Neutrino Zero Modes and Stability of Electroweak Strings

We discuss massless and massive neutrino zero modes in the background of an electroweak string. We argue that the eventual absence of the neutrino zero mode implies the existence of topologically stable strings where the required non-trivial topology has been induced by the fermionic sector.Comment: 6 pages, 2 figures, Presented at DPF 2000: The Meeting of the Division of Particles and Fields of the American Physical Society, Columbus, Ohio, 9-12 Aug 2000. Proceedings to be published in International Journal of Modern Physics

Can primordial magnetic fields seeded by electroweak strings cause an alignment of quasar axes on cosmological scales?

The decay of non-topological electroweak strings formed during the electroweak phase transition in the early universe may leave an observable imprint in the universe today. Such strings can naturally seed primordial magnetic fields. Protogalaxies then tend to form with their axis of rotation parallel to the external magnetic field, and moreover, the external magnetic field produces torque which forces the galaxy axis to align with the magnetic field, even if the two axis were not aligned initially. This can explain an (observed, but as of yet unexplained) alignment of the quasars' polarization vectors. We demonstrate that the shape of a magnetic field left over from two looped electroweak strings can explain the non-trivial alignment of quasar polarization vectors and make predictions for future observations.Comment: 9 pages, 8 figures, figure altered for clarification, accepted for publication in Phys. Rev. Le

Volume Renormalization and the Higgs

Traditionally, Quantum Field Theory (QFT) treats particle excitations as point-like objects, which is the source of ubiquitous divergences. We demonstrate that a minimal modification of QFT with finite volume particles may cure QFT of divergences and illuminate the physics behind the mathematical construct of our theories. The method allows for a non-perturbative treatment of the free field and self-interacting theories (though extensions to all interacting field theories might be possible). In particular, non-perturbatively defined mass is finite. When applied to the standard model Higgs mechanism, the method implies that a finite range of parameters allows for creation of a well defined Higgs particle, whose Compton wavelength is larger than its physical size, in the broken symmetry phase (as small oscillations around the vacuum). This has profound consequences for Higgs production at the LHC. The parameter range in which the Higgs excitation with the mass of 125 GeV behaves as a proper particle is very restricted.Comment: Published in Europhysics Letters, Volume 105, Issue 1, article id. 11002 (2014

Implications of the Higgs discovery for gravity and cosmology

The discovery of the Higgs boson is one of the greatest discoveries in this century. The standard model is finally complete. Apart from its significance in particle physics, this discovery has profound implications for gravity and cosmology in particular. Many perturbative quantum gravity interactions involving scalars are not suppressed by powers of Planck mass. Since gravity couples anything with mass to anything with mass, then Higgs must be strongly coupled to any other fundamental scalar in nature, even if the gauge couplings are absent in the original Lagrangian. Since the LHC data indicate that the Higgs is very much standard model-like, there is very little room for non-standard model processes, e.g. invisible decays. This severely complicates any model that involves light enough scalar that the Higgs can kinematically decay to. Most notably, these are the quintessence models, models including light axions, and light scalar dark matter models.Comment: Essay written for the Gravity Research Foundation 2013 Awards for Essays on Gravitation. Honorable mention. Accepted for publicatio

Inconsistencies in Verlinde's emergent gravity

We point out that recent Verlinde's proposal of emergent gravity suffers from some internal inconsistencies. The main idea in this proposal is to preserve general relativity at short scales where numerous tests verified its validity, but modify it on large scales where we meet puzzles raised by observations (in particular dark matter), by using some entropic concepts. We first point out that gravity as a conservative force is very difficult (if possible at all) to portray as an entropic force. We then show that the derivation of the MOND relation using the elastic strain idea is not self-consistent. When properly done, Verlinde's elaborate procedure recovers the standard Newtonian gravity instead of MOND.Comment: accepted for publication in JHE