Topological obstructions to perturbations of pairs of operators

1977 ◽  
pp. 70-77
Author(s):  
Jerome Kaminker ◽  
Claude Schochet
Keyword(s):  
Topological Obstructions

scholarly journals Turán numbers for K s,t -free graphs: Topological obstructions and algebraic constructions

2013 ◽  
Vol 197 (1) ◽  
pp. 199-214 ◽  
Author(s):  
Pavle V. M. Blagojević ◽  
Boris Bukh ◽  
Roman Karasev
Keyword(s):  
Topological Obstructions ◽  
Algebraic Constructions

FIVEBRANE STRUCTURES

2009 ◽  
Vol 21 (10) ◽  
pp. 1197-1240 ◽  
Author(s):  
HISHAM SATI ◽  
URS SCHREIBER ◽  
JIM STASHEFF
Keyword(s):  
String Theory ◽  
Heterotic String ◽  
Target Space ◽  
Type Ii ◽  
Anomaly Cancellation ◽  
Heterotic String Theory ◽  
Dual Version ◽  
String Structure ◽  
Topological Obstructions ◽  
The One

We study the cohomological physics of fivebranes in type II and heterotic string theory. We give an interpretation of the one-loop term in type IIA, which involves the first and second Pontrjagin classes of spacetime, in terms of obstructions to having bundles with certain structure groups. Using a generalization of the Green–Schwarz anomaly cancellation in heterotic string theory which demands the target space to have a String structure, we observe that the "magnetic dual" version of the anomaly cancellation condition can be read as a higher analog of String structure, which we call Fivebrane structure. This involves lifts of orthogonal and unitary structures through higher connected covers which are not just 3- but even 7-connected. We discuss the topological obstructions to the existence of Fivebrane structures. The dual version of the anomaly cancellation points to a relation of string and Fivebrane structures under electric-magnetic duality.

TOPOLOGICAL OBSTRUCTIONS TO BRST INVARIANCE

1993 ◽  
Vol 08 (32) ◽  
pp. 3057-3070
Author(s):  
NIKOLAOS A. BATAKIS ◽  
ALEXANDROS A. KEHAGIAS
Keyword(s):  
Gauge Theory ◽  
Fundamental Representation ◽  
Connected Space ◽  
Generating Functional ◽  
Gauge Groups ◽  
Independent Components ◽  
Covering Group ◽  
The Family ◽  
Topological Obstructions ◽  
Brst Invariance

It is shown that, due to topological obstructions, the effective action of a gauge theory in a multiple-connected space-time containing one fermion n-plet in the fundamental representation of the covering group of the gauge group is not, in general, BRST-invariant. A resolution to this problem is attained with the introduction of identical copies of the original n-plet, one for each of the effectively independent components of the symmetry group, and a truly invariant generating functional is constructed. Examples with explicit gauge groups and their possible relevance to the family problem or to the SU(3) flavors of quarks are briefly discussed.

scholarly journals Topological obstructions for submanifolds in low codimension

2017 ◽  
Vol 196 (1) ◽  
pp. 11-26 ◽  
Author(s):  
Christos-Raent Onti ◽  
Theodoros Vlachos
Keyword(s):  
Topological Obstructions
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