13,545 research outputs found
Symmetry Principle Preserving and Infinity Free Regularization and renormalization of quantum field theories and the mass gap
Through defining irreducible loop integrals (ILIs), a set of consistency
conditions for the regularized (quadratically and logarithmically) divergent
ILIs are obtained to maintain the generalized Ward identities of gauge
invariance in non-Abelian gauge theories. Overlapping UV divergences are
explicitly shown to be factorizable in the ILIs and be harmless via suitable
subtractions. A new regularization and renormalization method is presented in
the initial space-time dimension of the theory. The procedure respects
unitarity and causality. Of interest, the method leads to an infinity free
renormalization and meanwhile maintains the symmetry principles of the original
theory except the intrinsic mass scale caused conformal scaling symmetry
breaking and the anomaly induced symmetry breaking. Quantum field theories
(QFTs) regularized through the new method are well defined and governed by a
physically meaningful characteristic energy scale (CES) and a physically
interesting sliding energy scale (SES) which can run from to a dynamically generated mass gap or to in the
absence of mass gap and infrared (IR) problem. It is strongly indicated that
the conformal scaling symmetry and its breaking mechanism play an important
role for understanding the mass gap and quark confinement.Comment: 59 pages, Revtex, 4 figures, 1 table, Erratum added, published
versio
Roles and mechanisms of the CD38/cyclic adenosine diphosphate ribose/Ca2+ signaling pathway
published_or_final_versio
Self-consistent tilted-axis-cranking study of triaxial strongly deformed bands in Er at ultrahigh spin
Stimulated by recent experimental discoveries, triaxial strongly deformed
(TSD) states in Er at ultrahigh spins have been studied by means of the
Skyrme-Hartree-Fock model and the tilted-axis-cranking method. Restricting the
rotational axis to one of the principal axes -- as done in previous cranking
calculations -- two well-defined TSD minima in the total Routhian surface are
found for a given configuration: one with positive and another with negative
triaxial deformation . By allowing the rotational axis to change
direction, the higher-energy minimum is shown to be a saddle point. This
resolves the long-standing question of the physical interpretation of the two
triaxial minima at a very similar quadrupole shape obtained in the principal
axis cranking approach. Several TSD configurations have been predicted,
including a highly deformed band expected to cross lesser elongated TSD bands
at the highest spins. Its transitional quadrupole moment \,eb
is close to the measured value of 11\,eb; hence, it is a candidate for
the structure observed in experiment.Comment: 5 pages, 5 figure
Slave particle approach to the finite temperature properties of ultracold Bose gases in optical lattices
By using slave particle (slave boson and slave fermion) technique on the
Bose-Hubbard model, we study the finite temperature properties of ultracold
Bose gases in optical lattices. The phase diagrams at finite temperature are
depicted by including different types of slave particles and the effect of the
finite types of slave particles is estimated. The superfluid density is
evaluated using the Landau second order phase transition theory. The atom
density, excitation spectrum and dispersion curve are also computed at various
temperatures, and how the Mott-insulator evolves as the temperature increases
is demonstrated. For most quantities to be calculated, we find that there are
no qualitatively differences in using the slave boson or the slave fermion
approaches. However, when studying the stability of the mean field state, we
find that in contrast to the slave fermion approach, the slave boson mean field
state is not stable. Although the slave boson mean field theory gives a
qualitatively correct phase boundary, it corresponds to a local maximum of
Landau free energy and can not describe the second order phase transition
because the coefficient of the fourth order term is always negative in
the free energy expansion.Comment: 27 pages, 8 figures, final version for publicatio
Parametrical optimization of laser surface alloyed NiTi shape memory alloy with Co and Nb by the Taguchi method
Different high-purity metal powders were successfully alloyed on to a nickel titanium (NiTi) shape memory alloy (SMA) with a 3 kW carbon dioxide (CO2) laser system. In order to produce an alloyed layer with complete penetration and acceptable composition profile, the Taguchi approach was used as a statistical technique for optimizing selected laser processing parameters. A systematic study of laser power, scanning velocity, and pre-paste powder thickness was conducted. The signal-to-noise ratios (S/N) for each control factor were calculated in order to assess the deviation from the average response. Analysis of variance (ANOVA) was carried out to understand the significance of process variables affecting the process effects. The Taguchi method was able to determine the laser process parameters for the laser surface alloying technique with high statistical accuracy and yield a laser surface alloying technique capable of achieving a desirable dilution ratio. Energy dispersive spectrometry consistently showed that the per cent by weight of Ni was reduced by 45 per cent as compared with untreated NiTi SMA when the Taguchi-determined laser processing parameters were employed, thus verifying the laser's processing parameters as optimum
The scalars from the topcolor scenario and the spin correlations of the top pair production at the LHC
The topcolor scenario predicts the existences of some new scalars. In this
paper, we consider the contributions of these new particles to the observables,
which are related to the top quark pair () production at the LHC. It
is found that these new particles can generate significant corrections to the
production cross section and the spin correlations.Comment: 23 pages, 4 figures; discussions and references added; agrees with
published versio
Probing Topcolor-Assisted Technicolor from Like-sign Top Pair Production at LHC
The topcolor-assisted technicolor (TC2) theory predicts tree-level
flavor-changing neutral-current (FCNC) top quark Yukawa couplings with
top-pions. Such FCNC interactions will induce like-sign top quark pair
productions at CERN Large Hadron Collider (LHC). While these rare productions
are far below the observable level in the Standard Model and other popular new
physics models such as the Minimal Supersymmetric Model, we find that in a
sound part of parameter space the TC2 model can enhance the production cross
sections to several tens of fb and thus may be observable at the LHC due to
rather low backgrounds. Searching for these productions at the LHC will serve
as an excellent probe for the TC2 model.Comment: 10 pages, 6 fig
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