Negative Temperature: Exploring Entropy & Kinetic Energy

In summary, the conversation discusses the concept of negative temperature, where entropy decreases as energy increases, and raises questions about its possibility without crossing absolute zero, its relationship to kinetic energy, and its potential for creating more than 100% efficient engines. It is suggested to do a forum search or check the Wikipedia article for further information.
  • #1
tannerbk
41
0
I've read recently about systems with the ability to reach negative temperature: where entropy decreases as energy increases. I have a couple question regarding this. First, how is it possible to reach negative temperature without crossing absolute zero? Is there some discontinuity like a phase transition that allows this to happen? How can negative temperature be related to the kinetic energy of system?

Additionally, wouldn't this allow heat to flow from negative to positive temperature, leading to more than 100% efficient engines?

Finally, could this have anything to do with negative pressure associated with positive vacuum energy density?
 
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  • #2
Do a forum search. This has been discussed here not too long back.
 
  • #3
I tried before I posted this, can you provide a link?
 
  • #4
DO A SEARCH --- use "negative temperature" in quotes
 
  • #5
phinds said:
DO A SEARCH --- use "negative temperature" in quotes

Use the "Search PF via Google" option at the SEARCH pulldown menu at the top of the page. Then click the thread hit from 3-Jan-2013.

:smile:
 
  • #6
berkeman said:
Use the "Search PF via Google" option at the SEARCH pulldown menu at the top of the page. Then click the thread hit from 3-Jan-2013.

:smile:

Thanks!
 
  • #7

1. What is negative temperature?

Negative temperature is a concept in thermodynamics that describes a state in which a system has a higher energy at a lower temperature than it does at a higher temperature. This may seem counterintuitive, as we typically associate higher energy with higher temperatures, but it is possible in certain systems due to the laws of thermodynamics.

2. How is negative temperature related to entropy?

Negative temperature is closely related to entropy, which is a measure of the disorder or randomness in a system. Entropy and temperature have an inverse relationship, meaning that as temperature increases, entropy typically also increases. In systems with negative temperature, the increase in entropy with temperature reverses, leading to counterintuitive behavior.

3. What is the difference between negative and positive temperature?

The main difference between negative and positive temperature is the direction of energy flow. In a system with positive temperature, energy flows from hotter objects to colder objects, while in a system with negative temperature, energy flows from colder objects to hotter objects. Negative temperature systems also have a maximum energy state, while positive temperature systems have a minimum energy state.

4. Can negative temperature be achieved in real-world systems?

Yes, negative temperature can be achieved in certain real-world systems, such as atomic and molecular systems. However, these systems are typically very small and require precise control and manipulation to achieve negative temperature states. Negative temperature can also be simulated in certain computer models and simulations.

5. What are some potential applications of negative temperature?

Some potential applications of negative temperature include creating ultra-cold systems for studying quantum mechanics and exploring new states of matter. Negative temperature can also be used in information processing and computing, as well as in the development of new materials with unique properties.

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