which carry fundamental forces. Examples of elementary particles are the electron , the up quark, the photon , and the Higgs boson .
Virtual particles
They temporarily exist as mathematical solutions in certain quantum field theory calculations, but are not detected as real particles. They are important to understand and calculate the interactions between the latter.
Fundamental interactions
The basic forces that govern the interactions between elementary particles. They include gravitational interaction, electromagnetic interaction, strong nuclear interaction, and weak nuclear interaction.
Strong interactions
The strong nuclear interaction is one of the four fundamental interactions and is responsible for holding the nucleons together in the atomic nucleus . It is transmitted through particles called gluons, which interact with the quarks that make up protons and neutrons. The strong interaction is very powerful at short distances , but decreases rapidly as distances increase, resulting in the confinement of quarks within hadrons and the formation of stable atomic nuclei.
Wave-particle duality
A fundamental principle of quantum mechanics that states that all subatomic particles, such as electrons and photons, can behave as point particles with a defined location in space and precise moment, but can also exhibit wave behaviors , such as diffraction and interference. This essential duality challenges our classical intuition about the nature of matter and light, and is fundamental to understanding quantum phenomena such as the Heisenberg uncertainty principle .
Related theories
string theory
It proposes that fundamental particles are not dimensionless points, but rather one-dimensional objects called strings. This theory seeks to provide a unified description of all the fundamental forces of nature.
Cosmic inflation theory
It proposes that shortly after the Big Bang, the universe experienced a rapid period of exponential expansion. This would help explain several observed aspects of the cosmos, such as the uniformity in the distribution of matter and the microwave background radiation.
Quantum information theory
It focuses on the study of information in the context of quantum mechanics. It examines how information can be encoded, transmitted and manipulated in quantum systems, and has important implications for cryptography and quantum computing .
Disturbance theory
In the context of quantum fields, perturbation theory is a method of calculating approximations to physical quantities, such as energies or transition probabilities, by introducing small perturbations to a known solution.
Quantum theory of gravity
It is an attempt to combine quantum mechanics and the theory of general relativity to describe gravitational phenomena on very small scales, such as inside black holes or during the first moments of the Big Bang. It is still an area of active research and a completely satisfactory theory has not been reached.
Cosmology studies the origin, evolution and structure of the universe.
Cosmology
Cosmology , in the context of theoretical physics, is the study of the origin, evolution, and structure of the universe as a whole. It is based on theoretical models supported by astronomical observations and cosmological experiments. Some key concepts in cosmology in relation to theoretical physics include:
Standard cosmological model
It describes the evolution of the universe from its origin in the Big Bang to its current state. It is based on Einstein's theory of general relativity and astronomical observations, such as the expansion of the universe and microwave background radiation. It includes the theory of cosmic inflation and the formation of large-scale structures through ordinary matter and radiation .
dark matter
A form of matter that does not emit, absorb, or reflect electromagnetic light, so it is not directly observable with traditional astronomical methods. However, its presence is inferred from gravitational effects observed in galaxies and galaxy clusters . The precise nature of dark matter is not yet fully understood, and it is the subject of active research in theoretical and experimental physics.
dark energy
A form of energy that is believed to permeate all of space and contribute to the acceleration of the expansion of the universe. Unlike dark matter, which has gravitational effects on cosmological scales, dark energy acts as a kind of negative pressure that counteracts the gravitational pull of ordinary matter. Its exact nature remains one of the greatest mysteries in cosmology and theoretical physics, and its understanding is fundamental to understanding the ultimate fate of the universe.