What is the definition of adiabatic CMb spectrum in simple inflationary models?

In summary, The CMb spectrum is considered adiabatic in simple inflationary models, meaning that the density perturbations are the same for all components of the Universe. This concept is often contrasted with isocurvature fluctuations, which have different density perturbations for different components. For more information and references, see the links provided in the conversation.
  • #1
skydivephil
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9
Can someone give a clear definition of what we mean when we say the CMb spectrum is adiabatic and what it means for simple infaltionary models?
 
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  • #3


Thanks for that but I don't see cosmology or CMb research listed as one of those concepts.
 
  • #4


It is usually used in the context of the density perturbations. In particular the density perturbations will be the same for all constituent components of the Universe:

[tex] \frac{\delta \rho_a}{(\rho_a + \bar{\rho})} [/tex] will be the same for all components (enumerated by 'a') where [tex]\bar{\rho}[/tex] is our mean background value. Have a quick glance at the http://en.wikipedia.org/wiki/Primordial_fluctuations" [Broken] page.
 
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Thanks
 
  • #6


The alternatives to adiabatic are usually along the lines of 'isocurvature' fluctuations etc. Just in case you were interested here are a few interesting links:

http://arxiv.org/abs/astro-ph/9610219" [Broken]

http://arxiv.org/abs/0907.0261" [Broken]

http://arxiv.org/abs/0803.0547" [Broken] (This has a clearer discussion than the 7yr or 3yr papers in my opinion. ; It's also well referenced so you can seek out other papers of interest etc.)

http://arxiv.org/abs/0812.3500" [Broken]
 
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1. What is a CMb spectrum?

A CMb spectrum, also known as a cosmic microwave background spectrum, is a measurement of the intensity of radiation emitted by the universe at specific wavelengths. This radiation is the leftover heat from the Big Bang and is a key piece of evidence for the theory of the origin of the universe.

2. What does it mean for a CMb spectrum to be adiabatic?

An adiabatic CMb spectrum means that the distribution of matter and energy in the universe is uniform. This is an important characteristic as it supports the idea that the universe has been expanding at a constant rate since the Big Bang.

3. How is the adiabatic nature of the CMb spectrum measured?

The adiabatic nature of the CMb spectrum is measured through various experiments, such as the Cosmic Background Explorer (COBE) and the Planck satellite mission. These experiments collect data on the intensity and distribution of radiation in the universe, allowing scientists to determine if the spectrum is adiabatic or not.

4. What implications does an adiabatic CMb spectrum have on our understanding of the universe?

An adiabatic CMb spectrum supports the idea of an expanding universe, as well as the concept of the Big Bang theory. It also provides evidence for the uniformity and consistency of the universe, as the adiabatic nature of the spectrum suggests that the distribution of matter and energy has remained relatively constant since the beginning of the universe.

5. Are there any competing theories to explain the adiabatic nature of the CMb spectrum?

Currently, there are no widely accepted competing theories to explain the adiabatic nature of the CMb spectrum. However, some theories, such as the Steady State theory, propose alternative explanations for the evolution of the universe that do not align with the adiabatic nature of the CMb spectrum.

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