scholarly journals ON THE SPIN CORRELATIONS OF MUONS AND TAU LEPTONS GENERATED IN THE ANNIHILATION PROCESSES e+e- → μ+μ-, e+e- → τ+τ-

2014 ◽  
Vol 35 ◽  
pp. 1460452
Author(s):  
VALERY V. LYUBOSHITZ ◽  
VLADIMIR L. LYUBOSHITZ
Keyword(s):  
Angular Correlation ◽  
Tau Leptons ◽  
Triplet States ◽  
Strongly Correlated ◽  
Electromagnetic Process ◽  
Correlation Tensor ◽  
Spin Correlations ◽  
Helicity Amplitudes ◽  
Unpolarized Electron ◽  
The One

Using the technique of helicity amplitudes, the electromagnetic process e+e- → μ+μ-(τ+τ-) is theoretically studied in the one-photon approximation. The structure of the triplet states of the final (μ+μ-) system is analyzed. It is shown that in the case of unpolarized electron and positron the final muons are also unpolarized, but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the (μ+μ-) system are derived. The formula for the angular correlation at the decays of final muons μ+ and μ- is obtained. It is demonstrated that spin correlations of muons in the considered process have the purely quantum character, since one of the Bell-type incoherence inequalities for the correlation tensor components is always violated.

SPIN CORRELATIONS OF THE FINAL LEPTONS IN THE TWO-PHOTON PROCESSES γγ → e+e-, μ+μ-, τ+τ-

2014 ◽  
Vol 35 ◽  
pp. 1460453
Author(s):  
VALERY V. LYUBOSHITZ ◽  
VLADIMIR L. LYUBOSHITZ
Keyword(s):  
Spin Structure ◽  
Triplet States ◽  
Strongly Correlated ◽  
Correlation Tensor ◽  
Spin Correlations ◽  
Two Photon ◽  
Final Electron ◽  
Singlet And Triplet States ◽  
Explicit Expressions

The spin structure of the process γγ → e+e- is theoretically investigated. It is shown that, if the primary photons are unpolarized, the final electron and positron are unpolarized as well but their spins are strongly correlated. For the final (e+e-) system, explicit expressions for the components of the correlation tensor are derived, and the relative fractions of singlet and triplet states are found. It is demonstrated that in the process γγ → e+e- one of the Bell-type incoherence inequalities for the correlation tensor components is always violated and, thus, spin correlations of the electron and positron in this process have the strongly pronounced quantum character. Analogous consideration can be wholly applied as well to the two-photon processes γγ → μ+μ- and γγ → τ+τ-, which become possible at considerably higher energies.

HELICITY AMPLITUDES FOR COLLIDING BEAM SCATTERING OF TWO SPIN 1/2 PARTICLES

1993 ◽  
Vol 08 (30) ◽  
pp. 5383-5407
Author(s):  
T.B. ANDERS ◽  
A.O. BARUT ◽  
W. JACHMANN
Keyword(s):  
Center Of Mass ◽  
Mass System ◽  
Intermediate Transformation ◽  
Beam System ◽  
Pair Annihilation ◽  
Helicity Amplitudes ◽  
Reaction Channels ◽  
Invariant Coupling ◽  
Exchange Scattering ◽  
The One

As a generalization and extension of the extensive tables of polarization asymmetries given in a previous work,1 we present here tables of helicity amplitudes for the scattering of two spin 1/2 particles in the colliding beam system (i.e. two incoming particles with opposite directions but not necessarily of equal momenta). The particles belonging to the same current may have different masses in order to describe particle excitations. The amplitudes are given for six different basic couplings connecting two vector vertices, a vector vertex at the one current and a derivative vector vertex at the other current, two derivative vector vertices, two tensor vertices, and two scalar vertices. The vertices include axial couplings by factors of type 1+cγ5. The amplitudes are written as expressions with 16 components in the six different reaction channels, namely the scattering of two fermions, of two antifermions, and of a fermion and an antifermion, the pair creation by pair annihilation, as well as the exchange scattering for two identical fermions or antifermions. The formulas may be used for an analysis which extracts the invariant coupling functions from the experimental data obtained in the colliding beam system directly without an intermediate transformation to the center of mass system.

scholarly journals Risk Aversion and Social Networks

2014 ◽  
Vol 13 (2) ◽  
Author(s):  
Jaromír Kovářík ◽  
Marco J. van der Leij
Keyword(s):  
Risk Aversion ◽  
Undergraduate Students ◽  
Network Structure ◽  
Network Formation ◽  
Empirical Finding ◽  
Local Network ◽  
Network Clustering ◽  
Strongly Correlated ◽  
Social Network Structure ◽  
The One

AbstractThis paper first investigates empirically the relationship between risk aversion and social network structure in a large group of undergraduate students. We find that risk aversion is strongly correlated to local network clustering, that is, the probability that one has a social tie to friends of friends. We then propose a network formation model that generates this empirical finding, suggesting that locally superior information on benefits makes it more attractive for risk averse individuals to link to friends of friends. Finally, we discuss implications of this model. The model generates a positive correlation between local network clustering and benefits, even if benefits are distributed independently ex ante. This provides an alternative explanation of this relationship to the one given by the social capital literature. We also establish a linkage between the uncertainty of the environment and the network structure: risky environments generate more clustered and more unequal networks in terms of connectivity.

