Extension of the Standard Model
1 March 2017
In spite of intensive search no deviations from the predictions of the Standard Model of elementary particles have yet been reliably revealed. However, a number of phenomena cannot be explained in the framework of this theory, e.g., the existence of dark matter. G. Ballesteros (the University of Paris-Saclay, France) et al. proposed a simple minimal extension of the Standard Model, called SMASH, that can solve simultaneously a number of problems in elementary particle physics and cosmology. Some elements of this extension have already been developed by M.E. Shaposhnikov, I.I. Tkachev, F.L. Bezrukov and other researchers, and G. Ballesteros with colleagues unified all these elements into a self-consistent model. The proposed extension adds to the particles of the Standard Model three right-handed neutrinos, two Weyl fermions, and a scalar field σ which breaks the Peccei-Quinn symmetry, and its vacuum expectation value 1011 GeV is a new energy scale of the theory. This model reproduces inflation cosmology and baryogenesis in the early Universe. At low energies, the new model reduces to the Standard Model augmented by the seesaw mechanism of neutrino mass generation and by axions with masses of 50-200 µeV. Axions with small momenta can be dark matter particles, and they can be sought in experiments on direct registration. The cosmic background of relativistic axions increases the effective number of the degrees of freedom by Δ Nνeff ≈ 0.03, and this prediction can also be verified by measurements of relic radiation polarization. At high energies, the new theory is valid up to the Planck energy scale. At the same time, the SMASH theory does not give the solution to the hierarchy problem and does not explain dark energy in the Universe.
Source: Phys. Rev. Lett. 118 071802 (2017)
Bell test with star light
1 March 2017
Bell inequality violation was demonstrated in a lot of experiments, which confirmed the absence of “hidden parameters” in quantum mechanics. For the choice of the measurement method quantum random-number generators were used under conditions that the choice and the event of measured particle emission were causally disconnected, i.e., were spacelike separated. The loop-hole of the methods of such experiments “with a delayed choice” was the possibility that in the past the states of the device and of the system measured had been specially prepared. Although such an effect from the past looks unlikely, it is in principle not excluded and can theoretically imitate quantum correlations in Bell inequalities. D. Kaiser (Massachusetts Institute of Technology, USA), A. Zeilinger (the Institute for Quantum Optics and Quantum Information, Austria) and their colleagues carried out an experiment in which the choice of the measurement method was triggered by the light of the stars of our Galaxy. The possibility of using the light of astronomical objects in the Bell test has been discussed since the 1970s, and the given experiment was the first where this idea was realized. A pair of quantum-entangled photons was sent from the source to two laboratories located in other buildings. Small telescopes that received the star light were placed on the roofs of these buildings. According to their frequency, randomly registered star-light photons initiated different measurement methods of photon polarization. The Bell inequality violation in the two experiments was confirmed at 7.31σ and 11.93σ levels. Since the light had been running from stars to the Earth for ≈600 years, the preparation of states, if at all, must have occurred over 600 years before. The use of the light from far galaxies or relic radiation photons may postpone the obtained restriction still farther in time.
Source: Phys. Rev. Lett. 118 060401 (2017)
Optical fiber qubit transmission
1 March 2017
B.P. Williams, R.J. Sadlier, and T.S. Humble, researchers from the Oak Ridge National Laboratory (USA) have demonstrated in their experiment a new method of quantum bit (qubit) transmission through ordinary optical fiber in a hyperentangled (entangled in two degrees of freedom) state. Qubit transmission in a hyperentangled state through a free space was demonstrated in 2007 in the experiment with photons which were quantum entangled in spins and orbital angular momenta. But such photons cannot be transmitted through optical fiber. Instead of orbital angular momentum B.P. Williams, R.J. Sadlier, and T.S. Humble used the entanglement of photons in the time of their emission. This method was proposed theoretically by C. Schuck et al in 2006. The entanglement and the time delay necessary for it were provided using an interferometer. In the experiment, they reached the record coding efficiency for linear optics – 1.665 ± 0.018 classical bits per qubit. In the test experiment, a graphical 3.4kB image was qubit transferred through optical fiber.
Source: Phys. Rev. Lett. 118 050501 (2017)
Overstepping the diffraction limit
1 March 2017
The resolving capacity of telescopes and microscopes, their ability to separate two close objects, for example two stars in a binary system, is limited to Rayleigh’s criterion in case the total signal intensity alone is registered. However, it was known from theoretical works that a higher resolution can be attained using additionally the information on the electromagnetic wave phase. The researchers from the University of Toronto W.-K. Tham, H. Ferretti, and A.M. Steinberg demonstrated this method in their experiment. Two images were represented by two incoherent light beams that received different phases by transmission through a glass plate. Phase registration by means of measurement of Gauss-Hermit quadratures made it possible to establish the presence of two images and thus to surpass the Rayleigh criterion.
Source: Phys. Rev. Lett. 118 070801 (2017)
Intermediate mass black hole in a globular cluster
1 March 2017
Observing pulsars, researchers from Harvard-Smithsonian Center for Astrophysics (USA) and the University of Quinsland (Australia) showed that a black hole of intermediate-mass (between the masses of stellar-origin black holes and supermassive black holes in galactic centers) exists in the center of the globular star cluster 47 Tucanae. The dynamic models imply that pulsar distribution in the cluster depends essentially on the central black hole mass because its gravity suppresses the mass segregation effect (the concentration of more massive stars closer to the cluster center). The observations of the period retardation rate of 23 pulsars yielded the acceleration of their motion in the cluster, and these data allowed determination of the central black hole mass as 2200+1500-800M☉. This black hole does not radiate noticeably in radio-frequency and X-ray bands because of the low gas accretion rate.
Source: Nature 542 203 (2017)
The Extracts from the Internet is a section of Uspekhi Fizicheskih Nauk (Physics Uspekhi) the monthly rewiew journal of the current state of the most topical problems in physics and in associated fields. The presented News is devoted to the fundamental discoveries of physics and astrophysics.
Permanent editor is Yu.N. Eroshenko.
It is compiled from a multitude of Internet sources.