21 research outputs found
Exciton Condensation in a Holographic Double Monolayer Semimetal
The formation of intra-layer and inter-layer exciton condensates in a model
of a double monolayer Weyl semi-metal is studied in the strong coupling limit
using AdS/CFT duality. We find a rich phase diagram which includes phase
transitions between inter-layer and intra-layer condensates as the charge
densities and the separation of the layers are varied. The tendency to
inter-layer condensation is strongest when the charge densities are balanced so
that the weak coupling electron and hole Fermi surfaces would be nested. For
systems with multiple species of massless Fermions, we find a novel phase
transition where the charge balance for nesting occurs spontaneously.Comment: 4 pages, 2 figure
Holographic D3-probe-D5 Model of a Double Layer Dirac Semimetal
The possibility of inter-layer exciton condensation in a holographic
D3-probe-D5 brane model of a strongly coupled double monolayer Dirac semi-metal
in a magnetic field is studied in detail. It is found that, when the charge
densities on the layers are exactly balanced so that, at weak coupling, the
Fermi surfaces of electrons in one monolayer and holes in the other monolayer
would be perfectly nested, inter-layer condensates can form for any separation
of the layers. The case where both monolayers are charge neutral is special.
There, the inter-layer condensate occurs only for small separations and is
replaced by an intra-layer exciton condensate at larger separations. The phase
diagram for charge balanced monolayers for a range layer separations and
chemical potentials is found. We also show that, in semi-metals with multiple
species of massless fermions, the balance of charges required for Fermi surface
nesting can occur spontaneously by breaking some of the internal symmetry of
the monolayers. This could have important consequences for experimental
attempts to find inter-layer condensates.Comment: minor correction to reference
Seismic performance of reinforced concrete frames retrofitted with inserted steel frame and adhered waved steel panel
In this paper, two types of seismic retrofitting methods for reinforced concrete frames were suggested and examined through the cyclic loading tests: one is to insert a steel frame to existing partially masonry infilled concrete frame of the building after removing masonry from the concrete frame and the other is to adhere waved steel panels to the existing masonry fully infilled concrete frame. In order to evaluate validity of the suggested methods in seismic performance, five specimens were manufactured and tested: a bare concrete frame, a partially masonry infilled concrete frame, a masonry infilled concrete frame, a steel frame inserted concrete frame, and a waved steel panel adhered concrete frame. Compared were crack pattern, failure mode, load-displacement relation, ductility, stiffness and energy dissipation capacity. The specimens retrofitted with the inserted steel frame showed a maximum load approximately twice that of the partially masonry infilled frame, and the specimen retrofitted with the adhered waved steel panel showed a maximum load approximately twice that of the masonry fully infilled frame
D3-D5 Holography with Flux
It is shown that the Berezinski-Kosterlitz-Thouless phase transition that has
been found in D3-D5 brane systems with nonzero magnetic field and charge
density can also be found by tuning an extra-dimensional magnetic flux. We find
numerical solutions for the probe D5-brane embedding and discuss properties of
the solutions. We also demonstrate that the nontrivial embeddings include those
which can be regarded as spontaneously breaking chiral symmetry
Seismic performance of reinforced concrete frames retrofitted with inserted steel frame and adhered waved steel panel
In this paper, two types of seismic retrofitting methods for reinforced concrete frames were suggested and examined through the cyclic loading tests: one is to insert a steel frame to existing partially masonry infilled concrete frame of the building after removing masonry from the concrete frame and the other is to adhere waved steel panels to the existing masonry fully infilled concrete frame. In order to evaluate validity of the suggested methods in seismic performance, five specimens were manufactured and tested: a bare concrete frame, a partially masonry infilled concrete frame, a masonry infilled concrete frame, a steel frame inserted concrete frame, and a waved steel panel adhered concrete frame. Compared were crack pattern, failure mode, load-displacement relation, ductility, stiffness and energy dissipation capacity. The specimens retrofitted with the inserted steel frame showed a maximum load approximately twice that of the partially masonry infilled frame, and the specimen retrofitted with the adhered waved steel panel showed a maximum load approximately twice that of the masonry fully infilled frame
D7-anti-D7 bilayer: holographic dynamical symmetry breaking
We consider a holographic model of dynamical symmetry breaking in
2+1-dimenisons, where a parallel D7-anti-D7 brane pair fuse into a single
object, corresponding to the U(1)XU(1)->U(1) symmetry breaking pattern. We show
that the current-current correlation functions can be computed analytically and
exhibit the low momentum structure that is expected when global symmetries are
spontaneously broken. We also find that these correlation functions have poles
attributable to infinite towers of vector mesons with equally spaced masses.Comment: 4 pages, 3 figure
Flavor-symmetry Breaking with Charged Probes
We discuss the recombination of brane/anti-brane pairs carrying brane
charge in . These configurations are dual to co-dimension one
defects in the super-Yang-Mills description. Due to their
charge, these defects are actually domain walls in the dual gauge theory,
interpolating between vacua of different gauge symmetry. A pair of unjoined
defects each carry localized dimensional fermions and possess a global
flavor symmetry while the recombined brane/anti-brane pairs
exhibit only a diagonal U(N). We study the thermodynamics of this
flavor-symmetry breaking under the influence of external magnetic field.Comment: 21 pages, 10 figure
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Long non-coding RNA ChRO1 facilitates ATRX/DAXX-dependent H3.3 deposition for transcription-associated heterochromatin reorganization.
Constitutive heterochromatin undergoes a dynamic clustering and spatial reorganization during myogenic differentiation. However the detailed mechanisms and its role in cell differentiation remain largely elusive. Here, we report the identification of a muscle-specific long non-coding RNA, ChRO1, involved in constitutive heterochromatin reorganization. ChRO1 is induced during terminal differentiation of myoblasts, and is specifically localized to the chromocenters in myotubes. ChRO1 is required for efficient cell differentiation, with global impacts on gene expression. It influences DNA methylation and chromatin compaction at peri/centromeric regions. Inhibition of ChRO1 leads to defects in the spatial fusion of chromocenters, and mislocalization of H4K20 trimethylation, Suv420H2, HP1, MeCP2Â and cohesin. In particular, ChRO1 specifically associates with ATRX/DAXX/H3.3 complex at chromocenters to promote H3.3 incorporation and transcriptional induction of satellite repeats, which is essential for chromocenter clustering. Thus, our results unveil a mechanism involving a lncRNA that plays a role in large-scale heterochromatin reorganization and cell differentiation.Individual Basic Researcher Program [2018R1D1A1B070 48056 to E.-J.C., 2017R1D1A1B03035883 to J.P.]; Advanced Research Center Program [NRF-2010-0029359 to E.-J.C.]; National Creative Research Laboratory Program [2012R1A3A2048767 to H.-D.Y.]; NRF-2012-Fostering Core Leaders of the Future Basic Science Program through the National Research Foundation of Korea [2012H1A8003093 to J.P.]