419 research outputs found
Baryon charge from embedding topology and a continuous meson spectrum in a new holographic gauge theory
We study a new holographic gauge theory based on probe D4-branes in the
background dual to D4-branes on a circle with antiperiodic boundary conditions
for fermions. Field theory configurations with baryons correspond to smooth
embeddings of the probe D4-branes with nontrivial winding around an S^4 in the
geometry. As a consequence, physics of baryons and nuclei can be studied
reliably in this model using the abelian Born-Infeld action. However,
surprisingly, we find that the meson spectrum is not discrete. This is related
to a curious result that the action governing small fluctuations of the gauge
field on the probe brane is the five-dimensional Maxwell action in Minkowski
space despite the non-trivial embedding of the probe brane in the curved
background geometry.Comment: 24 pages, LaTeX, 10 figures, v4: previously ignored effects of
coupling to RR-fields included, meson spectrum qualitatively changed, v5:
journal versio
Well-Posedness for Semi-Relativistic Hartree Equations of Critical Type
We prove local and global well-posedness for semi-relativistic, nonlinear
Schr\"odinger equations with
initial data in , . Here is a critical
Hartree nonlinearity that corresponds to Coulomb or Yukawa type
self-interactions. For focusing , which arise in the quantum theory of
boson stars, we derive a sufficient condition for global-in-time existence in
terms of a solitary wave ground state. Our proof of well-posedness does not
rely on Strichartz type estimates, and it enables us to add external potentials
of a general class.Comment: 18 pages; replaced with revised version; remark and reference on blow
up adde
Skyrmions with holography and hidden local symmetry
We study baryons as Skyrmions in holographic QCD with D4/D8/D8-bar multi-D
brane system in type IIA superstring theory, and also in the non-linear sigma
model with hidden local symmetry (HLS). Comparing these two models, we find
that the extra-dimension and its nontrivial curvature can largely change the
role of (axial) vector mesons for baryons in four-dimensional space-time. In
the HLS approach, the rho-meson field as a massive Yang-Mills field has a
singular configuration in Skyrmion, which gives a strong repulsion for the
baryon as a stabilizer. When a_1 meson is added in this approach, the stability
of Skyrmion is lost by the cancellation of rho and a_1 contributions. On the
contrary, in holographic QCD, the rho-meson field does not appear as a massive
Yang-Mills field due to the extra-dimension and its nontrivial curvature. We
show that the rho-meson field has a regular configuration in Skyrmion, which
gives a weak attraction for the baryon in holographic QCD. We argue that
Skyrmion with pi, rho and a_1 mesons become stable due to the curved
extra-dimension and also the presence of the Skyrme term in holographic QCD.
From this result, we also discuss the features of our truncated-resonance
analysis on baryon properties with pi and rho mesons below the cutoff scale
M_KK about 1GeV in holographic QCD, which is compared with other 5D instanton
analysis.Comment: 7 pages, 7 figure
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