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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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
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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 ...
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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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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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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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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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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 ...
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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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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 $u_I(x) = \frac{1}{4\pi \sqrt{\omega}}e^{-i\omega v}$, $...
lucabtz's user avatar
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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
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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 ...
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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 ...
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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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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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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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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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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
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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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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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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'...
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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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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
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1 answer
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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
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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
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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
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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
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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
135 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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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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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
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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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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\...
Kasi Reddy Sreeman Reddy's user avatar
4 votes
1 answer
337 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
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1 answer
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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
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2 answers
142 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
589 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
148 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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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 ...
KP99's user avatar
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2 votes
1 answer
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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
340 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
561 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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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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What is the physical interpretation of negative Unruh temperature?

Actually the Unruh temperature is vectorial since it is proportional to acceleration but derived for only one space dimension so at least positive and negative. What can negative Unruh temperature ...
David Jonsson's user avatar
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1 answer
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Unruh effect derivation

I was going through the derivation of the Unruh effect in chapter 5 of these lecture notes ("Lecture Series on Relativistic Quantum Information" by Prof Ivette Fuentes). On p.26 the author ...
Kouta Dagnino's user avatar
16 votes
2 answers
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Can Quantum Field Theory not handle accelerated frames of reference?

Since Quantum Field Theory can't handle gravity, and gravity is mathematically equivalent to acceleration (equivalence principle), does this mean Quantum Field theory can't handle accelerated frames ...
Egg Man's user avatar
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Does Unruh radiation potentially explain the Paradox of 'apparent non-radiation of charged particles in a gravitational field'?

The Wikipedia entry on 'Paradox of radiation of charged particles in a gravitational field' does not mention Unruh or Hawking radiation, but I don't see why they wouldn't provide a solution.... ...
Kurt Hikes's user avatar
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Does the Unruh effect need the accelerating observer's Hilbert space to be smaller than the inertial one?

I've encounter two different approaches to the Unruh effect and I feel like they are not consistent with one another. Bogoliubov Transformation In this approach the basic statement is that the vacuum ...
P. C. Spaniel's user avatar
2 votes
2 answers
238 views

Firewall in Rindler horizon

In arXiv:1409.1231 in section 3.5 above equation (3.34) Daniel Harlow says More precisely if the left and right wedges are completely uncorrelated, as in the state 3.33, then the typical difference ...
Kasi Reddy Sreeman Reddy's user avatar
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1 answer
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Usage of Rindler coordinates in studying Unruh Effect

When studying the Unruh Effect, Rindler coordinates are being used for the observer with constant acceleration. I am confused as to why Rindler coordinates are used as I do not see the motivation for ...
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3 votes
1 answer
262 views

How can Unruh radiation ever be real?

It is speculated that Unruh radiation exists for accelerating observers in flat spacetime. A thermometer in the frame will point at a higher value than for someone in a stationary frame. In the ...
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