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Questions tagged [unruh-effect]

This tag is for questions regarding to the Unruh effect (also known as the Fulling–Davies–Unruh effect), the hypothetical prediction that an accelerating observer will observe a thermal bath, like blackbody radiation, whereas an inertial observer would observe none. It was described by Stephen Fulling in 1973, Paul Davies in 1975, and William Unruh in 1976.

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Static Patch Decomposition of Bunch Davies Vacuum

In the Jerusalem Lectures on Black Holes section 3.3 the author considers a QFT in Minkowski space. He then picks out a space coordiante, say $x$, and divides the Hilbert space $H$ of the QFT in two ...
Aralian's user avatar
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Is there an analogous Unruh effect for observers on a rigidly rotating ring?

I read up on the Unruh effect recently and what I got from it is that its basically a result of transforming to Rindler coordinates and using a Bogoliubov transformation to change the creation and ...
Aravind Karthigeyan's user avatar
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GZK Limit in the Far Future and interaction with Vacuum energy?

The GZK limit stops high energy protons from propagating long distances because of the interaction with the CMB. But as the universe ages the CMB will become more red shifted. Will this mean the the ...
EraserDriver's user avatar
2 votes
1 answer
51 views

What if acceleration changes in the Unruh effect?

Based on the Unruh effect, when a observer accelerates then he will see a thermal bath. mathematically the vacuum state for a non-inertial observer is $$|0\rangle=\text{cos}^{-1}(r)\sum_{n=0}^{\infty}\...
reza's user avatar
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How to relate the two expressions of thermal spectrum?

I am reading a proof of the fact that if there exists a monochromatic plane electromagnetic wave for an observer in frame $S$, an observer in a frame $S'$, which is uniformly accelerated with respect ...
Singh's user avatar
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Accelerating frame of reference, fermions and probability conservation

I'm looking at solutions to the massless Dirac equation in an accelerating frame of reference in $(1+1)$-dimensions but the wave functions I get appear to violate probability conservation. My ...
Kris's user avatar
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1 answer
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Unruh Radiation from hovering?

I know that masses on their own don't produce Unruh radiation outside of black holes which produce a similar effect known as Hawking radiation. However, what if some observer hovers above the Earth ...
Roghan Arun's user avatar
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1 answer
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Don't all objects that collapse have an apparent event horizon and so Hawking radiates?

So say there is an object that is in the form of gas and dust and a core that weighs 10 earths is in the center and there is a sphere of gas around it that weighs 50 Earths, so the final mass is only ...
Roghan Arun's user avatar
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1 vote
0 answers
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Behavior of Rindler modes for massless scalar field in 3+1 dimensions

Thank you in advance for any answer to my question. I'm having trouble understanding the behaviour of the mode functions of a massless Klein-Gordon field in Rindler coordinates. We are in 3+1 ...
luta_naccarata's user avatar
1 vote
1 answer
60 views

Cosmological horizon and Hawking/Unruh radiation? [closed]

I have two questions about cosmological horizons and their emission of radiation The first one is: There are some authors that propose that dark energy or the accelerated expansion of the universe ...
vengaq's user avatar
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2 answers
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Why is Unruh radiation in a full 4$\pi$ solid angle contrary to Hawking's radiation?

I have some trouble asking this question, so I will try a roundabout approach to explain what I mean. If (outside of Earth atmosphere) one looks at the sun from different distances, the light coming ...
Alfred's user avatar
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2 votes
1 answer
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Can we infer Hawking radiation assuming the Unruh effect?

An observer near the event horizon of a black hole will experience an extremely strong gravitational field. Due to the principle of equivalence, this observer cannot locally distinguish between this ...
VVM's user avatar
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1 answer
140 views

Are non-virtual particles of QFT real?

Perhaps the question may seem a bit provocative, but it refers to several mathematical and, presently physical facts, pointed out a long time ago: The Unruh effect suggests that an accelerated ...
Davius's user avatar
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14 votes
2 answers
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What are the experimental difficulties in measuring the Unruh effect?

The Unruh effect was predicted in 1976. As someone with no background in experimental physics I find it surprising this effect hasn't been measured yet. What are the experimental difficulties (and ...
More Anonymous's user avatar
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1 answer
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Fulling–Davies–Unruh effect with non-uniform acceleration

Can there be some version of the Fulling–Davies–Unruh effect, in which the accelerating observer is moving with a non-uniform acceleration? Can someone refer some papers to read? If there can not be ...
schris38's user avatar
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Will gravitational waves decay into photons? (and by how much?)

We know intense regions of curvature, for example near a black hole horizon, induce a flow of electromagnetic waves (and, less so, other particles). aka Hawking radiation. By contrast, curvature in ...
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4 votes
1 answer
710 views

Boulware and Unruh vacuum in Schwarzschild spacetime

I am studying quantization in Schwarzschild spacetime. In class the Boulware vacuum $\left| B \right>$ has been defined using the o.n. modes $u_I(x) = \frac{1}{4\pi \sqrt{\omega}}e^{-i\omega v}$, $...
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Does accelerating blackhole grow in size due to constant infalling unruh radiation?

