36 research outputs found
Field theories on spaces with linear fuzziness
A noncommutative space is considered the position operators of which satisfy
the commutativity relations of a Lie algebra. The basic tools for calculation
on this space, including the product of the fields, inner product and the
proper measure for integration are derived. Some general aspects of
perturbative field theory calculations on this space are also discussed. Among
the features of such models is that they are free from ultraviolet divergences
(and hence free from UV/IR mixing as well), if the group is compact. The
example of the group SO(3) or SU(2) is investigated in more detail.Comment: 12 pages, no figs., LaTeX. v2: Comments and discussions are added,
e.g. on absence of UV/IR phenomena. No change in result
Interacting Spinors-Scalars and AdS/CFT Correspondence
By taking the interacting spinor-scalar theory on the space we
calculate the boundary CFT correlation functions using AdS/CFT correspondence.Comment: The crucial role of the surface term in the action to generate the
correlation functions quadratic in spinors is considered. LaTeX file, 8 page
On The Interaction Of D0-Brane Bound States And RR Photons
We consider the problem of the interaction between D0-brane bound state and
1-form RR photons by the world-line theory. Based on the fact that in the
world-line theory the RR gauge fields depend on the matrix coordinates of
D0-branes, the gauge fields also appear as matrices in the formulation. At the
classical level, we derive the Lorentz-like equations of motion for D0-branes,
and it is observed that the center-of-mass is colourless with respect to the
SU(N) sector of the background. Using the path integral method, the
perturbation theory for the interaction between the bound state and the RR
background is developed. We discuss what kind of field theory may be
corresponded to the amplitudes which are calculated by the perturbation
expansion in world-line theory. Qualitative considerations show that the
possibility of existence of a map between the world-line theory and the
non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are
corrected, very small change
Non-Commutative Geometry and Chiral Perturbation Lagrangian
Chiral perturbation lagrangian in the framework of non-commutative geometry
is considered in full detail. It is found that the explicit symmetry breaking
terms appear and some relations between the coupling constants of the theory
come out naturally. The WZW term also turns up on the same footing as the other
terms of the chiral lagrangian.Comment: Latex, 9 page
TeV-photon paradox and space with SU(2) fuzziness
The possibility is examined that a model based on space noncommutativity of
linear type can explain why photons from distant sources with multi-TeV
energies can reach earth. In particular within a model in which space
coordinates satisfy the algebra of SU(2) Lie group, it is shown that there is
the possibility that the pair production through the reaction of CMB and
energetic photons would be forbidden kinematically.Comment: 11 pages, no fig., LaTe
Star Product and Invariant Integration for Lie type Noncommutative Spacetimes
We present a star product for noncommutative spaces of Lie type, including
the so called ``canonical'' case by introducing a central generator, which is
compatible with translations and admits a simple, manageable definition of an
invariant integral. A quasi-cyclicity property for the latter is shown to hold,
which reduces to exact cyclicity when the adjoint representation of the
underlying Lie algebra is traceless. Several explicit examples illuminate the
formalism, dealing with kappa-Minkowski spacetime and the Heisenberg algebra
(``canonical'' noncommutative 2-plane).Comment: 21 page
Long term training on sand changes lower limb muscle activities during running in runners with over-pronated feet
This is the final version. Available on open access from BMC via the DOI in this recordAvailability of data and materials;
The data sets used and/or analyzed during the current study are available from the corresponding author on reasonable request.Background
Running on sand could be a promising exercise intervention for the treatment of over-pronated feet. However, there is a lack of knowledge about the effects of running on sand on muscle activities. Therefore, this study aims to evaluate the long-term effects of running on sand on the activities of selected lower limb muscles in individuals with OPF compared with healthy controls.
Methods
Sixty recreational adult male runners with over-pronated feet (foot posture index > 10) were divided into two equal groups (intervention and control). Participants ran barefoot at a pre-defined speed (⁓3.3 m/s) over level stable ground both before and after long-term training on the sand. Muscle activities were recorded using a surface bipolar electromyography system.
Results
For the intervention group, we found a reduced foot posture index (p < 0.001; d = 2.00) and significant group-by-time interactions for gluteus medius activity during the mid-stance phase (p < 0.028; d = 0.59). Significantly higher gluteus medius activity (p = 0.028, d = 0.569) was found during the post-test. We also observed significant group-by-time interactions for medial gastrocnemius activity during the push-off phase (p < 0.041; d = 0.54). Significantly larger medial gastrocnemius activity (p = 0.041; d = 0.636) was found during the post-test compared to the pre-test.
Conclusions
Long-term running on sand resulted in reduced pronation, increased medial gastrocnemius activity, and improved frontal plane pelvic stability due to higher gluteus medius activity.
Trial registration: IRCT20191211045704N1. Registered 25 February 2020. Retrospectively registered
Multispecies reaction-diffusion systems
Multispecies reaction-diffusion systems, for which the time evolution
equation of correlation functions become a closed set, are considered. A formal
solution for the average densities is found. Some special interactions and the
exact time dependence of the average densities in these cases are also studied.
For the general case, the large time behaviour of the average densities has
also been obtained.Comment: LaTeX file, 15 pages, to appear in Phys. Rev.
Do Quarks Obey D-Brane Dynamics?
The potential between two D0-branes at rest is calculated to be a linear.
Also the potential between two fast decaying D0-branes is found in agreement
with phenomenological heavy-quark potentials.Comment: 7 pages, no figures, LaTe