197 research outputs found
Lie algebroid structures on a class of affine bundles
We introduce the notion of a Lie algebroid structure on an affine bundle
whose base manifold is fibred over the real numbers. It is argued that this is
the framework which one needs for coming to a time-dependent generalization of
the theory of Lagrangian systems on Lie algebroids. An extensive discussion is
given of a way one can think of forms acting on sections of the affine bundle.
It is further shown that the affine Lie algebroid structure gives rise to a
coboundary operator on such forms. The concept of admissible curves and
dynamical systems whose integral curves are admissible, brings an associated
affine bundle into the picture, on which one can define in a natural way a
prolongation of the original affine Lie algebroid structure.Comment: 28 page
Driven cofactor systems and Hamilton-Jacobi separability
This is a continuation of the work initiated in a previous paper on so-called
driven cofactor systems, which are partially decoupling second-order
differential equations of a special kind. The main purpose in that paper was to
obtain an intrinsic, geometrical characterization of such systems, and to
explain the basic underlying concepts in a brief note. In the present paper we
address the more intricate part of the theory. It involves in the first place
understanding all details of an algorithmic construction of quadratic integrals
and their involutivity. It secondly requires explaining the subtle way in which
suitably constructed canonical transformations reduce the Hamilton-Jacobi
problem of the (a priori time-dependent) driven part of the system into that of
an equivalent autonomous system of St\"ackel type
Algebraic theories of brackets and related (co)homologies
A general theory of the Frolicher-Nijenhuis and Schouten-Nijenhuis brackets
in the category of modules over a commutative algebra is described. Some
related structures and (co)homology invariants are discussed, as well as
applications to geometry.Comment: 14 pages; v2: minor correction
Tetrad gravity, electroweak geometry and conformal symmetry
A partly original description of gauge fields and electroweak geometry is
proposed. A discussion of the breaking of conformal symmetry and the nature of
the dilaton in the proposed setting indicates that such questions cannot be
definitely answered in the context of electroweak geometry.Comment: 21 pages - accepted by International Journal of Geometric Methods in
Modern Physics - v2: some minor changes, mostly corrections of misprint
Many parameter Hoelder perturbation of unbounded operators
If is a -mapping, for , having
as values unbounded self-adjoint operators with compact resolvents and common
domain of definition, parametrized by in an (even infinite dimensional)
space, then any continuous (in ) arrangement of the eigenvalues of is
indeed in .Comment: LaTeX, 4 pages; The result is generalized from Lipschitz to Hoelder.
Title change
Local Drivers of Marine Heatwaves: A Global Analysis With an Earth System Model
Marine heatwaves (MHWs) are periods of extreme warm ocean temperatures that can have devastating impacts on marine organisms and socio-economic systems. Despite recent advances in understanding the underlying processes of individual events, a global view of the local oceanic and atmospheric drivers of MHWs is currently missing. Here, we use daily-mean output of temperature tendency terms from a comprehensive fully coupled coarse-resolution Earth system model to quantify the main local processes leading to the onset and decline of surface MHWs in different seasons. The onset of MHWs in the subtropics and mid-to-high latitudes is primarily driven by net ocean heat uptake associated with a reduction of latent heat loss in all seasons, increased shortwave heat absorption in summer and reduced sensible heat loss in winter, dampened by reduced vertical mixing from the non-local portion of the K-Profile Parameterization boundary layer scheme (KPP) especially in summer. In the tropics, ocean heat uptake is reduced and lowered vertical local mixing and diffusion cause the warming. In the subsequent decline phase, increased ocean heat loss to the atmosphere due to enhanced latent heat loss in all seasons together with enhanced vertical local mixing and diffusion in the high latitudes during summer dominate the temperature decrease globally. The processes leading to the onset and decline of MHWs are similar for short and long MHWs, but there are differences in the drivers between summer and winter. Different types of MHWs with distinct driver combinations are identified within the large variability among events. Our analysis contributes to a better understanding of MHW drivers and processes and may therefore help to improve the prediction of high-impact marine heatwaves
The Stratified Structure of Spaces of Smooth Orbifold Mappings
We consider four notions of maps between smooth C^r orbifolds O, P with O
compact (without boundary). We show that one of these notions is natural and
necessary in order to uniquely define the notion of orbibundle pullback. For
the notion of complete orbifold map, we show that the corresponding set of C^r
maps between O and P with the C^r topology carries the structure of a smooth
C^\infty Banach (r finite)/Frechet (r=infty) manifold. For the notion of
complete reduced orbifold map, the corresponding set of C^r maps between O and
P with the C^r topology carries the structure of a smooth C^\infty Banach (r
finite)/Frechet (r=infty) orbifold. The remaining two notions carry a
stratified structure: The C^r orbifold maps between O and P is locally a
stratified space with strata modeled on smooth C^\infty Banach (r
finite)/Frechet (r=infty) manifolds while the set of C^r reduced orbifold maps
between O and P locally has the structure of a stratified space with strata
modeled on smooth C^\infty Banach (r finite)/Frechet (r=infty) orbifolds.
