# BookRiff

If you don’t like to read, you haven’t found the right book

## Is the Wigner function real?

This, naturally, is part of the appeal of phase space quantum mechanical calculations. While the Wigner function is real, unlike |Ψ(x)|2 and |˜Ψ(p)|2, it can take on negative values making it impossible to interpret it as a genuine probability distribution function.

## What is phase space quantum mechanics?

In dynamical system theory, a phase space is a space in which all possible states of a system are represented, with each possible state corresponding to one unique point in the phase space. For mechanical systems, the phase space usually consists of all possible values of position and momentum variables.

## Can the probability be negative?

The probability of the outcome of an experiment is never negative, although a quasiprobability distribution allows a negative probability, or quasiprobability for some events.

## What is the purpose of dividing phase space into cells?

Answer: It is, quite simply, the reason that statistical mechanics works when applied to classical systems. It is the reason we can divide up the continuous phase space into tiny cells, call each cell a microstate, and then treat them as if they were discrete.

## What is the spin of photon?

Electrons and quarks (particles of matter) can have a spin of –1/2 or +1/2; photons (particles of light) can have a spin of –1 or +1; and Higgs bosons must have a spin of 0. Though particle spins are tiny, they have an impact on our everyday world.

## Can probabilities be zero?

A probability of 0 means that the event will not happen. For example, if the chance of being involved in a road traffic accident was 0 this would mean it would never happen.

## What restricts the number of the particles that can occupy a phase space cell?

In phase space, the N/2 particles in each box are now restricted to a volume V/2, and their energy restricted to U/2, and the number of points describing a single microstate will change: the phase space description is not the same. This has implications in both the Gibbs paradox and correct Boltzmann counting.

## What is Liouville’s theorem in statistical mechanics?

Liouville’s theorem states that: The density of states in an ensemble of many identical states with different initial conditions is constant along every trajectory in phase space. is the density (number of particles per unit 2N-dimensional hypersphere.

## Why are photons spin 1?

Photons, which are the quanta of light, have been long recognized as spin-1 gauge bosons. The polarization of the light is commonly accepted as its “intrinsic” spin degree of freedom. Thus, the photon spin is always only connected to the two circular polarizations.