8,582 research outputs found
The Chern-Simons Coefficient in Supersymmetric Non-abelian Chern-Simons Higgs Theories
By taking into account the effect of the would be Chern-Simons term, we
calculate the quantum correction to the Chern-Simons coefficient in
supersymmetric Chern-Simons Higgs theories with matter fields in the
fundamental representation of SU(n). Because of supersymmetry, the corrections
in the symmetric and Higgs phases are identical. In particular, the correction
is vanishing for N=3 supersymmetric Chern-Simons Higgs theories. The result
should be quite general, and have important implication for the more
interesting case when the Higgs is in the adjoint representation.Comment: more references and explanation about rgularization dpendence are
included, 13 pages, 1 figure, latex with revte
Kaluza-Klein Induced Gravity Inflation
A D-dimensional induced gravity theory is studied carefully in a
dimensional Friedmann-Robertson-Walker space-time. We try to extract
information of the symmetry breaking potential in search of an inflationary
solution with non-expanding internal-space. We find that the induced gravity
model imposes strong constraints on the form of symmetry breaking potential in
order to generate an acceptable inflationary universe. These constraints are
analyzed carefully in this paper.Comment: 10 pages, title changed, corrected some typos, two additional
comments adde
Anisotropic higher derivative gravity and inflationary universe
Stability analysis of the Kantowski-Sachs type universe in pure higher
derivative gravity theory is studied in details. The non-redundant generalized
Friedmann equation of the system is derived by introducing a reduced one
dimensional generalized KS type action. This method greatly reduces the labor
in deriving field equations of any complicate models. Existence and stability
of inflationary solution in the presence of higher derivative terms are also
studied in details. Implications to the choice of physical theories are
discussed in details in this paper.Comment: 9 page
Inflationary Universe in Higher Derivative Induced Gravity
In an induced-gravity model, the stability condition of an inflationary
slow-rollover solution is shown to be . The presence of higher derivative terms
will, however, act against the stability of this expanding solution unless
further constraints on the field parameters are imposed. We find that these
models will acquire a non-vanishing cosmological constant at the end of
inflation. Some models are analyzed for their implication to the early
universe.Comment: 6 pages, two typos correcte
Kaluza-Klein Higher Derivative Induced Gravity
The existence and stability analysis of an inflationary solution in a
-dimensional anisotropic induced gravity is presented in this paper.
Nontrivial conditions in the field equations are shown to be compatible with a
cosmological model in which the 4-dimension external space evolves
inflationary, while, the D-dimension internal one is static. In particular,
only two additional constraints on the coupling constants are derived from the
abundant field equations and perturbation equations. In addition, a compact
formula for the non-redundant 4+D dimensional Friedmann equation is also
derived for convenience. Possible implications are also discussed in this
paper.Comment: 13 pages, typos/errors corrected, three additional appendices adde
Electronic structure and magnetic properties of epitaxial FeRh(001) ultra-thin films on W(100)
Epitaxial FeRh(100) films (CsCl structure, thick), prepared
{\it in-situ} on a W(100) single crystal substrate, have been investigated via
valence band and core level photoemission. The presence of the
temperature-induced, first-order, antiferromagnetic to ferromagnetic
(AF FM) transition in these films has been verified via linear
dichroism in photoemission from the Fe 3 levels. Core level spectra indicate
a large moment on the Fe atom, practically unchanged in the FM and AF phases.
Judging from the valence band spectra, the metamagnetic transition takes place
without substantial modification of the electronic structure. In the FM phase,
the spin-resolved spectra compare satisfactorily to the calculated
spin-polarized bulk band structure.Comment: 7 pages, 5 figure
Lepton Flavor Violation and Cosmological Constraints on R-parity Violation
In supersymmetric standard models R-parity violating couplings are severely
constrained, since otherwise they would erase the existing baryon asymmetry
before the electroweak transition. It is often claimed that this cosmological
constraint can be circumvented if the baryon number and one of the lepton
flavor numbers are sufficiently conserved in these R-parity violating
couplings, because B/3-L_i for each lepton flavor is separately conserved by
the sphaleron process. We discuss the effect of lepton flavor violation on the
B-L conservation, and show that even tiny slepton mixing angles \theta_{12}
\gsim {\cal O}(10^{-4}) and \theta_{23}, \theta_{13}\gsim {\cal O}(10^{-5})
will spoil the separate B/3-L_i conservation. In particular, if lepton flavor
violations are observed in experiments such as MEG and B-factories, it will
imply that all the R-parity violating couplings must be suppressed to avoid the
B-L erasure. We also discuss the implication for the decay of the lightest MSSM
particle at the LHC.Comment: 21 pages, 7 figures. v2: minor change
Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space
Stability analysis of the Bianchi type I universe in pure gravity theory is
studied in details. We first derive the non-redundant field equation of the
system by introducing the generalized Bianchi type I metric. This non-redundant
equation reduces to the Friedmann equation in the isotropic limit. It is shown
further that any unstable mode of the isotropic perturbation with respect to a
de Sitter background is also unstable with respect to anisotropic
perturbations. Implications to the choice of physical theories are discussed in
details in this paper.Comment: 5 pages, some comment adde
Improving 3D U-Net for Brain Tumor Segmentation by Utilizing Lesion Prior
We propose a novel, simple and effective method to integrate lesion prior and
a 3D U-Net for improving brain tumor segmentation. First, we utilize the
ground-truth brain tumor lesions from a group of patients to generate the
heatmaps of different types of lesions. These heatmaps are used to create the
volume-of-interest (VOI) map which contains prior information about brain tumor
lesions. The VOI map is then integrated with the multimodal MR images and input
to a 3D U-Net for segmentation. The proposed method is evaluated on a public
benchmark dataset, and the experimental results show that the proposed feature
fusion method achieves an improvement over the baseline methods. In addition,
our proposed method also achieves a competitive performance compared to
state-of-the-art methods.Comment: 5 pages, 4 figures, 1 table, LNCS forma
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