Furthermore, we give the explicit relationship between these notions of
orbifold map. Applying our results to the special case of orbifold
diffeomorphism groups, we show they inherit the structure of C^\infty Banach (r
finite)/Frechet (r=infty) manifolds. In fact, for r finite they are topological
groups, and for r=infty they are convenient Frechet Lie groups.Comment: 31 pages, 2 figures; corrected and expande
Impact of deoxygenation and warming on global marine species in the 21st century
Ocean temperature and dissolved oxygen shape marine
habitats in an interplay with species' physiological characteristics.
Therefore, the observed and projected warming and deoxygenation of the
world's oceans in the 21st century may strongly affect species'
habitats. Here, we implement an extended version of the Aerobic Growth Index
(AGI), which quantifies whether a viable population of a species can be
sustained in a particular location. We assess the impact of projected
deoxygenation and warming on the contemporary habitat of 47 representative
marine species covering the epipelagic, mesopelagic, and demersal realms.
AGI is calculated for these species for the historical period and into the
21st century using bias-corrected environmental data from six
comprehensive Earth system models. While habitat viability decreases nearly
everywhere with global warming, the impact of this decrease is strongly
species dependent. Most species lose less than 5â% of their contemporary
habitat volume at 2ââC of global
warming relative to preindustrial levels, although some individual species are
projected to incur losses 2â3 times greater than that. We find that the
in-habitat spatiotemporal variability of O2 and temperature (and hence
AGI) provides a quantifiable measure of a species' vulnerability to change.
In the event of potential large habitat losses (over 5â%), species
vulnerability is the most important indicator. Vulnerability is more
critical than changes in habitat viability, temperature, or pO2 levels.
Loss of contemporary habitat is for most epipelagic species driven by the
warming of ocean water and is therefore elevated with increased levels of
global warming. In the mesopelagic and demersal realms, habitat loss is also
affected by pO2 decrease for some species. Our analysis is constrained
by the uncertainties involved in species-specific critical thresholds, which
we quantify; by data limitations on 3D species distributions; and by
high uncertainty in model O2 projections in equatorial regions. A focus
on these topics in future research will strengthen our confidence in
assessing climate-change-driven losses of contemporary habitats across the
global oceans.</p
Concurrent -vector fields and energy beta-change
The present paper deals with an \emph{intrinsic} investigation of the notion
of a concurrent -vector field on the pullback bundle of a Finsler manifold
. The effect of the existence of a concurrent -vector field on some
important special Finsler spaces is studied. An intrinsic investigation of a
particular -change, namely the energy -change
($\widetilde{L}^{2}(x,y)=L^{2}(x,y)+ B^{2}(x,y) with \
B:=g(\bar{\zeta},\bar{\eta})\bar{\zeta} \pi\Gamma\widetilde{\Gamma}\beta$-change of the fundamental linear connection in Finsler geometry: the
Cartan connection, the Berwald connection, the Chern connection and the
Hashiguchi connection. Moreover, the change of their curvature tensors is
concluded.
It should be pointed out that the present work is formulated in a prospective
modern coordinate-free form.Comment: 27 pages, LaTex file, Some typographical errors corrected, Some
formulas simpifie
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