arXiv research

Study on Carter spacetime's causal properties, proving infinite time-separation.

Carter tensor analysis aids wave equation on Kerr-Newman spacetime.

RNN beats Lee-Carter in forecasting mortality rates.

Paper uses neural networks to calibrate Lee-Carter models for multiple populations.

The Lee Carter modelling framework is widely used because of its simplicity and robustness despite its inability to model specific cohort effects. A large number of extensions have been proposed that model cohort effects but there is no consensus. It is difficult to simultaneously account for cohort effects and age-adj…

For a stable marginally outer trapped surface (MOTS) in an axially symmetric spacetime with cosmological constant $Λ> 0$ and with matter satisfying the dominant energy condition, we prove that the area $A$ and the angular momentum $J$ satisfy the inequality $8π|J| \le A\sqrt{(1-ΛA/4π)(1-ΛA/12π)}$ which is saturated pre…

We present a marked analogue of Carter and Saito's movie theorem. Our definition of marking was chosen to coincide with the markings that arise in link Floer homology. In order to deal with complications arising from certain isotopies, we define three equivalence relations for marked surfaces and work over an equivalen…

This study improves annuity pricing by applying state-space Lee-Carter model.

The aim of this paper is to study the construction of prospective mortality tables from a low number of persons subjected to risk. The presented models are the Lee-Carter and log-Poisson methods respectively. The low number of people subjected to risk, particularly noticed for the persons who are getting on, implies th…

Paper introduces skew-symmetric matrices for virtual doodle classification.

The paper constructs minimal realizations of signed Gauss paragraphs using graph theory.

The study examines how different interpolation methods affect the decomposition of life insurance surplus.

Global existence and boundedness proved for quasilinear wave equations on Kerr black holes.

We introduce a new cohomology-theoretic method for classifying generic immersed curves in closed compact surfaces by using Gauss codes. This subsumes a result of J.S. Carter on classifying immersed curves in oriented compact surfaces, and provides a criterion for when an immersion is two-colorable. We note an applicati…

We introduce a new homology theory of quandles, called simplicial quandle homology, which is quite different from quandle homology developed by Carter et al. We construct a homomorphism from a quandle homology group to a simplicial quandle homology group. As an application, we obtain a method for computing the complex …

A new classification theorem for links by the authors and Roger Fenn leads to computable link invariants. As an illustration we distinguish the left and right trefoils and recover the result of Carter et al that the 2-twist-spun trefoil is not isotopic to its orientation reverse. We sketch the proof the classification …

New definitions of rack and quandle modules are introduced, and shown to generalise the definitions previously studied by Andruskiewitsch, Etingof and Grana. This new construct is shown to coincide with Beck's general definition of a module in an arbitrary category. A theory of Abelian extensions of racks and quandles …

Study finds actuarial unfairness in China's pension system, proposing income-dependent annuitization rules.

Extends Khovanov homology to surfaces with singularities.

The aim of this paper is to propose a realistic and operational model to quantify the systematic risk of mortality included in an engagement of retirement. The model presented is built on the basis of model of Lee-Carter. The stochastic prospective tables thus built make it possible to project the evolution of the rand…

For proper subsets U of {1,2,...,31} we define and construct U-regular isotopy invariants of the Carter-Rieger-Saito movies (representing knotted surfaces) and use these to show that there are ambient isotopic knotted surfaces represented by movies M1 and M2 for which movie-moves of type 31 are required to get from M1 …

Clarifies sign ambiguity in Khovanov homology functoriality.

The aim of this paper is to propose a realistic and operational model to quantify the systematic risk of mortality included in an engagement of retirement. The model presented is built on the basis of model of Lee-Carter. The stochastic prospective tables thus built make it possible to project the evolution of the rand…

We introduce the notion of a quandle with a good involution and its homology groups. Carter et al. defined quandle cocycle invariants for oriented links and oriented surface-links. By use of good involutions, quandle cocyle invariants can be defined for links and surface-links which are not necessarily oriented or orie…

Paper develops a two-population model to assess longevity basis risk.

We prove that Morrison and Nieh's categorification of the su(3) quantum knot invariant is functorial with respect to tangle cobordisms. This is in contrast to the categorified su(2) theory, which was not functorial as originally defined. We use methods of Bar-Natan to construct explicit chain maps for each variation of…

The paper finds conditions for pseudosymmetric spacetimes to be perfect fluids.

We consider (flat) Cauchy-complete GH spacetimes, i.e., globally hyperbolic flat lorentzian manifolds admitting some Cauchy hypersurface on which the ambient lorentzian metric restricts as a complete riemannian metric. We define a family of such spacetimes - model spacetimes - including four subfamilies: translation sp…

In the present paper, we construct a simple invariant which provides a sliceness obstruction for {\em free knots}. This obstruction provides a new point of view to the problem of studying cobordisms of curves immersed in 2-surfaces, a problem previously studied by Carter, Turaev, Orr, and others. The obstruction to sli…

Jebsen-Birkhoff theorem extended to Berwald spacetimes.

The paper introduces and analyzes pseudo generalized Ricci-recurrent spacetimes in modified gravity.

We present a grid diagram analogue of Carter, Rieger and Saito's smooth movie theorem. Specifically, we give definitions for grid movies, grid movie isotopies and present a definition of grid planar isotopy as a particular subset of the grid diagram moves: stabilization, destabilization and commutation. We show that gr…

The study characterizes spacetimes with quasi-constant sectional curvature and explores their properties in $\mathcal{F}(\mathcal{R})$-gravity.

The article introduces pseudo generalized Ricci-recurrent spacetimes and their applications in modified gravity.

Study explores geometric properties of Vaidya-Bonner-de Sitter spacetime.

The paper studies the past inextendibility of FLRW spacetimes using the VDR asymptote.

The study characterizes GRW spacetimes with gradient solitons and phantom era.

Characterizes Lorentzian manifolds embeddable in Minkowski spacetime.

New proof shows FLRW spacetimes can't be extended smoothly in certain axisymmetric cases.

Study shows how certain expanding spacetimes can collapse into flat or Kasner spacetimes.

Study of quasilocal mass using isometric embedding in various spacetimes.

Study directed completion of spacetimes, focusing on Schwarzschild spacetime.

Identifies all type D^k spacetimes in arbitrary dimensions.

Characterizes pseudo B-symmetric spacetimes and their implications in f(R) gravity.

Standard static Finsler spacetimes defined and properties studied.

Characterizes a specific type of spacetime using vector fields.

Study maximal hypersurfaces in open spacetimes using a maximum principle.

The paper examines the initial geometry of vacuum cosmological spacetimes and introduces new methods to characterize their behavior.