Pedro Jimenez-Delgado, Jefferson Lab.
Extractions of polarized and unpolarized parton distributions functions
Seminar room, Kenkyu honkan 3F
The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed at the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic Scattering will be presented. In the second part of the talk the ongoing update of the JR unpolarized parton distributions will be reported. Different aspects or polarized and unpolarized global QCD analysis will be discussed, including effects due to the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions
Kenta Hotokezaka, Kyoto University
Mass ejection of compact binary merger and the progenitor model of GRB 130603B
Seminar Room, Kenkyu Honkan 3F A transient powered by the radioactive decay of r-process elements the so-called kilonova is one of the possible observational consequences of compact binary mergers including at least one neutron star. Recent observations discover a kilonova associated with the short GRB130603B.
A transient powered by the radioactive decay of r-process elements the so-called kilonova is one of the possible observational consequences of compact binary mergers including at least one neutron star. Recent observations discover a kilonova associated with the short GRB130603B.
We explore the possible progenitor of this event based on numerical-relativity simulations and radiative transfer simulations for the dynamical ejecta of binary neutron star (NS-NS) mergers and black hole – neutron star binary (BH-NS) mergers. We show that the only soft EOS models could produce the observed luminosity for the NS-NS ejecta. Our results also show that a BH-NS model is more favorable for GRB130603B than a NS-NS model.
Kentaroh Yoshida, Kyoto University
Holographic description of Schwinger effect
Meeting room 1, Kenkyu honkan 1F
The Schwinger effect is known as a non-perturbative phenomenon in quantum electromagnetic dynamics (QED). The virtual electron-positron pairs can be created as real particles due to the presence of a strong electric field. Recently, Semenoff and Zarembo have proposed a setup to consider the Schwinger effect in the context of the AdS/CFT correspondence. In this talk, after a review of the setup, I will explain a generalization to include magnetic field. I also give another support for the proposal of Semenoff and Zarembo from the viewpoint of quark-antiquark potentials. This talk is based on the collaboration with Yoshiki Sato (Dept. of Phys., Kyoto Univ.) arXiv:1303.0112, 1304.7917.
Holger F. Hofmann, Hiroshima University
Complex probabilities as fundamental law of physics : What weak measurement statistics tell us about the nature of reality
Seminar room, Kenkyu honkan 3F According to quantum mechanics, the measurement of a property A necessarily disturbs the system, so that the value of a different property B obtained after the measurement of A is different from the value of B before the measurement of A. However, it is possible to decrease the measurement interaction to the point where the disturbance of B is negligible. In this weak measurement limit, it is possible to determine the value of A conditioned by the final measurement outcome of B, without disturbing B in the process. The weak values obtained in such measurements have attracted a lot of attention because they can exceed the limits set by the extremal eigenvalues of A [1]. Recently, it has been shown that weak values can be described as averages of complex valued probability distributions, where the possibility of negative real parts not only explains the observation of averages outside the range of eigenvalues, but also resolves a number of quantum paradoxes, which are usually based on the assumption of positive joint probabilities [2].
According to quantum mechanics, the measurement of a property A necessarily disturbs the system, so that the value of a different property B obtained after the measurement of A is different from the value of B before the measurement of A. However, it is possible to decrease the measurement interaction to the point where the disturbance of B is negligible. In this weak measurement limit, it is possible to determine the value of A conditioned by the final measurement outcome of B, without disturbing B in the process. The weak values obtained in such measurements have attracted a lot of attention because they can exceed the limits set by the extremal eigenvalues of A [1]. Recently, it has been shown that weak values can be described as averages of complex valued probability distributions, where the possibility of negative real parts not only explains the observation of averages outside the range of eigenvalues, but also resolves a number of quantum paradoxes, which are usually based on the assumption of positive joint probabilities [2].
