415 research outputs found
Techni-dilaton at Conformal Edge
Techni-dilaton (TD) was proposed long ago in the technicolor (TC) near
criticality/conformality. To reveal the critical behavior of TD, we explicitly
compute the nonperturbative contributions to the scale anomaly
, which
are generated by the dynamical mass m of the techni-fermions. Our computation
is based on the (improved) ladder Schwinger-Dyson equation, with the gauge
coupling replaced by the two-loop running one having the
Caswell-Banks-Zaks IR fixed point : for the IR region , where is
the intrinsic scale (analogue of of QCD) relevant to the
perturbative scale anomaly. We find that
and in the
criticality limit () ("conformal edge"). Our result precisely
reproduces the formal identity , where is the nonperturbative beta function
corresponding to the above essential singularity scaling of .
Accordingly, the PCDC implies at criticality limit, where is the mass of TD and
the decay constant of TD. We thus conclude that at criticality limit
the TD could become a "true (massless) Nambu-Goldstone boson" ,
only when , namely getting decoupled, as was the case of
"holographic TD" of Haba-Matsuzaki-Yamawaki. The decoupled TD can be a
candidate of dark matter.Comment: 17 pages, 14 figures; discussions clarified, references added, to
appear in Phys.Rev.
Dynamics of QCD in a Strong Magnetic Field
QCD in a strong magnetic field yields an example of a rich, sophisticated and
controllable dynamics.Comment: 12 pages, 1 figure, Latex, Talk at Symposium and Workshop "Continuous
Advances in QCD 2002/Arkadyfest, May 17-23, 200
Toward theory of quantum Hall effect in graphene
We analyze a gap equation for the propagator of Dirac quasiparticles and
conclude that in graphene in a magnetic field, the order parameters connected
with the quantum Hall ferromagnetism dynamics and those connected with the
magnetic catalysis dynamics necessarily coexist (the latter have the form of
Dirac masses and correspond to excitonic condensates). This feature of graphene
could lead to important consequences, in particular, for the existence of
gapless edge states. Solutions of the gap equation corresponding to recently
experimentally discovered novel plateaus in graphene in strong magnetic fields
are described.Comment: 5 pages, no figures, v.2: to match published versio
Thermal conductivity and competing orders in d-wave superconductors
We derive the expression for the thermal conductivity \kappa in the
low-temperature limit T \to 0 in d-wave superconductors, taking into account
the presence of competing orders such as spin-density wave, is-pairing, etc..
The expression is used for analyzing recent experimental data in
La_{2-x}Sr_xCuO_4. Our analysis strongly suggests that competing orders can be
responsible for anomalies in behavior of thermal conductivity observed in those
experiments.Comment: revtex4,6 pages,title changed,references and two eps figures
added,text essentially extended,to appear in EPJ
Chiral dynamics in QED and QCD in a magnetic background and nonlocal noncommutative field theories
We study the connection of the chiral dynamics in QED and QCD in a strong
magnetic field with noncommutative field theories (NCFT). It is shown that
these dynamics determine complicated nonlocal NCFT. In particular, although the
interaction vertices for electrically neutral composites in these gauge models
can be represented in the space with noncommutative spatial coordinates, there
is no field transformation that could put the vertices in the conventional form
considered in the literature. It is unlike the Nambu-Jona-Lasinio (NJL) model
in a magnetic field where such a field transformation can be found, with a cost
of introducing an exponentially damping form factor in field propagators. The
crucial distinction between these two types of models is in the characters of
their interactions, being short-range in the NJL-like models and long-range in
gauge theories. The relevance of the NCFT connected with the gauge models for
the description of the quantum Hall effect in condensed matter systems with
long-range interactions is briefly discussed.Comment: 19 pages, REVTeX4, v2: clarifications added, v3: to match PRD versio
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