4,469 research outputs found
Fractionalization, topological order, and quasiparticle statistics
We argue, based on general principles, that topological order is essential to
realize fractionalization in gapped insulating phases in dimensions .
In with genus , we derive the existence of the minimum topological
degeneracy if the charge is fractionalized in unit of , irrespective
of microscopic model or of effective theory. Furthermore, if the quasiparticle
is either boson or fermion, it must be at least .Comment: 4 pages, updated with additional references. No change in the main
conclusio
Mass ratio of elementary excitations in frustrated antiferromagnetic chains with dimerization
Excitation spectra of S=1/2 and S=1 frustrated Heisenberg antiferromagnetic
chains with bond alternation (explicit dimerization) are studied using a
combination of analytical and numerical methods. The system undergoes a
dimerization transition at a critical bond alternation parameter
, where for the S=1/2 chain. The
SU(2)-symmetric sine-Gordon theory is known to be an effective field theory of
the system except at the transition point. The sine-Gordon theory has a
SU(2)-triplet and a SU(2)-singlet of elementary excitation, and the mass ratio
of the singlet to the triplet is . However, our numerical
calculation with the infinite time-evolving block decimation method shows that
depends on the frustration (next-nearest-neighbor coupling) and is
generally different from . This can be understood as an effect of
marginal perturbation to the sine-Gordon theory. In fact, at the critical
frustration separating the second-order and first-order dimerization
transitions, the marginal operator vanishes and holds. We derive
the mass ratio analytically using form-factor perturbation theory combined
with a renormalization-group analysis. Our formula agrees well with the
numerical results, confirming the theoretical picture. The present theory also
implies that, even in the presence of a marginally irrelevant operator, the
mass ratio approaches in the very vicinity of the second-order
dimerization critical point . However, such a region is
extremely small and would be difficult to observe numerically.Comment: 7 pages, 5 figure
Cosmologically safe QCD axion as a present from extra dimension
We propose a QCD axion model where the origin of PQ symmetry and suppression
of axion isocurvature perturbations are explained by introducing an extra
dimension. Each extra quark-antiquark pair lives on branes separately to
suppress PQ breaking operators. The size of the extra dimension changes after
inflation due to an interaction between inflaton and a bulk scalar field, which
implies that the PQ symmetry can be drastically broken during inflation to
suppress undesirable axion isocurvature fluctuations.Comment: 6 page
Diphoton Excess as a Hidden Monopole
We provide a theory with a monopole of a strongly-interacting hidden U(1)
gauge symmetry that can explain the 750-GeV diphoton excess reported by ATLAS
and CMS. The excess results from the resonance of monopole, which is produced
via gluon fusion and decays into two photons. In the low energy, there are only
mesons and a monopole in our model because any baryons cannot be gauge
invariant in terms of strongly interacting Abelian symmetry. This is
advantageous of our model because there is no unwanted relics around the BBN
epoch.Comment: 6 pages, 1 figur
Unification of the Standard Model and Dark Matter Sectors in [SU(5)U(1)]
A simple model of dark matter contains a light Dirac field charged under a
hidden U(1) gauge symmetry. When a chiral matter content in a strong dynamics
satisfies the t'Hooft anomaly matching condition, a massless baryon is a
natural candidate of the light Dirac field. One realization is the same matter
content as the standard SU(5)U(1) grand unified theory. We
propose a chiral [SU(5)U(1)] gauge theory as a unified model of the
SM and DM sectors. The low-energy dynamics, which was recently studied, is
governed by the hidden U(1) gauge interaction and the third-family
U(1) gauge interaction. This model can realize self-interacting
dark matter and alleviate the small-scale crisis of collisionless cold dark
matter in the cosmological structure formation. The model can also address the
semi-leptonic -decay anomaly reported by the LHCb experiment.Comment: 15 pages, 2 figure
Alcohol Myopia and Risk Taking
The aim of this paper is to develop a model that explains how the consumption of some additive substances a¤ects an individual?s choice between risky alternatives. We do this by assuming that some additives substances, speci?cally alcohol, increase individual?s present bias. As individuals that consume alcohol show greater preference for the present and less for the future, they would ?nd risky choices with rewards in the present and costs in the future more attractive. Theferore, an individual that wouldn´t have accepted a lottery may do so after consuming alcohol and he regret his decision after the alcohol in his blood is eliminated. We analyze the e¤ect of two taxes in discouraging a risky activity: a tax on the consumption of alcohol and a tax (or penalty) if the future costs of the lottery are realized.habit-formation, risk taking, alcohol consumption
Interaction of massless Dirac field with a Poincar\'e gauge field
In this paper we consider a model of Poincar\'e gauge theory (PGT) in which a
translational gauge field and a Lorentz gauge field are actually identified
with the Einstein's gravitational field and a pair of ``Yang-Mills'' field and
its partner, respectively.In this model we re-derive some special solutions and
take up one of them. The solution represents a ``Yang-Mills'' field without its
partner field and the Reissner-Nordstr\"om type spacetime, which are generated
by a PGT-gauge charge and its mass.It is main purpose of this paper to
investigate the interaction of massless Dirac fields with those fields. As a
result, we find an interesting fact that the left-handed massless Dirac fields
behave in the different manner from the right-handed ones. This can be
explained as to be caused by the direct interaction of Dirac fields with the
``Yang-Mills'' field. Accordingly, the phenomenon can not happen in the
behavior of the neutrino waves in ordinary Reissner-Nordstr\"om geometry. The
difference between left- and right-handed effects is calculated quantitatively,
considering the scattering problems of the massless Dirac fields by our
Reissner-Nordstr\"om type black-hole.Comment: 10pages, RevTeX3.
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