# What is Heisenberg: Definition and 308 Discussions

Werner Karl Heisenberg (; German pronunciation: [ˈvɛɐ̯nɐ ˈhaɪzn̩ˌbɛɐ̯k] (listen); 5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the key pioneers of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, this matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. Heisenberg was awarded the 1932 Nobel Prize in Physics "for the creation of quantum mechanics".Heisenberg also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles. He was a principal scientist in the German nuclear weapons program during World War II. He was also instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957.
Following World War II, he was appointed director of the Kaiser Wilhelm Institute for Physics, which soon thereafter was renamed the Max Planck Institute for Physics. He was director of the institute until it was moved to Munich in 1958. He then became director of the Max Planck Institute for Physics and Astrophysics from 1960 to 1970.
Heisenberg was also president of the German Research Council, chairman of the Commission for Atomic Physics, chairman of the Nuclear Physics Working Group, and president of the Alexander von Humboldt Foundation.

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1. ### I Heisenberg Equations of Motion for Electron in EM-field

Consider the Heisenberg picture Hamiltonian $$H(t) = \int_{\textbf{r}}\psi^{\dagger}(\textbf{r},t)\frac{(-i\hbar\nabla+e\textbf{A})^{2}}{2m}\psi(\textbf{r},t)$$ where ##\psi(\textbf{r},t)## is a fermion field operator. To find the equations of motion that ##\psi,\psi^{\dagger}## obey. I would...

8. ### I The clarity of Heisenberg uncertainty

We know from basic quantum mechanics that the Heisenberg uncertainty states that position and momentum can not be measured simultaneously with arbitrary precision. My question is, is this relation is due to the nature of the quantum system itself, or "merely" unbreachable limitation to our...
9. ### I Does Heisenberg Have Ontological Commitments to Quantum Theory?

Heisenberg is regarded as a major figure of the Copenhagen interpretation. In a certain degree, he is influenced by Logical positivism. Despite of that, has he any ontological commitments regarding the Quantum theory? Or, he considers the Quantum theory merely as calculation procedure for...
10. ### A Expectation value in Heisenberg picture: creation and annihilation

So, I have a hamiltonian for screening effect, written like: $$H=\sum_{k}^{}\epsilon_{k}c_{k}^{\dagger}c_{k}+ \frac{1}{\Omega}\sum_{k,q}^{}V(q,t)c_{k+q}^{\dagger}c_{k}$$ And I have to find an equation for the time evolution of the expected value of the operator ##c_{k-Q}^{\dagger}c_{k}##. I...
11. ### A SO(3) group, Heisenberg Hamiltonian

We have commutation relation ##[J_j,J_k]=i \epsilon_{jkl}J_l## satisfied for ##2x2##, ##3x3##, ##4x4## matrices. Are in all dimensions these matrices generate ##SO(3)## group? I am confused because I think that maybe for ##4x4## matrices they will generate ##SO(4)## group. For instance for...
12. ### I Heisenberg Uncertainty Principle Violation?

Hello, 2 questions please about the Uncertainty Principle and the following scenario: I shoot at each other, 2 electrons each with equal but opposite velocity such that they repel each other? (To me, this indicates that you know the momentum of each electron and you know each position...
13. ### I Heisenberg on ''uncertainty relation does not apply to the past''

In post #30 of a now closed thread, vanhees71 wrote: The quote in question is from his 1930 book "The Physical Principles of the Quantum Theory" on p.20 of the English translation of the German original. There Heisenberg writes:
14. ### A Heisenberg lens and probabilities

Hi Pf in her experiment Birgit Dopfer uses an https://www.researchgate.net/figure/color-online-The-Dopfer-experiment-of-the-Zeilinger-Group-Innsbruck-If-detector-D2-is_fig7_265787833 the distance between the source and the lens is 2f and the detector may be at the distance f or 2f behind the...
15. ### I Applying Heisenberg picture to density operator

Suppose that a particle evolves from point A to point B. The state of the particle can be written as $$\rho=\sum \left | m\right >\rho_{mn}\left< n\right | .$$ Because the basis is evolving as the particle travels, I am considering applying the Heisenberg picture to the density operator. Let...
16. ### A Heisenberg equation of motion -- Partial derivative question

Heisenberg equation of motion for operators are given by i\hbar\frac{d\hat{A}}{dt}=i\hbar\frac{\partial \hat{A}}{\partial t}+[\hat{A},\hat{H}]. Almost always ##\frac{\partial \hat{A}}{\partial t}=0##. When that is not the case?
17. ### A Heisenberg Uncertainty Relation for mixed states

How do you prove Heisenberg uncertainty relations for mixed states (density matrix), only from knowing the relation is true for pure states?
18. ### I Quantities in the Heisenberg Uncertainly Principle

Hello, I am a Brazilian Physics student and would like to ask a question. Why are not all physical quantities related to each other by the degree of precision in the Heisenberg Uncertainty Principle? For example, why is it possible to determine the energy and position of a particle without its...
19. ### I Heisenberg Microscope: Exploring Single Photon Diffraction

In the thought experiment proposed by Heisenberg, a single photon is scattered by the electron that we want to observe, and entering the microscope lens (the photon), it will create a diffraction pattern that gives the uncertainty on the position according to the law of optics. I wanted to ask...
20. ### I Pros and cons of Heisenberg and Schrodinger (and Feynman) pictures?

