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Related Concept Videos

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
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Spin–Spin Coupling: One-Bond Coupling01:17

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Related Experiment Video

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Setting Limits on Supersymmetry Using Simplified Models
07:46

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Published on: November 15, 2013

Nonperturbative yukawa couplings from string instantons.

Ralph Blumenhagen1, Mirjam Cvetic, Dieter Lüst

  • 1Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany.

Physical Review Letters
|March 21, 2008
PubMed
Summary
This summary is machine-generated.

Nonperturbative D-brane instantons generate crucial couplings absent in perturbative string theory. This mechanism explains specific Yukawa couplings and generates mass terms for exotic matter fields, aiding their decoupling.

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Area of Science:

  • String Theory and Particle Physics
  • Quantum Field Theory and Phenomenology

Background:

  • Perturbative string theory often misses certain couplings relevant to particle physics phenomenology.
  • D-brane instantons offer a nonperturbative approach to uncover these missing interactions in compactified string theories.

Purpose of the Study:

  • To investigate the generation of perturbatively absent Yukawa couplings using nonperturbative D-brane instantons.
  • To explore the creation of mass terms for matter fields in intersecting D6-brane models.
  • To present a mechanism for the decoupling of exotic matter particles.

Main Methods:

  • Analysis of nonperturbative D-brane instanton effects in type II orientifold compactifications.
  • Calculation of the SU(5) GUT Yukawa coupling of type <10 10 5(H)>.
  • Study of a globally consistent intersecting D6-brane model.

Main Results:

  • Demonstrated the generation of the perturbatively vanishing SU(5) GUT Yukawa coupling.
  • Showed the generation of mass terms for matter fields within the D6-brane model.
  • Identified a potential mechanism for exotic matter decoupling.

Conclusions:

  • Nonperturbative D-brane instantons are essential for generating phenomenologically relevant couplings.
  • The discussed mechanism provides a pathway for understanding exotic matter behavior in string theory models.