37,914 research outputs found
Gauge Coupling Unification in E6 F-Theory GUTs with Matter and Bulk Exotics from Flux Breaking
We consider gauge coupling unification in E6 F-Theory Grand Unified Theories
(GUTs) where E6 is broken to the Standard Model (SM) gauge group using fluxes.
In such models there are two types of exotics that can affect gauge coupling
unification, namely matter exotics from the matter curves in the 27 dimensional
representation of E6 and the bulk exotics from the adjoint 78 dimensional
representation of E6. We explore the conditions required for either the
complete or partial removal of bulk exotics from the low energy spectrum. In
the latter case we shall show that (miraculously) gauge coupling unification
may be possible even if there are bulk exotics at the TeV scale. Indeed in some
cases it is necessary for bulk exotics to survive to the TeV scale in order to
cancel the effects coming from other TeV scale matter exotics which would by
themselves spoil gauge coupling unification. The combination of matter and bulk
exotics in these cases can lead to precise gauge coupling unification which
would not be possible with either type of exotics considered by themselves. The
combination of matter and bulk exotics at the TeV scale represents a unique and
striking signature of E6 F-theory GUTs that can be tested at the LHC.Comment: 21 pages, 5 figure
Involutions and the Gelfand character
The Gelfand representation of is the multiplicity-free direct
sum of the irreducible representations of . In this paper, we
use a result of Adin, Postnikov, and Roichman to find a recursive generating
function for the Gelfand character. In order to find this generating function,
we investigate descents of so-called -unimodal involutions
Proof of Luck: an Efficient Blockchain Consensus Protocol
In the paper, we present designs for multiple blockchain consensus primitives
and a novel blockchain system, all based on the use of trusted execution
environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using
TEEs for existing proof of work schemes can make mining equitably distributed
by preventing the use of ASICs. Next, we extend the design with proof of time
and proof of ownership consensus primitives to make mining energy- and
time-efficient. Further improving on these designs, we present a blockchain
using a proof of luck consensus protocol. Our proof of luck blockchain uses a
TEE platform's random number generation to choose a consensus leader, which
offers low-latency transaction validation, deterministic confirmation time,
negligible energy consumption, and equitably distributed mining. Lastly, we
discuss a potential protection against up to a constant number of compromised
TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital
Precision measurement of the 5 2S1/2 - 4 2D5/2 quadrupole transition isotope shift between 88Sr+ and 86Sr+
We have measured the isotope shift of the narrow quadrupole-allowed 5 2S1/2 -
4 2D5/2 transition in 86Sr+ relative to the most abundant isotope 88Sr+. This
was accomplished using high-resolution laser spectroscopy of individual trapped
ions, and the measured shift is Delta-nu_meas^(88,86) = 570.281(4) MHz. We have
also tested a recently developed and successful method for ab-initio
calculation of isotope shifts in alkali-like atomic systems against this
measurement, and our initial result of Delta-nu_calc^(88,86) = 457(28) MHz is
also presented. To our knowledge, this is the first high precision measurement
and calculation of that isotope shift. While the measurement and the
calculation are in broad agreement, there is a clear discrepancy between them,
and we believe that the specific mass shift was underestimated in our
calculation. Our measurement provides a stringent test for further refinements
of theoretical isotope shift calculation methods for atomic systems with a
single valence electron
Bimaximal Mixings from the Texture of the Right-handed Majorana Neutrino Mass Matrix
We study the origin of neutrino masses and mixing angles which can accomodate
the LMA MSW solutions of the solar neutrino anomaly as well as the solution of
the atmospheric neutrino problem, within the framework of the see-saw
mechanism. We employ the diagonal form of the Dirac neutrino mass matrices with
the physical masses as diagonal elements in the hierarchical order. Such choice
has been motivated from the fact that the known CKM angles for the quark
sector, are relatively small. We consider both possibilities where the Dirac
neutrino mass matrix is either the charged lepton or the up-quark mass matrix
within the framework of SO(10) GUT with or without supersymmetry. The non-zero
texture of the right-handed Majorana neutrino mass matrix is used for
the generation of the desired bimaximal mixings in a model independent way.
Both hierarchical and inverted hierarchical models of the left-handed Majorana
neutrino mass matrices are generated and then discussed with examples
Trimaximal neutrino mixing from vacuum alignment in A4 and S4 models
Recent T2K results indicate a sizeable reactor angle theta_13 which would
rule out exact tri-bimaximal lepton mixing. We study the vacuum alignment of
the Altarelli-Feruglio A4 family symmetry model including additional flavons in
the 1' and 1" representations and show that it leads to trimaximal mixing in
which the second column of the lepton mixing matrix consists of the column
vector (1,1,1)^T/sqrt{3}, with a potentially large reactor angle. In order to
limit the reactor angle and control the higher order corrections, we propose a
renormalisable S4 model in which the 1' and 1" flavons of A4 are unified into a
doublet of S4 which is spontaneously broken to A4 by a flavon which enters the
neutrino sector at higher order. We study the vacuum alignment in the S4 model
and show that it predicts accurate trimaximal mixing with approximate
tri-bimaximal mixing, leading to a new mixing sum rule testable in future
neutrino experiments. Both A4 and S4 models preserve form dominance and hence
predict zero leptogenesis, up to renormalisation group corrections.Comment: 24 pages, 2 figures, version to be published in JHE
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