P M S Blackett, G Occhialini and the invention of the counter-controlled cloud chamber (1931–32)

Leone, Matteo; Robotti, Nadia

doi:10.1088/0143-0807/29/2/001

Cited by 9 publications

(9 citation statements)

References 25 publications

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“…(12) and (13) defining v k and p k , Eqs. (49) and (50) do not mix different modes. Making use of Eqs.…”

Section: A Quantum Information Theory and Cosmological Perturbationsmentioning

confidence: 98%

“…In an analogy with Eqs. (49) and (50), let us therefore introduce the quantitiesq 1,2 andπ 1,2 defined byq 1,2 = ( √ 2k) −1 (a 1,2 +a † 1,2 ) andπ 1,2 = −i k/2(a 1,2 −a † 1,2 ). This defines the vectorP j = (k 1/2q 1 , k −1/2π 1 , k 1/2q 2 , k 1/2π 2 ) which is the equivalent ofR j defined after Eq.…”

Section: Appendix B: Quantum Discord For a General Splitting Of The Smentioning

confidence: 99%

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Quantum discord of cosmic inflation: Can we show that CMB anisotropies are of quantum-mechanical origin?

2016

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We investigate the quantumness of primordial cosmological fluctuations and its detectability. The quantum discord of inflationary perturbations is calculated for an arbitrary splitting of the system, and shown to be very large on super-Hubble scales. This entails the presence of large quantum correlations, due to the entangled production of particles with opposite momentums during inflation. To determine how this is reflected at the observational level, we study whether quantum correlators can be reproduced by a non-discordant state, i.e. a state with vanishing discord that contains classical correlations only. We demonstrate that this can be done for the power spectrum, the price to pay being twofold: first, large errors in other two-point correlation functions and second, the presence of intrinsic non-Gaussianity. The detectability of these two features remains to be determined but could possibly rule out a non-discordant description of the cosmic microwave background. If one abandons the idea that perturbations should be modeled by quantum mechanics and wants to use a classical stochastic formalism instead, we show that any two-point correlators on super-Hubble scales can be exactly reproduced regardless of the squeezing of the system. The latter becomes important only for higher order correlation functions that can be accurately reproduced only in the strong squeezing regime.

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“…(12) and (13) defining v k and p k , Eqs. (49) and (50) do not mix different modes. Making use of Eqs.…”

Section: A Quantum Information Theory and Cosmological Perturbationsmentioning

confidence: 98%

Section: Appendix B: Quantum Discord For a General Splitting Of The Smentioning

confidence: 99%

Quantum discord of cosmic inflation: Can we show that CMB anisotropies are of quantum-mechanical origin?

2016

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“…Also, these perturbed equations, along with the Friedmann equation and the equation of motion for φ 0 in the slow-roll approximation, i.e. 3Hφ ′ 0 + a 2 ∂ φ V ≈ 0, imply that (see for instance Appendix A of [49]):…”

Section: Inflation In the Semiclassical Picturementioning

confidence: 99%

“…In the case of inflation in a quaside Sitter background, this last condition together with (12) correspond to fix B k = 0 and |A k | = π 4k . Readers interested in how the quasi-de Sitter case is analyzed within collapse schemes, when the BD vacuum is chosen as the initial condition (and where the prediction for the scalar spectral index is n s = 1), are invited to see the work [49].…”

Section: Quantum Perturbations Vacuum Choice and Collapse Hypotmentioning

confidence: 99%

Novel vacuum conditions in inflationary collapse models

Bengochea

León

2017

Physics Letters B

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Within the framework of inflationary models that incorporate a spontaneous reduction of the wave function for the emergence of the seeds of cosmic structure, we study the effects on the primordial scalar power spectrum by choosing a novel initial quantum state that characterizes the perturbations of the inflaton. Specifically, we investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities when the standard Bunch-Davies vacuum is replaced by another one that minimizes the renormalized stress-energy tensor via a Hadamard procedure. We think that this new prescription for selecting the vacuum state is better suited for the self-induced collapse proposal than the traditional one in the semiclassical gravity picture. We show that the parametrization for the time of collapse, considered in previous works, is maintained. Also, we obtain an angular spectrum for the CMB temperature anisotropies consistent with the one that best fits the observational data. Therefore, we conclude that the collapse mechanism might be of a more fundamental character than previously suspected.Comment: 17 pages, 2 figures. Extended and revised version. To appear in Physics Letters

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“…A few months after Anderson's observation, the existence of the positron in cosmic radiation was fully confirmed by Patrick Blackett and Giuseppe Occhialini at the Cavendish Laboratory in Cambridge. By means of their recently developed counter-controlled cloud chamber [31]a device of greater efficiency than the standard automatic cloud chamber (80% versus 2%) where the coincidence discharge in two Geiger-Müller counters placed above and below the cloud chamber triggered the expansion apparatus of the chamber-the Cavendish researchers succeeded in collecting many photographs showing positron tracks. Sometimes these positrons were detected as electron-positron pairs and sometimes as electron-positron groups, i.e.…”

Section: Towards the Pair Productionmentioning

confidence: 99%

Frédéric Joliot, Irène Curie and the early history of the positron (1932–33)

Leone

Robotti

2010

Eur. J. Phys.

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As is well known, the positron was discovered in August 1932 by Carl Anderson while studying cloud chamber tracks left by cosmic rays. Far less known is the fact that a few months before Anderson's discovery, in April 1932, Frédéric Joliot and Irène Curie had missed an opportunity to discover the positron during a nuclear physics experiment. One year later, in April 1933, the French researchers eventually succeeded in discovering the mechanism of positron-electron pair production. The complex relationship between Anderson's discovery of the positron, Joliot and Curie's missed discovery, and their following work on the pair production is discussed here in detail.

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P M S Blackett, G Occhialini and the invention of the counter-controlled cloud chamber (1931–32)

Cited by 9 publications

References 25 publications

Quantum discord of cosmic inflation: Can we show that CMB anisotropies are of quantum-mechanical origin?

Quantum discord of cosmic inflation: Can we show that CMB anisotropies are of quantum-mechanical origin?

Novel vacuum conditions in inflationary collapse models

Frédéric Joliot, Irène Curie and the early history of the positron (1932–33)

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