This chapter shows the math used in modern physics. It examines first relativity and then quantum mechanics. The discussion of special relativity opens with the Michelson-Morley experiment that disproved the existence of the ether. There is then a discussion of space-time and the idea of non-positive-definite metrics. Hyperbolic functions are examined and employed. Discussion of the space-time point of view leads to the twin paradox and its resolution. Examination of energy leads to E = mc 2 which rounds out special relativity. General relativity begins with examination of gravity which led Einstein to learn differential geometry and use it to describe motion in space-time with gravity. We then shift to quantum mechanics. We begin with particle-wave duality and from them follow Schrodinger's approach to generate his quantum wave equation. We then explore the meaning of solutions to Schrodinger's equation in terms of the probability distributions that they give rise to. We move on to Heisenberg's algebraic approach to quantum mechanics, including his uncertainty principle. We end with a discussion of quantum field theory and the question of what math will be needed to help unify modern physics.
This chapter shows the math used in modern physics. It examines first relativity and then quantum mechanics. The discussion of special relativity opens with the Michelson-Morley experiment that disproved the existence of the ether. There is then a discussion of space-time and the idea of non-positive-definite metrics. Hyperbolic functions are examined and employed. Discussion of the space-time point of view leads to the twin paradox and its resolution. Examination of energy leads to E = mc 2 which rounds out special relativity. General relativity begins with examination of gravity which led Einstein to learn differential geometry and use it to describe motion in space-time with gravity. We then shift to quantum mechanics. We begin with particle-wave duality and from them follow Schrodinger's approach to generate his quantum wave equation. We then explore the meaning of solutions to Schrodinger's equation in terms of the probability distributions that they give rise to. We move on to Heisenberg's algebraic approach to quantum mechanics, including his uncertainty principle. We end with a discussion of quantum field theory and the question of what math will be needed to help unify modern physics.
This paper takes a look at the two cornerstones of modern physics--Quantum Mechanics and The Theory of Relativity (Both Special and General). The differences and similarities for the two subjects are presented. More of their differences and similarities will emerge with new developments in physics. One can't rule out the possibility of the two being unified into one one fine day. That will herald another triumphant moment in physics. Introduction In 1905, Albert Einstein at the age of twenty-six formulated single-handedly, among others, the Theory of Special Relativity together with his other seminal papers on photoelectricity, Brownian motions of atoms and molecular dimensions. The year has been universally declared the Miraculous Year [1]. Ten years later, he came up with the theory of General Relativity--a new and revolutionary framework on gravity. Meanwhile in Europe a group of young physicists played pivotal role in the birth of Quantum Mechanics. Many of them went on to win Nobel prizes for their monumental contributions. Einstein also won the coveted prize not for Relativity but ironically for Photoelectric Effect. Irony has been part of physics in its history. Relativity with its weird 'Twin Paradox', constancy of the speed of light and the interchangebility between mass and energy (E=[mc.sup.2]) enthralls the public and scientists alike. It provides a way to measure particle masses [2]. The Quantum Theory has its fair share of weirdness and bewilderment. Both Quantum Mechanics and the Theory of Relativity bring forth new ideas in human thoughts. They are among Joanne Baker's 50 physics ideas [3]. Quantum Mechanics and the Theory of Relativity The quantum world where counterintuition reigns supreme is couched in uncertainty as epitomised by Heisenberg's uncertainty principle. Things do not behave in a deterministic way as enshrined and expected in classical Newtonian physics. The microscopic world of the electrons was dictated by randomness and indeterminacy. Albert Einstein was appalled by such dictates that he famously declared: 'God does not play dice with the universe.' The famous Danish physicist Neils Bohr sprang to his feet by saying: 