So there's this professor who insists that the Heisenberg picture is all the rage and much superior in most ways to the Schrodinger picture. He compares it to how you don't use the Hamilton-Jacobi formulation of classical mechanics as much as the Hamiltonian one. Alright, I can buy it. I...
21. ### I Virtual particles and Heisenberg

Hi people. Having as uncertainty principle that ΔE Δt≥ h/4Pi, why Δt≤ h/4PiΔE to allow the existence of a virtual particle? How ≥ becomes ≤ ? I think... real particles must obey ≥ so any particle that do not obey that is a virtual particle and thus why virtual particle needs to obey Δt≤...
22. ### I Understanding the meaning of "uncertainty" in Heisenberg's UP

Hi! I am checking Zettili's explanation on the uncertainty principle and I have this confusion on what the "uncertainty" really means which arises from the following statements: When introducing the uncertainty principle, for the case of position and momentum it states that: if the x-component...
23. ### Stability of Classical Heisenberg Spins (Equation of Motion)

Consider the classical Heisenberg model without an external field which is defined by the Hamiltonian: \mathcal{H} = -\sum_{ij} J_{ij} \vec{s_i}\vec{s_j} where J_{ij} > 0 describes the coupling between the spins \vec{s}_i \in \mathbb{R}^3 on some lattice. (Is there a way to use tex...
24. ### A Heisenberg equations of Klein-Gordon Field in Space-Time

Hi, there. I am reading An Introduction to Quantum Field Theory by Peskin and Schroeder. I am confused about some equations in section 2.4 The Klein-Gordon Field in Space-Time. It computes the Heisenberg equations of ##\phi \left ( x \right )## and ##\pi \left ( x \right)## as (in page 25) ##...
25. ### Heisenberg and Varying the Velocity

Good Morning When we derive the Euler Lagrange equations using Hamilton's Principle, we make a point of varying the velocity and the position at the same time, (despite the fact that, normally, they are related through a derivative). I do understand that this is allowed: we are trying to find...
26. ### How to calculate an operator in the Heisenberg picture?

I have some problems when calculating the operators in Heisenberg picture. First, ##\frac {dx} {dt} = \frac {1} {i \hbar} \left [ x, H \right ] = \frac {p} {m}##. Similarly, ##\frac {dp} {dt} = \frac {1} {i \hbar} \left [ p, H \right ] = - m \omega ^ 2 x##. These are coupled equations. I...
27. ### I What did Heisenberg know about the measurement problem?

While reading a book "Physics and Philosophy: The Revolution in Modern Science." by Werner Heisenberg, 1958, I was much surprised by the following passage near the end of Chapter 3: "The measuring device deserves this name only if it is in close contact with the rest of the world, if there is...
28. ### I Quantum Measurement under Heisenberg Picture?

When a quantum measurement occurs under the Schrodinger picture, the wave function collapses to one of the eigenvectors of the operator-observable and the value measured is the corresponding eigenvalue of that eigenvector. What happens during a quantum measurement under the Heisenberg picture...
29. ### I Heisenberg Uncertainty: simple explanation required please

why can't we know where electron goes after it was hit by light? Light has a travel direction, can't we assume that electron bounces to the same direction that the light was headed??
30. ### I What is the name for the Heisenberg uncertainty principle?

In quantum mechanics the name is Uncertainty principle. But outside of QM, what is the name for those inequalities?
31. ### A What is the Corrected Heisenberg Limit for Phase Estimation Measurements?

A 2019 paper by Gorecki et al. derives an uncertainty principle limit that is larger than the conventional Heisenberg limit by a factor of ##\pi##: https://arxiv.org/abs/1907.05428 I'm wondering if any QM experts have seen this and what your thoughts are.
32. ### A Mean field theory in the Heisenberg model

I have a problem about Heisenberg model.When applying mean field approximation,why does the average of spin flip terms be zero(<S+>=<S-> = 0 )? Thanks
33. ### I Interpretation of QM in the Heisenberg Picture

This is in reference to a question, never fully resolved, posed here: https://www.physicsforums.com/threads/interpretation-of-the-heisenberg-picture-in-qm.816449/ The von Neumann postulates for Quantum Theory - Evolution (Schrödinger's equation) and Projection (Born's rule) are always framed...