Identical particles refer to those with identical intrinsic attributesparticle。 There are different kinds of particles in nature, such as electronsproton, neutronphoton、PionEtc.They can beElementary particle, or it can be composed of basic particlesComposite particle(e.gAlpha particle）。Take the electron for example, regardless of its source, according to experimental measurementStatic massAll areme=9.109534(±47)×10－31Kg ，The charge is -e[e=1.6021892 (± 46)×10－19C]，spinbyħ/2。Each particle has specific intrinsic attributes, includingStatic mass, charge, spinmagnetic moment, service life, etc.quantum mechanicsThe particles belonging to the same class with identical intrinsic properties are called identical particles.[1-2]
The Concept of Particle Homogeneity and Particle StatequantizationThere are essential connections.Without the quantization of states, there would be no homogeneity.Classical physicsSince the properties (mass, size, shape, etc.) of particles can change continuously, it is impossible to say that two particles are really the same.[1]
Multisystem composed of identical particlesHamiltonian, for any two particle exchange issymmetric(unchanged).Experiments show that the exchange of states of identical particle systemsSymmetry, depending on the spin of the particle.This homogeneity in quantum mechanics leads to identical multi particle systemswave functionFor the symmetry of particle exchange.For spin isħParticles with integral multiple (including 0), such asPion(spin is 0) andphoton(Spin isħ）, the wave function is symmetric for the exchange of any two identical particles (without changing the sign), calledBoson。For spin isħParticles, such as electrons, protons, and neutrons, whose spin isħ/2) , the wave function isAntisymmetryOf (changing the sign) calledFermion。[1-2]
Homogeneity of particles should not be considered as just oneabstract conception, it isObservable measurement。Identical fermion system must comply withPauli exclusion principleIt is to understand chemistryPeriodic law of elements（atomElectronic shell structure).After the emergence of quantum mechanics, this principle was theoretically proved on the basis of the principle of homogeneity.Pauli principleIt's atoms, molecules andNucleusOne of the theoretical foundations of structure.The identical boson system allows any number of particles to be in the samequantum stateUnder appropriate conditionsBose Einstein condensationPhenomenon.[1-2]
Specific description
Announce
edit
The existence of identical particles is a basic experimental fact in the objective material world and a basic theoretical belief widely accepted by the physics community.The charge of the electron is still taken as an example, although the experimental measurement is subject toaccuracyAnd each measurement result is in the last few digitsSignificant figuresHowever, most physicists still believe that the charge values of all electrons (including those that have not been measured) should be identical without any difference.Any physical theory, especiallyQuantum Theory, are based on this belief.[2]
A physical system composed of several identical particlesmotion state In principle, all properties ofElementary particle）Through the interaction with this system, we can find out one by one.If any two particles in the exchange system (NoiAndjBecause the particles exchanged are identical, the observation results of the external "observers" will obviously not be affected, so the particles must be considerediandjAfter the exchange, the system is still in the same state of motion.This point of view and the following wave functions are interchangeableSymmetryOr antisymmetry is usually called the principle of isotropy.For example, Ψ represents the wave function describing the system state before exchange.pijΨ represents the wave function of the system after exchange, Ψ andpijSince Ψ describes the same state, they differ by at most one constant factor.Since the wave function of two successive exchanges must be restored, the constant factor can only be ± 1.WhenpijΨ=+Ψ，The state of the system is said to be commutative symmetric;WhenpijΨ=－Ψ，Is called commutative antisymmetric.[2-3]
Experiments show that the exchange symmetry of the state of identical particle systems depends on the spin of particles. For identical particle systems whose spin is equal to an integral multiple of h - (0, h -, 2h -,...), the wave function is exchange symmetric and follows the Bose Einstein statistical law.Such particles are called bosons.All identical particle systems whose spin is equal to half integral times of h - (h -/2, 3h -/2,...), whose wave function is commutative antisymmetric and obeys the Fermi Dirac statistical rule, are called Fermions.Photon (spin h -), alpha particle pion (spin 0) is boson;Electrons, protons and neutrons (spin h -/2) are fermions.For the identical Fermion system, two or more particles cannot be in the same single particle state at the same time.That is, each single particle state can only contain one particle at most.This conclusion is calledPauli exclusion principle。The boson system is not limited by the Pauli principle. Moreover, because particles always spontaneously transition to lower energy levels, bosons tend to condense to ground state energy levels, which is the basic reason for low-temperature superconductivity and superfluidity.[4]
Important features
Announce
edit
Under the same conditions, their physical behaviors are identical, so replacing one identical particle with another will not cause changes in the physical state.stayclassical mechanicsIn, different particles can be distinguished from different tracks of particle motion.In quantum mechanicsWave particle duality, as time changes,waveThere is always overlap in the process of propagation, so identical particles are indistinguishable in quantum mechanics.It can be inferred from the principle of homogeneity thatHamiltonian operatorIt has commutative symmetry.
status
Announce
edit
Identical particle is one of the basic concepts of quantum mechanics.Refers to particles with identical intrinsic properties (mass, charge, spin, etc.).They can be basic particles or composite particles (such as alpha particles) composed of basic particles.
quantum mechanics
Announce
edit
Quantum mechanics is the theory of studying the motion law of microscopic particles, and is one of the theoretical foundations of modern physics.Quantum mechanics was established in the mid-1920s.At the end of the 19th century, people found that a large number of physical experimental facts could not be explained by the theory of complete continuity of energy in classical physics.In 1900, Planck, a German physicist, put forward the energy quantum hypothesis, which explained the energy distribution of blackbody radiation by quantizing the discontinuity of energy.In 1905, Einstein proposedlight quantum hypothesis It is the first time to reveal the wave particle duality of light and successfully explain the photoelectric effect.In 1906, Einstein used quantum theory to solve the specific heat problem of cryogenic solids.Then, Danish physicistsBohrA quantum theory to explain the atomic structure of atomic spectral lines was proposed, which was revised and generalized by German physicist Sommerfeld et al.In 1924, German physicistDe BroglieInspired by Einstein's photon hypothesis, the matter wave hypothesis was put forward, pointing out that all physical particles also have wave particle duality like light.In 1925, German physicists Heisenberg, Bohn and Jordan described the motion law of microscopic particles in the mathematical form of matrix and established matrix mechanics.Then, Austrian physicist Schrodinger described the motion law of microscopic particles in the form of wave equation, and established wave dynamics.Soon,SchrodingerIt is proved that these two kinds of mechanics are completely equivalent, which is today's quantum mechanics.Quantum mechanics uses wave functions to describe the motion state of microscopic particlesSchrodinger equationDetermine the change rule of wave function.When quantum mechanics is applied to solve the problems within the range of atoms and molecules, the results are consistent with the experiments;When quantum mechanics is applied to macroscopic objects or particles with considerable mass and energy, it can also draw the same conclusions as classical mechanics.Therefore, the establishment of quantum mechanics has greatly promoted atomic physics, solid state physics andNuclear physicsAnd promoted the application of new technologies such as semiconductor, laser and superconductor.It indicates that human cognition has gone deep into the micro field from the macro field.Quantum mechanics has opened up a new field for the development of philosophical research. It has proposed a series of new philosophical topics to people, such as the existence characteristics of micro objects, whether there is causality in the micro world, whether the subject and object are inseparable in principle, and the complementarity between the subject and object.Answering these questions in depth and correctly will undoubtedly promoteMarxist philosophyIn-depth development.