Unruh effects stipulates that an accelerating observer will observe a thermal bath, like blackbody radiation, whereas an inertial observer would observe none. Now assume a constantly accelerating ...
Eye-In-Styn's user avatar
3 votes
1 answer
223 views

Path Integral for Unruh Effect

In derivation of Unruh effect, according to arxiv 2108.09188, we have $$ \langle\phi_L|\exp(-\pi H)|\phi_R\rangle=\int_{\phi=\phi_R}^{\phi=\phi_L} D\phi e^{-S_E}\propto \int_{lower\space half\space ...
gshxd's user avatar
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How does Unruh detector work?

It is often said that an inertial observer in flat spacetime vacuum will see an accelerating observer thermalize (Unruh Effect). If an accelerated observer takes a particle in a box coupled with the ...
user avatar
3 votes
1 answer
108 views

Is it possible to explain radiation of an accelerated charged particle via the Unruh effect?

From the point view of a noninertial observer, if a charged particle accelerates then it can catch the Unruh particle and excite. After that, the charged particle emits it and falls back to its ground ...
reza's user avatar
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1 answer
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Role of horizon in Unruh effect

I’m reading this on the Unruh effect and it is derived by calculating the Bogoliubov coefficients between the Minkowski and Rindler observer. Rindler observers use a different set of modes to describe ...
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3 votes
1 answer
112 views

Why is the Unruh effect observer dependent?

Why Unruh radition is observer dependent why Hawking radition is not observer dependent? I know hawking radiation is caused by the creation of a pair partice and antiparticle in two different sides ...
reza's user avatar
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1 answer
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Bogoliubov coefficients between inertial frames

The Klein–Gordon Equation in Minkowski space says $\partial_\mu \partial^\mu \phi+ m^2 \phi = 0$. The solution has modes $e^{ikx}$, $e^{-ikx}$ scaled by creation and annihilation operators $a^{\dagger}...
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1k views

How is Hawking radiation formally derived?

[EDITED] I'm a postdoc working in cond-mat/quant theory, and I've heard some explanations of Hawking radiation that strike me as inconsistent or silly (e.g., in terms of pair production). I'm hoping ...
just a phase's user avatar
4 votes
1 answer
521 views

Does String Theory predict things like Unruh effect and Hawking radiation?

I've seen the other post about this, but the answer only discusses Unruh effect rather than String theory. Hawking radiation and Unruh effect solidify fields as the universe's fundamental objects. ...
Ryder Rude's user avatar
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1 answer
157 views

Does the Unruh effect assume its conclusion?

Unruh effect says that accelerating observers see the single particle states of inertial frames as thermal baths. But it proves it by defining the particle states in the accelerating observer's frame ...
Ryder Rude's user avatar
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6 votes
1 answer
859 views

Might the tiny Hawking radiation from our cosmic event horizon (CEH) be additive, since my CEH is not your CEH?

Concerning our cosmic event horizon, an interesting question arises from the seemingly innocent statement, "My cosmic event horizon is not your cosmic event horizon." Ie: Since 'you' and 'I'...
user86742's user avatar
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2 votes
0 answers
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Informal derivation of the Unruh temperature

Imagine a charged particle of mass $m$ at rest in the electromagnetic vacuum. The particle interacts most strongly with zero-point modes that have a wavelength $\lambda_C$ similar to the Compton ...
John Eastmond's user avatar
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1 answer
163 views

Unruh effect origin of particle

I have a little confusion about where from the particle are coming in Unruh effect. Vacuum fluctuation is always there and does not depend on whether the frame/detector is moving or not. Vacuum ...
Tanmoy Pati's user avatar
1 vote
1 answer
87 views

Calculation of expectation of number of particle using Bogolubov transformation [closed]

we have two bases connected by Bogoljubov transformations. In the first basis, creation and annihilation operators are ($a,a^\dagger$) and in the second basis ($a',a'^\dagger$). They are connected by \...
Tanmoy Pati's user avatar
0 votes
1 answer
67 views

Proof probability distribution of number of particles seen in different basis connected by Bogoljubov transformation is Poissonian

Let we have two bases connected by Bogoljubov transformations. In the first basis, creation and annihilation operators are ($a,a^\dagger$) and in the second basis ($a',a'^\dagger$). They are connected ...
Tanmoy Pati's user avatar
1 vote
0 answers
23 views

Significance of non-zero cross energy-momentum tensor in Fulling Davies Unruh effect

In the Fulling Davies Unruh effect We can get the outgoing particle flux from the asymptotic future region $\mathscr{I}^+$ from the mirror trajectory as the following $$ \mathcal{F}=\int_0^\infty \...
Tanmoy Pati's user avatar
0 votes
0 answers
56 views

An example of the vacuum emitting photons?

Imagine we have two parallel wires with a potential difference of $V$ volts that form the opposite sides of a square of size $\lambda$. Any virtual electron-positron pairs that form between the wires ...
John Eastmond's user avatar
11 votes
1 answer
2k views

Does an electric field cause the vacuum to emit photons?