In this presentation, I show that complex conditional probabilities provide a consistent explanation of all quantum effects. In particular, it is pointed out that complex conditional probabilities describe universal relations between three physical properties that represent the correct quantum limit of classical determinism. In these relations, the complex phase corresponds to the action of transformations between two physical properties along the third. Importantly, a simultaneous assignment of realities to the three different properties is impossible, because measurement interactions change the effective reality of the system according to the laws of dynamics. This relation between complex probabilities and measurement dynamics can be summarized by a quantitative relation which I call the law of quantum ergodicity. As I recently showed, this law can be used to derive the complete Hilbert space formalism, providing a physical explanation of quantum mechanics in terms of the fundamental relation between the reality of physical properties and the dynamics by which they are observed [3]. The results recently obtained from weak measurements of quantum systems might thus be the key that unlocks the mysteries of quantum mechanics.
[1] Aharonov et al., PRL 60, 1351 (1988)
[2] Hofmann, NJP 14, 043031 (2012)
[3] Hofmann, arXiv:1306.2993
Hiroyuki Kamano, RCNP, Osaka Univ.
Dynamical coupled-channels approach to light-flavor baryon
Meeting room 1, Kenkyu honkan 1F An understanding of the mass spectrum and structure of the excited nucleons (N*) is a fundamental challenge in the hadron physics. So far, a number of static hadron models such as quark models have been developed to study the N* spectrum and form factors. In such static models the excited states are usually treated as stable particles, and thus the resulting mass spectrum has real values. However, in reality the N* states couple strongly to the meson-baryon continuum states and can exist only as unstable resonances in the pi N and gamma N reactions. Dynamical effects caused by such strong couplings to the continuum states affect significantly the N* properties and cannot be neglected in extracting the N* resonance parameters (pole mass, residues etc) from the data and giving physical interpretations to those parameters. It is thus well recognized nowadays that properly incorporating such dynamical effects are indispensable to the theoretical studies of the N* spectroscopy.
An understanding of the mass spectrum and structure of the excited nucleons (N*) is a fundamental challenge in the hadron physics. So far, a number of static hadron models such as quark models have been developed to study the N* spectrum and form factors. In such static models the excited states are usually treated as stable particles, and thus the resulting mass spectrum has real values. However, in reality the N* states couple strongly to the meson-baryon continuum states and can exist only as unstable resonances in the pi N and gamma N reactions. Dynamical effects caused by such strong couplings to the continuum states affect significantly the N* properties and cannot be neglected in extracting the N* resonance parameters (pole mass, residues etc) from the data and giving physical interpretations to those parameters. It is thus well recognized nowadays that properly incorporating such dynamical effects are indispensable to the theoretical studies of the N* spectroscopy.
In this situation, we have been exploring the nature of the N* states as unstable resonances through the comprehensive analysis of the world data of pion-, photon-, and electron-induced meson production reactions off a nucleon. The analysis is performed with a reaction model based on the ANL-Osaka Dynamical Coupled-Channels (DCC) approach. The model satisfies the multichannel unitarity of the S-matrix in the channel-space spanned by the pi N, eta N, pi pi N, rho N, pi Delta, sigma N, K Lambda, and K Sigma channels, and successfully treats the reaction dynamics constrained by the unitarity.
In this talk, I will overview our effort on the extraction of nucleon resonances based on the ANL-Osaka DCC approach, particularly focusing on presenting our recent results of the N* resonance extraction through the fully combined analysis of pion- and photon-induced pi N, eta N, K Lambda, and K Sigma production reactions. I will also present a prospect of our future direction.
Shuta Tanaka, ICRR, the University of Tokyo
Study of pulsar wind properties: the pair multiplicity problem and induced Compton scattering off radio pulses
Meeting room 1, Kenkyu Honkan 1F
A pulsar wind is a cold relativistic electron-positron outflow originating from a pulsar magnetosphere. Because pulsar winds are radiatively inefficient, it is difficult to obtain their properties, such as the magnetization, the bulk Lorentz factor and the pair multiplicity which corresponds to the number of the particles. In my talk, I introduce the pair multiplicity problem which is independent from the well-known problem of the magnetization called sigma-problem. We study induced Compton scattering off radio pulses by the pulsar wind to constrain pulsar wind properties by imposing that radio pulses are not scattered by the wind. We find that the pair multiplicity of the Crab pulsar can be more than two orders of magnitude larger than the previously inferred value only when the magnetization of the Crab pulsar wind is close to unity at the light cylinder.
