Agullo, I., Navarro-Salas, J., Olmo, G. J., & Parker, L. (2010). Hawking Radiation by Kerr Black Holes and Conformal Symmetry. Phys. Rev. Lett., 105(21), 211305–4pp.
Abstract: The exponential blueshift associated with the event horizon of a black hole makes conformal symmetry play a fundamental role in accounting for its thermal properties. Using a derivation based on two-point functions, we show that the full spectrum of thermal radiation of scalar particles by Kerr black holes can be explicitly derived on the basis of a conformal symmetry arising in the wave equation near the horizon. The simplicity of our approach emphasizes the depth of the connection between conformal symmetry and black hole radiance.
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Gessner, M., & Smerzi, A. (2023). Hierarchies of Frequentist Bounds for Quantum Metrology: From Cramer-Rao to Barankin. Phys. Rev. Lett., 130(26), 260801–6pp.
Abstract: We derive lower bounds on the variance of estimators in quantum metrology by choosing test observables that define constraints on the unbiasedness of the estimator. The quantum bounds are obtained by analytical optimization over all possible quantum measurements and estimators that satisfy the given constraints. We obtain hierarchies of increasingly tight bounds that include the quantum Cramer-Rao bound at the lowest order. In the opposite limit, the quantum Barankin bound is the variance of the locally best unbiased estimator in quantum metrology. Our results reveal generalizations of the quantum Fisher information that are able to avoid regularity conditions and identify threshold behavior in quantum measurements with mixed states, caused by finite data.
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Zanon, I. et al, Domingo-Pardo, C., & Gadea, A. (2023). High-Precision Spectroscopy of O-20 Benchmarking Ab Initio Calculations in Light Nuclei. Phys. Rev. Lett., 131(26), 262501–7pp.
Abstract: The excited states of unstable O-20 were investigated via.-ray spectroscopy following the O-19(d, p)O-20 reaction at 8 AMeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2(2)(+) and 3(1)(+) states were firmly established. From the gamma-ray branching and E2/M1 mixing ratios for transitions deexciting the 2(2)(+) and 3(1)(+) states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of gamma-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.
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Grodner, E. et al, Gadea, A., Algora, A., Agramunt, J., Domingo-Pardo, C., Molina, F., et al. (2014). Hindered Gamow-Teller Decay to the Odd-Odd N = Z Ga-62: Absence of Proton-Neutron T=0 Condensate in A=62. Phys. Rev. Lett., 113(9), 092501–5pp.
Abstract: Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T = 1, J(pi) = 0(+) ground state of Ge-62 into excited states of the odd-odd N = Z nucleus Ga-62. The experiment is performed at GSI Helmholtzzentrum fur Shwerionenforshung with the Ge-62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T-1/2 = 2 82.9(14) ms is measured for the Ge-62 ground state. Six excited states of Ga-62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical predictions of the interacting shell model and the quasiparticle random phase approximation. The absence of any sizable low-lying Gamow-Teller strength in the reported beta-decay experiment supports the hypothesis of a negligible role of coherent T = 0 proton-neutron correlations in Ga-62.
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Blanton, T. D., Romero-Lopez, F., & Sharpe, S. R. (2020). I=3 Three-Pion Scattering Amplitude from Lattice QCD. Phys. Rev. Lett., 124(3), 032001–7pp.
Abstract: We analyze the spectrum of two- and three-pion states of maximal isospin obtained recently for isosymmetric QCD with pion mass M approximate to 200 MeV in Horz and Hanlon, [Phys. Rev. Lett. 123, 142002 (2019)]. Using the relativistic three-particle quantization condition, we find similar to 2 sigma evidence for a nonzero value for the contact part of the 3 pi(+) (I = 3) scattering amplitude. We also compare our results to leading-order chiral perturbation theory. We find good agreement at threshold and some tension in the energy dependent part of the 3 pi(+) scattering amplitude. We also find that the 2 pi(+) (I = 2) spectrum is fit well by an s-wave phase shift that incorporates the expected Adler zero.
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