# Are energy bands in solid state timeless?

• B
• jake jot
In summary, the Schroedinger equation is time symmetric in nonrelativistic quantum mechanics and applies to all systems, whether it is a single particle or a solid crystal lattice. However, when a measurement is made, only a small amount of information is acquired due to the collapse of the wave function. This has led to debates about the time symmetry of quantum mechanics and its implications for causality. While some argue that the laws of quantum mechanics are time symmetric, others believe that measurement introduces a direction of time. This topic remains open for interpretation and further research.
jake jot
The wave function or Schroedinger equation is timeless, correct? You can reverse the equations and forward it.

Our arrow of time comes due to decoherence in macroscopic object.

How about energy bands in solid state. Do you consider it as timeless wave function, or is it decohered?

Delta2
The Schroedinger equation tells you how the wave function changes with time. I'm not sure what you mean by "timeless". It's time symmetric (in nonrelativistic quantum mechanics). It doesn't matter if you consider a particle in a box, or 1027 particles, or the band structure in a solid.

mfb said:
The Schroedinger equation tells you how the wave function changes with time. I'm not sure what you mean by "timeless". It's time symmetric (in nonrelativistic quantum mechanics). It doesn't matter if you consider a particle in a box, or 1027 particles, or the band structure in a solid.

Time symmetric is not the same as our macroscopic time. So an electron wave function in a solid treads upon the imaginary as well as future and past domains, linking and coupling all these regions with one another. Information can pass from one of these domains into the other. Is this correct? Something we can't do with our unsymmetric time (due to arrow of time introduced by decoherence).

Motore and Delta2
jake jot said:
Time symmetric is not the same as our macroscopic time. So an electron wave function in a solid treads upon the imaginary as well as future and past domains, linking and coupling all these regions with one another. Information can pass from one of these domains into the other. Is this correct?

That doesn't sound correct at all.

Delta2
jake jot said:
Time symmetric is not the same as our macroscopic time. So an electron wave function in a solid treads upon the imaginary as well as future and past domains, linking and coupling all these regions with one another. Information can pass from one of these domains into the other. Is this correct? Something we can't do with our unsymmetric time (due to arrow of time introduced by decoherence).
I have no idea what you are trying to say here, and I agree with Drakkith.

mfb said:
I have no idea what you are trying to say here, and I agree with Drakkith.

Why is it wrong? There are many quantum interpretations. Let's use one where it has ontological aspect, and where the electron wave function can tread into other aspect of existence. Therefore, in solid crystal lattice, an electron wave function become severely smeared and spread out.
But the smearing is not only through space. It's also through the [higher dimensions]. In other words, an electron wave function in a crystal treads upon the imaginary as well as future and past domains, linking and coupling all these regions with one another. Information can pass from one of these domains into the other.

What part of the above is wrong (any or all). Kindly correct which part is
wrong and why. So if it is wrong. Then can find other more exotic processes that can explain reality better.

jake jot said:
What part of the above is wrong (any or all). Kindly correct which part is
wrong and why. So if it is wrong. Then can find other more exotic processes that can explain reality better.

No. We don't do that here. We teach actual science, we don't discuss people's personal interpretations or theories.

jake jot said:
Why is it wrong?
To answer that question you would first have to phrase it more clearly so others can understand what you mean.

Delta2, nasu, Vanadium 50 and 1 other person
mfb said:
To answer that question you would first have to phrase it more clearly so others can understand what you mean.

Let's discuss actual physics.
When we make measurement, we don't really have access to the whole wave function but only the collapsed part, and randomly. So from the point of view of particle physicists, only a tiny information is acquired.

I'd like to understand from the point of view of the electron. Since it is smeared in the solid. And solid is time symmetric. Then it can theoreticaly access the past and future, right?

If wrong, why can't it when electron is smeared wave function and it is time symmetric.

Reference:

https://phys.org/news/2015-07-time-symmetric-quantum-theory-causality-free.html

"The laws of classical mechanics are independent of the direction of time, but whether the same is true in quantum mechanics has been a subject of debate. While it is agreed that the laws that govern isolated quantum systems are time-symmetric, measurement changes the state of a system according to rules that only appear to hold forward in time, and there is difference in opinion about the interpretation of this effect."

After a Mentor discussion, this thread will remain closed. Thanks everybody who tried to help the OP.

## 1. What are energy bands in solid state?

Energy bands in solid state refer to the range of energies that electrons in a solid material can have. These bands are formed by the overlapping of energy levels of individual atoms in the material.

## 2. How are energy bands related to the concept of timelessness?

The concept of timelessness in energy bands refers to the fact that the energy levels of electrons in a solid material do not change over time. This is because the energy bands are a fundamental property of the material and are not affected by external factors such as time.

## 3. What is the significance of energy bands in solid state physics?

Energy bands play a crucial role in understanding the behavior of electrons in solid materials. They determine the electrical and thermal properties of materials and are essential for the functioning of electronic devices.

## 4. Can energy bands in solid state be manipulated?

Yes, energy bands can be manipulated by applying external forces such as an electric field or changing the temperature of the material. This can alter the energy levels of electrons and affect the properties of the material.

## 5. How are energy bands in solid state studied?

Energy bands in solid state are studied using various experimental techniques such as X-ray crystallography, electron spectroscopy, and electrical measurements. Theoretical models and simulations are also used to understand the behavior of energy bands in different materials.

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