scholarly journals On the twistor space of the six-sphere

1989 ◽  
Vol 39 (1) ◽  
pp. 119-127 ◽  
Author(s):  
Emilio Musso
Keyword(s):  
Twistor Space ◽  
Einstein Metric ◽  
Dirac Spinor ◽  
Kähler Structure ◽  
Spinor Bundle ◽  
Complex Quadric ◽  
Relevant Group ◽  
Complex Lines ◽  
The Right ◽  
Twistor Fibration

The set of all complex lines of the right-handed Dirac spinor bundle of a standard six-sphere is the total space of the twistor fibration. The twistor space, endowed with its natural Kähler structure, is recognised to be a six-dimensional complex quadric. The relevant group is Spin(7), which acts transitively on the six-quadric, as a group of fiber-preserving isometries. We use a result due to Berard-Bérgery and Matsuzawa to show the existence of a non-Kähler, non symmetric, Hermitian-Einstein metric on the six-quadric, which is Spin(7)-invariant.

scholarly journals SPIN-3/2 FERMIONS IN TWISTOR FORMALISM

2001 ◽  
Vol 16 (32) ◽  
pp. 2103-2113 ◽  
Author(s):  
MITSUO J. HAYASHI
Keyword(s):  
Twistor Space ◽  
Integrability Condition ◽  
Local Existence ◽  
Flat Space ◽  
Space Time ◽  
Necessary Condition ◽  
Field Equations ◽  
Weyl Spinor ◽  
Cartan Theory ◽  
The Right

Consistency conditions for the local existence of massless spin-3/2 fields have been explored to find the facts that the field equations for massless helicity-3/2 particles are consistent if the space–time is Ricci-flat, and that in Minkowski space–time the space of conserved charges for the fields is its twistor space itself. After considering the twistorial methods to study such massless helicity-3/2 fields, we show in flat space–time that the charges of spin-3/2 fields, defined topologically by the first Chern number of their spin-lowered self-dual Maxwell fields, are given by their twistor space, and in curved space–time that the (anti-)self-duality of the space–time is the necessary condition. Since in N=1 supergravity torsions are the essential ingredients, we generalize our space–time to that with torsion (Einstein–Cartan theory), and investigate the consistency of existence of spin-3/2 fields in this theory. A simple solution to this consistency problem is found: The space–time has to be conformally (anti-)self-dual, left-(or right-) torsion-free. The integrability condition on α-surface shows that the (anti-)self-dual Weyl spinor can be described only by the covariant derivative of the right-(left-)handed torsion.

The Twistor Space of a 3-Sasakian Manifold

1997 ◽  
Vol 08 (01) ◽  
pp. 31-60 ◽  
Author(s):  
Charles P. Boyer ◽  
Krzysztof Galicki
Keyword(s):  
Scalar Curvature ◽  
Smooth Manifold ◽  
Twistor Space ◽  
Sasakian Manifold ◽  
Positive Scalar Curvature ◽  
Einstein Metric ◽  
Singular Case ◽  
Positive Scalar ◽  
Smooth Case ◽  
Quaternionic Kähler

Any compact 3-Sasakian manifold [Formula: see text] is a principal circle V-bundle over a compact complex orbifold [Formula: see text]. This orbifold has a contact Fano structure with a Kähler–Einstein metric of positive scalar curvature and it is the twistor space of a positive compact quaternionic Kähler orbifold [Formula: see text]. We show that many results known to hold when [Formula: see text] is a smooth manifold extend to this more general singular case. However, we construct infinite families of examples with [Formula: see text] which sharply differs from the smooth case, where there is only one such [Formula: see text].

Freedom, Participation and Corporations: The Issue of Corporate (Economic) Democracy

1992 ◽  
Vol 2 (3) ◽  
pp. 251-269 ◽  
Author(s):  
George G. Brenkert
Keyword(s):  
Social Contract ◽  
State Government ◽  
Economic Democracy ◽  
Corporate Decisions ◽  
Relevant Group ◽  
Right To Participation ◽  
Large Corporations ◽  
The Right

The freedom (or its lack) of employees within large corporations has been the topic of considerable attention. Various discussions have invoked utilitarian appeals, social contract arguments, rights to meaningful jobs and analogies between corporations and state government. After briefly reviewing and rejecting these approaches, this paper contends that the legitimate exercise of corporate authority requires its accountability to a relevant group. It is then argued that the most relevant group are the employees over whom such power is exercised and that the form such accountability must take is that of recognizing the right of employees to participate in corporate decisions and actions. Recognition of this right to participation, it is contended, constitutes respect for the freedom of corporate employees.

scholarly journals FANO MANIFOLDS, CONTACT STRUCTURES, AND QUATERNIONIC GEOMETRY

1995 ◽  
Vol 06 (03) ◽  
pp. 419-437 ◽  
Author(s):  
CLAUDE LEBRUN
Keyword(s):  
Riemannian Manifold ◽  
Scalar Curvature ◽  
Contact Structure ◽  
Twistor Space ◽  
Positive Scalar Curvature ◽  
Einstein Metric ◽  
Contact Structures ◽  
Fano Manifolds ◽  
Quaternionic Geometry ◽  
Structure Formula

Let Z be a compact complex (2n+1)-manifold which carries a complex contact structure, meaning a codimension-1 holomorphic sub-bundle D⊂TZ which is maximally non-integrable. If Z admits a Kähler-Einstein metric of positive scalar curvature, we show that it is the Salamon twistor space of a quaternion-Kähler manifold (M4n, g). If Z also admits a second complex contact structure [Formula: see text], then Z=CP2n+1. As an application, we give several new characterizations of the Riemannian manifold HPn= Sp(n+1)/(Sp(n)×Sp(1)).