scholarly journals A novel method of ESR oscillating magnetization value determination in strongly correlated metals

2018 ◽  
Vol 185 ◽  
pp. 02003 ◽  
Author(s):  
Marat Gilmanov ◽  
Alexey Semeno ◽  
Alexander Samarin ◽  
Sergey Demishev
Keyword(s):  
Resonance Field ◽  
Simple Expression ◽  
60 Ghz ◽  
Strongly Correlated ◽  
Static Magnetization ◽  
Spin Resonance ◽  
Order Of Magnitude ◽  
Novel Method ◽  
Value Determination ◽  
The One

We propose a powerful method of direct measurement of oscillating magnetization by the electron spin resonance, based on dependence of resonant conditions on geometry of the experiment. Theoretical consideration of the matter leads to a simple expression for oscillating magnetization. Approbation of this method is implemented by means of cavity ESR spectrometer (60 GHz) on two diverse metallic systems, where static magnetization at the resonance field varies by an order of magnitude. Quantitative values of oscillating magnetization (905 G for EuB6 at T = 4.2 K and 94 G for CeB6 at T = 1.8 K) are in appropriate agreement with the one obtained by the other methods.

Weight gain and faecal nitrogen excretion in grazing British and Zebu crossbred steers

1963 ◽  
Vol 14 (6) ◽  
pp. 898 ◽  
Author(s):  
GC Ashton
Keyword(s):  
Weight Gain ◽  
Nitrogen Excretion ◽  
Strongly Correlated ◽  
Average Gain ◽  
Breed Differences ◽  
Faecal Nitrogen ◽  
The One

The excretion of faecal nitrogen by 16 grazing steers, eight Hereford x Shorthorn and eight Zebu crossbreds, was determined at intervals over a period of 11 months. It was found that the non-dialysable faecal nitrogen fraction was the one most strongly correlated with gain. Statistically this fraction accounted for 68% of the variation in average gain of the two breed groups between measurement intervals, and for 75% of the variation in weight gain between individual steers during the summer gain period. The data gave no indication of inherent breed differences in intake, as judged by non-dialysable nitrogen excretion.

scholarly journals FERTILITY AND SOCIAL SECURITY

2015 ◽  
Vol 81 (3) ◽  
pp. 261-299 ◽  
Author(s):  
Michele Boldrin ◽  
Mariacristina De Nardi ◽  
Larry E. Jones
Keyword(s):  
Social Security ◽  
Old Age ◽  
Cross Section ◽  
Developed Countries ◽  
The Other ◽  
Strongly Correlated ◽  
Jones Model ◽  
Key Factor ◽  
Broad Cross Section ◽  
The One

Abstract:The data show that an increase in government provided old-age pensions is strongly correlated with a reduction in fertility. What type of model is consistent with this finding? We explore this question using two models of fertility, the one by Barro and Becker (1989), and the one inspired by Caldwell and developed by Boldrin and Jones (2002). In the Barro and Becker model parents have children because they perceive their children’s lives as a continuation of their own. In the Boldrin and Jones’ framework parents procreate because the children care about their old parents’ utility, and thus provide them with old age transfers. The effect of increases in government provided pensions on fertility in the Barro and Becker model is very small, and inconsistent with the empirical findings. The effect on fertility in the Boldrin and Jones model is sizeable and accounts for between 55 and 65% of the observed Europe–US fertility differences both across countries and across time and over 80% of the observed variation seen in a broad cross section of countries. Another key factor affecting fertility the Boldrin and Jones model is the access to capital markets, which can account for the other half of the observed change in fertility in developed countries over the last 70 years.

Self-Consistent Hole Motion and Spin Excitations in A Quantum Antiferromagnet

1989 ◽  
Vol 03 (12) ◽  
pp. 1913-1932 ◽  
Author(s):  
Z.B. Su ◽  
Y.M. Li ◽  
W.Y. Lai ◽  
L. Yu
Keyword(s):  
The Self ◽  
Spin Excitation ◽  
Spin Correlations ◽  
Local Distortion ◽  
Spin Excitations ◽  
Self Consistent ◽  
The Stability ◽  
The One ◽  
Quantum Antiferromagnet ◽  
Self Consistency

A new quantum Bogoliubov-de Gennes (BdeG) formalism is developed to study the self-consistent motion of holes and spin excitations in a quantum antiferromagnet within the generalized t-J model. On the one hand, the effects of local distortion of spin configurations and the renormalization of the hole motion due to virtual excitations of the distorted spin background are treated on an equal footing to obtain the hole wave function and its spectrum, as well as the effective mass for a propagating hole. On the other hand, the change of the spin excitation spectrum and the spin correlations due to the presence of dynamical holes are studied within the same adiabatic approximation. The stability of the hole states with respect to such changes justifies the self-consistency of the proposed formalism.

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