As I understand it electron-positron pairs pop in and out of the vacuum on a time scale $T$ inversely proportional to the electron mass. Imagine we put a static electric field across the vacuum. ...
John Eastmond's user avatar
2 votes
0 answers
141 views

Deriving Hawking temperature "from" Unruh effect and their relation

Let me recall some basic computational facts (the meaning of which I am trying to understand). In flat space, an adapted coordinate $(\tau, \xi)$ associated with an observer with constant proper ...
Lelouch's user avatar
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1 vote
2 answers
128 views

Do the null geodesics of photons emitted by Hawking radiation arise from the event horizon?

It is a well-known explanation of Hawking radiation that it originates from the quantum fluctuations near the horizon. Does it mean that one can look at the photons (part of the radiation) and follow ...
Lelouch's user avatar
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4 votes
0 answers
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Carroll's derivation of Hawking radiation

In Carroll's Spacetime and Geometry: An Introduction to General Relativity, in his derivation of Hawking radiation Carroll makes the following statement: "as observed over length and timescales ...
user6314's user avatar
3 votes
0 answers
57 views

Lowering the Schwinger limit with superconductors while considering the Unruh effect?

Unruh Effect is often left out in calculations regarding the Schwinger limit. I've been looking at different mechanisms for more easily attaining the Schwinger limit. So far, the only thing I have ...
Jarod's user avatar
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2 votes
0 answers
156 views

Rindler decomposition using Euclidean path integral

In section 3.3 of Jerusalem Lectures on Black Holes and Quantum Information (arXiv:1409.1231), Daniel Harlow wants to calculate the following Euclidean path integral $$\langle\phi |\Omega\rangle\...
K. Sreeman Reddy's user avatar
4 votes
1 answer
455 views

How to derive the Unruh effect (or the thermofield double state) from the path integral?

I have been reading about the path integral approach to deriving the thermofield double state for the Minkowski vacuum in terms of the Rindler states: \begin{equation} \left|0_{M}(t=0)\right\rangle=\...
Kris's user avatar
  • 841
3 votes
1 answer
151 views

Questions about the Unruh effect derivation in Wald's QFT in curved spacetime

So I'm currently reading chapter 5 of Wald's book on QFT in curved spacetime and I'm terribly confused with the notation in the last steps of his Unruh effect derivation. Context: In eq. 5.1.26, he ...
Rafael Mancini's user avatar
1 vote
2 answers
153 views

Is the experimental evidence confirming black hole entropy or Unruh radiation?

The question says it all: how does Bekenstein–Hawking entropy or radiation fare when compared with observation? Or maybe just the idea of Unruh radiation?
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1 vote
1 answer
719 views

In the Unruh effect, where does the energy of the particles come from?

If you accelerate an object with constant acceleration, you will in effect create a black hole in the opposite direction in which you are traveling. This being due to light rays at a certain distance ...
user avatar
4 votes
1 answer
172 views

Does the count of particles depend on the observer?

The Lagrangian and Action, say in QED, is invariant to Lorentz boosts and independent of observers. (It’s possible to convert from a Lagrangian to the Hamiltonian view via a Legendre transform $H=vp-L$...
nemui's user avatar
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0 votes
0 answers
271 views

Physical significance of number operator in QFT

Does the expectation value of the number operator corresponds to any physical observable or has any significance in classical limit? This is probably a dumb question, but I'm struggling to identify ...
paul230_x's user avatar
  • 1,752
3 votes
1 answer
107 views

Why Unruh temperature is the temperature measured by observer with $\xi = 0$?

My coordinate transformation is: \begin{align} t=\frac{1}{a} e^{a \xi} \sinh (a \eta), \quad x=\frac{1}{a} e^{a \xi} \cosh (a \eta). \end{align} The free scalar field is quantized under this ...
CondensedGravity's user avatar
4 votes
1 answer
412 views

Doubts about the "periodicity trick" to compute temperature

The "periodicity trick" is a mysterious way to compute some sort of temperature associated to a Rindler-like spacetime. Suppose there exist coords $R\in(0,\infty), \eta\in(-\infty,\infty)$ ...
nodumbquestions's user avatar
4 votes
1 answer
674 views

Hawking Temperature for a Given Metric

I want to calculate the Hawking temperature of the metric $$\mathrm ds^{2}=-\left(1-\frac{r^{2}}{l^{2}}\right)\mathrm dt^{2}\ +\frac{\mathrm dr^{2}}{\left(1-\frac{r^{2}}{l^{2}}\right)}+\ r^{2}\mathrm ...
Star21's user avatar
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2 votes
1 answer
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Davies & Unruh: vacuum temperature is proportional to acceleration. But $T$ is not a vector

Davies and Unruh showed that vacuum temperature is given by acceleration: $$T = \frac{\hbar a}{2 \pi k_\mathrm B c}.$$ But acceleration is a vector, temperature is not. If vacuum temperature produces ...
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