# What is the anti commutator?

Contents

## What is the anti commutator?

When talking about fermions (pauli-exclusion principle, grassman variables θ1θ2=−θ2θ1), the commutators have to be adjusted accordingly (change the minus sign), thus become anti-commutators (in order to measure the same quantity).

**What is the commutator property?**

The commutator of two elements, g and h, of a group G, is the element. [g, h] = g−1h−1gh. This element is equal to the group’s identity if and only if g and h commute (from the definition gh = hg [g, h], being [g, h] equal to the identity if and only if gh = hg).

### Why are commutators useful?

Commutators and brushes are used on all DC generators and DC motors. On DC and most AC motors the purpose of the commutator is to insure that the current flowing through the rotor windings is always in the same direction, and the proper coil on the rotor is energized in respect to the field coils.

**What is the commutator of two operators?**

The Commutator of two operators A, B is the operator C = [A, B] such that C = AB − BA. If the operators A and B are scalar operators (such as the position operators) then AB = BA and the commutator is always zero.

## What does a commutator do?

Note: In a generator, a commutator results in an output of direct current. In a motor, the commutator converts incoming alternating current into direct current before using it to generate motion.

**What does the commutator tell you?**

A commutator in quantum mechanics tells us if we can measure two ‘observables’ at the same time. If the commutator of two ‘observables’ is zero, then they CAN be measured at the same time, otherwise there exists an uncertainty relation between the two.

### Is a commutator Hermitian?

=> the commutator of hermitian operators is an anti hermitian operator. And an antihermitian operator is an hermitian operator times i. [A,B] = iC just relates this fact nothing more.

**How does a commutator work?**

A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. By reversing the current direction in the rotating windings each half turn, a steady rotating force (torque) is produced.

## What if the commutator is zero?

If the commutator of two ‘observables’ is zero, then they CAN be measured at the same time, otherwise there exists an uncertainty relation between the two. Going back to the Heisenberg example, taking a measurement of the position of a particle will disturb its momentum.

**How do you find the commutator?**

The order of the operators is important. The commutator [A,B] is by definition [A,B] = AB – BA. [A,BC] = B[A,C] + [A,B]C and [AB,C] = A[B,C] + [A,C]B. Proof: [A,BC] = ABC – BCA + (BAC – BAC) = ABC + B[A,C] – BAC = B[A,C] + [A,B]C.

### How to calculate the properties of an anti commutator?

$$ [AB,C] = ABC-CAB = ABC-ACB+ACB-CAB = A[B,C] + [A,C]B. $$ Notice that $ACB-ACB = 0$, which is why we were allowed to insert this after the second equals sign. Now let’s consider the equivalent anti-commutator $\\lbrace AB , Cbrace$; using the same trick as before we find

**How to find properties of anticommutators of operators?**

Do anticommutators of operators has simple relations like commutators. For example: $$[AB,C]=A[B,C]-[C,A]B.$$ But I don’t find any properties on anticommutators. Do same kind of relations exists… Stack Exchange Network

## When to use commutator and anticommutator in ring theory?

Ring theory. The anticommutator of two elements a and b of a ring or an associative algebra is defined by Sometimes the brackets [ ] + are also used to denote anticommutators, while [ ] − is then used for commutators. The anticommutator is used less often than the commutator, but can be used, for example, to define Clifford algebras,…

**What are the properties of anticommutators in quantum mechanics?**

Properties of anticommutators [closed] Ask Question Asked4 years, 4 months ago Active3 years, 7 months ago Viewed21k times 3 5 $\\begingroup$ Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it’s on-topicfor Physics Stack Exchange.