'Stop telling God what to do with his dice.' The sparring between the two stalwarts in physics is legendary. According to Trefil [4], there are a couple of things that need to be said about the uncertainty principle: it does not imply that we cannot know either the position or the velocity of a particle, and it does not require the presence of a conscious mind. Marcus Chown [5] wraps up by saying 'The bitter irony, not lost on Einstein, was that he was the one who, by postulating the existence of the photon, had inadvertently set loose the genie of randomness of physics. The two theories of relativity by Einstein are not couched in randomness however. According to Smoot [6], both implied a radically new cosmology. Many people are of the opinion that with Einstein's theory of relativity, old classical physics is no more in vogue. According to Angier [7], Albert Einstein did not prove that Isaac Newton was wrong. Instead, he showed that Newton's theories of motion and gravity were incomplete, and that new equations were needed to explain the behavior of objects under extreme circumstances, such as when tiny particles travel at or near the speed of light. …
In the 20th century, two new terms were added to the scientific lexicon: relativistic mechanics and quantum mechanics. The challenge to the concept of the absoluteness of space and time started at the end of the 19th century and gave birth to Einstein's special relativity theory in 1905. This unified space and time to a single entity, space–time, and we have been introduced to many new concepts such as time dilation, space contraction, mass–energy relation, and the space–time continuum in relativity theory. We have also learned that the highest possible velocity in this universe is that of light and that nothing in the universe can move faster than light. Einstein's general theory of relativity took into consideration gravitation and established the chronogeometric concept of gravity. Quantum mechanics developed by Bohr, de Broglie, Heisenberg, Schrödinger, and others gave us knowledge in the atomic and subatomic domain and led to the wave–particle duality of de Broglie, the uncertainty principle of Heisenberg, the wave mechanics of Schrödinger, and so forth. We have learned that three distinct chords are at the heart of quantum mechanics—granularity, relational, and indeterminism. Although quantum mechanics is a weird subject, as we will discuss, the modern physics is totally based on it.
Abstract In the opening chapter on relativity, C. V. Vishveshwara (Vishu) takes the reader through an excursion on how Einstein laid down the remarkable foundations of special relativity. The chapter begins with an early treatment of relativity, namely Galilean relativity, which while successful with classical mechanics was not tenable with electromagnetism. Working in the seclusion of a patent office, Einstein thought deeply and despairingly of relativity that would encompass electromagnetism. He realized that not only spatial measures but also time varied among inertial observers moving with constant relative velocities. Thus, Einstein’s special theory of relativity came to be, and along with it, his celebrated equation, E = mc2. The chapter then surveys bizarre, observable consequences of this special relativity and how they all beautifully fit into a mathematical framework created by Minkowski in which space and time become united. The chapter concludes by describing physicists’ reactions to this radical new theory and its role in different areas, such as elementary particle physics and astrophysics. In the opening chapter of quantum physics, Smitha describes the circuitous historic path taken by many a physicist explorer that led to the establishment of its mind-boggling fundamentals. This revolutionary branch of physics was seeded by puzzles posed in the late 1800s related to the behavior of light from radiating objects. The chapter begins by exploring the nature of light and the story of blackbody radiation that led to Planck introducing the notion of the quantum. It then surveys the photoelectric effect, which heralds the concept of the photon, and wave-particle duality, which applies both to light and matter. The excursion continues into Schrödinger’s description of matter acting as a wave and its consequences, including energy quantization and quantum tunneling. The chapter then explains Heisenberg’s uncertainty principle from multiple angles. Finally, it presents the quantum picture of the atom and how it resolved some of the deep puzzles, a crowning testament to quantum theory.
