Hubble sphere - Revision history

Cosmo All at 09:38, 23 April 2014

2014-04-23T09:38:39Z

2014-04-23T09:38:21Z

2014-04-23T09:36:49Z

2014-02-04T10:40:00Z

2014-02-04T00:50:10Z

‎Problem 7

2014-02-04T00:21:49Z

2014-01-28T12:08:37Z

Created page with "6"

New page

[[Category:Horizons|6]]

← Older revision		Revision as of 09:38, 23 April 2014
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−
−	~~<references>~~
−	~~<ref name=qwerty>~~
−	~~<div id="qwerty"></div>~~
−	~~=== Problem 13 ===~~
−	~~Show that if $q$ is not constant, comoving bodies can be inside and outside of the Hubble sphere at different times. But not so for the observable universe; once inside, always inside.~~
−	~~<div class="NavFrame collapsed">~~
−	~~<div class="NavHead">solution</div>~~
−	~~<div style="width:100%;" class="NavContent">~~
−	<p style="text-align: left;">From (\ref{dRHdt}) we see that recession velocity of the Hubble sphere can be lesser or greater than $c$, depending on the sign of $q$. As recession velocity of matter on it is exactly $c$, be definition, this means that matter can cross the Hubble sphere in both directions at different times.
−
−	"Horizons are like membranes; the photon horizon acts as a two-way membrane (comoving bodies can cross in both directions depending on the value of $q$), and the particle horizon acts like a one-way membrane (comoving bodies always move in and never out)." E. Harrison, Science of the Universe.</p>
−	~~</div>~~
−	~~</div>~~
−	~~</ref>~~
−	~~</references>~~

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← Older revision		Revision as of 09:36, 23 April 2014
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	</div>		</div>
	</div>		</div>
		+
		+
		+	<references>
		+	<ref name=qwerty>
		+	<div id="qwerty"></div>
		+	=== Problem 13 ===
		+	Show that if $q$ is not constant, comoving bodies can be inside and outside of the Hubble sphere at different times. But not so for the observable universe; once inside, always inside.
		+	<div class="NavFrame collapsed">
		+	<div class="NavHead">solution</div>
		+	<div style="width:100%;" class="NavContent">
		+	<p style="text-align: left;">From (\ref{dRHdt}) we see that recession velocity of the Hubble sphere can be lesser or greater than $c$, depending on the sign of $q$. As recession velocity of matter on it is exactly $c$, be definition, this means that matter can cross the Hubble sphere in both directions at different times.
		+
		+	"Horizons are like membranes; the photon horizon acts as a two-way membrane (comoving bodies can cross in both directions depending on the value of $q$), and the particle horizon acts like a one-way membrane (comoving bodies always move in and never out)." E. Harrison, Science of the Universe.</p>
		+	</div>
		+	</div>
		+	</ref>
		+
		+	on the problem <ref name=qwerty/>
		+
		+
		+	</references>

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      <p style="text-align: left;">From (\ref{dRHdt}) we see that recession velocity of the Hubble sphere can be lesser or greater than $c$, depending on the sign of $q$. As recession velocity of matter on it is exactly $c$, be definition, this means that matter can cross the Hubble sphere in both directions at different times.
-``Horizons are like membranes; the photon horizon acts as a two-way membrane (comoving bodies can cross in both directions depending on the value of $q$), and the particle horizon acts like a one-way membrane (comoving bodies always move in and never out).'' E.~Harrison, Science of the Universe.</p>
+"Horizons are like membranes; the photon horizon acts as a two-way membrane (comoving bodies can cross in both directions depending on the value of $q$), and the particle horizon acts like a one-way membrane (comoving bodies always move in and never out)." E. Harrison, Science of the Universe.</p>
 </div>
 </div>

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 q=-\frac{\ddot{a}/a}{H^{2}}
 \end{equation}
- is the deceleration parameter.
+is the deceleration parameter.
 <div class="NavFrame collapsed">
    <div class="NavHead">solution</div>
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 === Problem 8 ===
 Show that