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Redshift and time dilatation of Hawking radiation 
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#1
Dec2911, 11:47 AM

P: 246

Micro black holes should in principle be observable by emitting Hawking radiation. However, as this takes place extremely close to the event horizon, shouldn't one expect then extreme redshifting (z = 1/(1Rs/R)^1/2 1, Rs = Schwarzschildradius, R = Radius of Emission) and time dilatation?
In other words, shouldn't see the far away observer the Hawking radiation almost 'frozen'? How long does it take to reach him in far away coordinates? 


#2
Dec3011, 12:51 PM

Sci Advisor
Thanks
P: 4,160

timmdeeg, It's important to remember that Hawking radiation is fundamentally a quantum process, and therefore one shouldn't try to take a view of it which is purely mechanistic. All one can say is that the vacuum "in" state contains near future null infinity a thermal bath of outwardgoing particles. For example where are the particles created? In the vicinity of the hole. You can't say whether it occurs on the surface or near the surface  it is a global effect. And in fact the predominant wavelength of the created particles is about as large as the hole itself.



#3
Dec3111, 05:04 AM

P: 246

You mentioned the thermal bath. Could you kindly explain, whether there is any physical difference between Unruh radiation and Hawking radiation near the horizon? 


#4
Dec3111, 10:07 AM

Sci Advisor
P: 5,446

Redshift and time dilatation of Hawking radiation
the Hawking radiation is already expressed for an asymptotic observer, so there's no additional redshift



#5
Jan112, 08:02 AM

P: 246

Ok, thanks for clarifying.



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