Chapter 4 deals with Quantum Mechanical (QM) phenomena. The first section describes the first attempts at quantization of energy, momentum, angular momentum, etc. We start with Plank's solution to the black-body problem, introducing the concept of photons: discrete packets of electromagnetic energy. We show how Plank's description of black-body radiation is perfectly fit by the cosmic microwave radiation, providing the strongest evidence for the Big-Bang at the origin of the Universe. We then describe Bohr's solution to the paradoxical stability of atoms, introducing quantization of angular momentum (or action) and correctly predicting the energy levels of the hydrogen atom. We show how Einstein used Plank's idea to explain the photo-electric effect (an effect exploited in CCD cameras and solar cells) and how he used Bohr's understanding of energy levels in atoms to provide an intuitive explanation of Plank's law. Einstein insight opened the way to the field of spectroscopy and the development of the laser. In the second section, following the lead of Dirac, we show that QM is equivalent to Linear Algebra in the space of complex functions (which describe the state of the system). We show that Schrödinger's equation is a natural consequence of that description, once the relation between energy and frequency established by Plank (for photons) and de Broglie (for particles) is taken into account. In the context of the chiral ammonia molecule we discuss the queerness of QM which describes physical systems as superposition of states (such as left and right chirality state of a molecule, dead and alive cat). We show that this queerness is nonetheless supported by experiments and is behind much of our technology: masers and lasers, atomic clocks, semiconductors (diodes, transistors, etc.). In the following section we introduce the representation of operators in QM (the equivalent of matrices in linear algebra): momentum, position, energy, etc. which correspond to measurements on the system. We show that the non-commutability of some operators (common with matrix operations) leads to Heisenberg uncertainty principle: the position and momentum of a particle cannot be determined with absolute precision. We discuss the solution of Schrödinger's equation for free particles demonstrating their equivalence with EM phenomena: particles undergo refraction and diffraction, exemplifying the particle/wave duality inherent to QM systems. We discuss QM tunneling and its use in the Scanning Tunneling Microscope. In the following section we study Dirac's equation: the successful attempt by Dirac to unify QM with Einstein's relativity, with the resulting prediction of anti-particles and spin. We then solve for the energy levels of electrons in the hydrogen atom (from Schrödinger's equation) and show that the existence of spin profoundly affects the behavior of electrons in an atom: they cannot share the same energy level, a rule known as Pauli's exclusion principle. Pauli's principle is central to the understanding of the chemical properties of atoms and fully explains Mendeleev's periodic table of the elements. In the next section we discuss along with two exactly soluble systems (diatomic rotational and vibrational levels), various approximations used to study systems (e.g. molecules) for which there are no analytical solutions. In particular, we introduce Pauling's variational approach, Hückel molecular orbital theory and time independent perturbation theory. We apply those approaches to determine the energy levels in alkenes, in multi-electron atoms and in systems under constant electric or magnetic field (such as in Magnetic Resonance Imaging). In the last section we discuss time dependent perturbation theory. We use it to establish the rules allowing for transitions between energy levels and revisit Einstein description of absorption/emission phenomena.
Abstract Ontology is integral to the two most fundamental scientific theories of the twentieth century: quantum theory and the special and general theories of relativity. Issues that drove the development of quantum theory include the reality of quanta, the simultaneous wave- and particle-like nature of matter and energy, determinism, probability and randomness, Schrodinger’s wave equation, and Heisenberg’s uncertainty principle. So did the reality of the predictions about space, time, matter, energy, and the universe itself that were deduced from the special and general theories of relativity. Dirac’s prediction of antimatter based solely on the mathematics of his theory of the electron and Pauli’s prediction of the neutrino based on his belief in quantum mechanics are cases in point. Ontological interpretations of the uncertainty principle, of quantum vacuum energy fields, and of Schrodinger’s probability waves in the form of multiple universe theories further illustrate this point.
Quantum mechanics stands as one of the most profound and successful theories in the history of physics. This paper provides a comprehensive review of the foundational principles, mathematical formalism, and modern applications of quantum mechanics. Beginning with the historical development of the theory, we examine core postulates including wave-particle duality, the Heisenberg Uncertainty Principle, and the Schrödinger equation. We further explore quantum entanglement, quantum tunneling, and spin, and discuss their roles in cutting-edge technologies such as quantum computing, quantum cryptography, and quantum sensing. Diagrams and mathematical representations are included to aid conceptual clarity. This review aims to serve both as an educational reference and a bridge to current research frontiers.