Eduardo Martin-Martinez, Institute For Quantum Computing, University of Waterloo
Detectors for probing relativistic quantum physics beyond perturbation theory
Seminar room, Kenkyu Honkan 3F We develop a general formalism for a non-perturbative treatment of harmonic-oscillator particle detectors in relativistic quantum field theory using continuous-variables techniques. By means of this we forgo perturbation theory altogether and reduce the complete dynamics to a readily solvable set of first-order, linear differential equations. The formalism applies unchanged to a wide variety of physical setups, including arbitrary detector trajectories, any number of detectors, arbitrary time-dependent quadratic couplings, arbitrary Gaussian initial states, and a variety of background spacetimes. As a first set of concrete results, we prove non-perturbatively–and without invoking Bogoliubov transformations–that an accelerated detector in a cavity evolves to a state that is very nearly thermal with a temperature proportional to its acceleration, allowing us to discuss the universality of the Unruh effect. Additionally we quantitatively analyze the problems of considering single-mode approximations in cavity field theory and show the emergence of causal behaviour when we include a sufficiently large number of field modes in the analysis. Finally, we analyze how the harmonic particle detector can harvest entanglement from the vacuum. We also study the effect of noise in time dependent problems introduced by suddenly switching on the interaction versus ramping it up slowly (adiabatic activation).
We develop a general formalism for a non-perturbative treatment of harmonic-oscillator particle detectors in relativistic quantum field theory using continuous-variables techniques. By means of this we forgo perturbation theory altogether and reduce the complete dynamics to a readily solvable set of first-order, linear differential equations. The formalism applies unchanged to a wide variety of physical setups, including arbitrary detector trajectories, any number of detectors, arbitrary time-dependent quadratic couplings, arbitrary Gaussian initial states, and a variety of background spacetimes. As a first set of concrete results, we prove non-perturbatively–and without invoking Bogoliubov transformations–that an accelerated detector in a cavity evolves to a state that is very nearly thermal with a temperature proportional to its acceleration, allowing us to discuss the universality of the Unruh effect. Additionally we quantitatively analyze the problems of considering single-mode approximations in cavity field theory and show the emergence of causal behaviour when we include a sufficiently large number of field modes in the analysis. Finally, we analyze how the harmonic particle detector can harvest entanglement from the vacuum. We also study the effect of noise in time dependent problems introduced by suddenly switching on the interaction versus ramping it up slowly (adiabatic activation).
Ref. Phys. Rev. D 87, 084062 (2013)
Go Mishima, The University of Tokyo
Precision Measurements as a Probe of Hidden Photon
Meeting Room 1, Kenkyu Honkan 1F
An extra Abelian gauge group arises naturally in a variety of extensions of the standard model. If the extra gauge boson, hidden photon, satisfies some conditions, then it can solve the muon g-2 anomaly, a persistent discrepancy between measured value and the standard model prediction of the anomalous magnetic moment of the muon. We investigate constraints on the hidden photon from precision measurements like electron g-2 and hydrogen spectroscopy, and show that the hidden photon which solves the muon g-2 anomaly can be examined by a experiment planed to start in the near future.
Yoshihisa Kitazawa, KEK
Soft gravitons screen couplings in de Sitter space
Meeting Room 1, Kenkyu Honkan 1F
We investigate the effect of the soft gravitons on the microscopic matter dynamics in de Sitter space. Scale invariance of the soft graviton propagator is the source of the de Sitter symmetry breaking. We find quartic, Yukawa and gauge couplings become time dependent and diminish with time. In a simple model, the cosmological constant is self-tuned to vanish due to UV-IR mixing effect. We also discuss phenomenological implications such as SUSY breaking.
佐々木寿彦, Photon Science Center, University of Tokyo
重力波観測における標準量子限界について
Seminar room, Kenkyu honkan 3F