The Kähler structure of asymptotic twistor space

1977 ◽  
Vol 18 (1) ◽  
pp. 58-64 ◽  
Author(s):  
M. Ko ◽  
E. T. Newman ◽  
R. Penrose
Keyword(s):  
Twistor Space ◽  
Kähler Structure

Investor-State Dispute Settlement under NAFTA Chapter 11: The Shape of Things to Come?

1998 ◽  
Vol 35 ◽  
pp. 263-290
Author(s):  
J. Anthony VanDuzer
Keyword(s):  
Free Trade Agreement ◽  
Dispute Settlement ◽  
Trade Agreement ◽  
Minimum Standards ◽  
The North ◽  
State Behaviour ◽  
Nafta Chapter 11 ◽  
To Come ◽  
The Right

SummaryRecently, there has been a proliferation of international agreements imposing minimum standards on states in respect of their treatment of foreign investors and allowing investors to initiate dispute settlement proceedings where a state violates these standards. Of greatest significance to Canada is Chapter 11 of the North American Free Trade Agreement, which provides both standards for state behaviour and the right to initiate binding arbitration. Since 1996, four cases have been brought under Chapter 11. This note describes the Chapter 11 process and suggests some of the issues that may arise as it is increasingly resorted to by investors.

What face familiarity feelings say about the lateralization of specific entities within the core system

2019 ◽  
Vol 42 ◽  
Author(s):  
Guido Gainotti
Keyword(s):  
Temporal Lobe ◽  
Memory System ◽  
Core System ◽  
The Core ◽  
Memory Traces ◽  
Specific Memory ◽  
Target Article ◽  
Temporal Structures ◽  
The Right

Abstract The target article carefully describes the memory system, centered on the temporal lobe that builds specific memory traces. It does not, however, mention the laterality effects that exist within this system. This commentary briefly surveys evidence showing that clear asymmetries exist within the temporal lobe structures subserving the core system and that the right temporal structures mainly underpin face familiarity feelings.

Study of charge transfer in FeTi

1983 ◽  
Vol 41 ◽  
pp. 296-297
Author(s):  
J. Taft∅
Keyword(s):  
Charge Transfer ◽  
Charge Distribution ◽  
Electron Scattering ◽  
Periodic System ◽  
Electron Distribution ◽  
Scattering Amplitude ◽  
Transition Elements ◽  
Hartree Fock ◽  
Cscl Structure ◽  
The Right

It is well known that for reflections corresponding to large interplanar spacings (i.e., sin θ/λ small), the electron scattering amplitude, f, is sensitive to the ionicity and to the charge distribution around the atoms. We have used this in order to obtain information about the charge distribution in FeTi, which is a candidate for storage of hydrogen. Our goal is to study the changes in electron distribution in the presence of hydrogen, and also the ionicity of hydrogen in metals, but so far our study has been limited to pure FeTi. FeTi has the CsCl structure and thus Fe and Ti scatter with a phase difference of π into the 100-ref lections. Because Fe (Z = 26) is higher in the periodic system than Ti (Z = 22), an immediate “guess” would be that Fe has a larger scattering amplitude than Ti. However, relativistic Hartree-Fock calculations show that the opposite is the case for the 100-reflection. An explanation for this may be sought in the stronger localization of the d-electrons of the first row transition elements when moving to the right in the periodic table. The tabulated difference between fTi (100) and ffe (100) is small, however, and based on the values of the scattering amplitude for isolated atoms, the kinematical intensity of the 100-reflection is only 5.10-4 of the intensity of the 200-reflection.

New Dimensions in Freeze-Etching

1969 ◽  
Vol 27 ◽  
pp. 202-203 ◽  
Author(s):  
Russell L. Steere ◽  
Michael Moseley
Keyword(s):  
Fracture Surfaces ◽  
Aluminum Specimen ◽  
Specimen Holder ◽  
Freeze Etching ◽  
The Right

A redesigned specimen holder and cap have made possible the freeze-etching of both fracture surfaces of a frozen fractured specimen. In principal, the procedure involves freezing a specimen between two specimen holders (as shown in A, Fig. 1, and the left side of Fig. 2). The aluminum specimen holders and brass cap are constructed so that the upper specimen holder can be forced loose, turned over, and pressed down firmly against the specimen stage to a position represented by B, Fig. 1, and the right side of Fig. 2.

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