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arXiv research

A locally-built, LLM-digested index of recent arXiv papers in quant finance, geometry/topology, and statistical ML — keyword search served straight from SQLite on this machine.

168,742 papers · 148 categories

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48 results for Zhengxu He

Mini-Hes improves LFA model performance on HDI tasks with missing data.

problem Effective representation of high-dimensional, incomplete data for user behavior understanding.
method Proposes Mini-Hes, a parallelizable second-order LFA model using mini-block diagonal Hessian-free optimization.
result Mini-Hes outperforms state-of-the-art models in missing data estimation tasks on recommender system datasets.

A Bayesian agent learns about the structure of a stationary process from ob- serving past outcomes. We prove that his predictions about the near future become ap- proximately those he would have made if he knew the long run empirical frequencies of the process.

2014-06-25abs ↗pdf ↗

A hybrid model combines BPH and HE distributions for better heavy-tailed distribution approximation.

problem Accurate modeling of heavy-tailed distributions in various applications.
method A hybrid model of Bernstein phase-type and hyperexponential distributions with optimized parameters.
result Significant improvement in capturing both body and tail of heavy-tailed distributions.

We review some ideas of Grothendieck and others on actions of the absolute Galois group Γ Q of Q (the automorphism group of the tower of finite extensions of Q), related to the geometry and topology of surfaces (mapping class groups, Teichm{ü}ller spaces and moduli spaces of Riemann surfaces). Grothendieck's motivation…

2016-03-10abs ↗pdf ↗

In this paper we consider a modification of the classical Merton portfolio optimization problem. Namely, an investor can trade in financial asset and consume his capital. He is additionally endowed with a one unit of an indivisible asset which he can sell at any time. We give a numerical example of calculating the opti…

2014-03-13abs ↗pdf ↗

The paper proves rigidity and uniformization theorems for infinite circle patterns and convex polyhedra in hyperbolic 3-space.

problem Characterize infinite circle patterns and convex polyhedra in hyperbolic 3-space.
method Extends techniques from previous work to prove rigidity and uniformization theorems for infinite circle patterns and convex polyhedra.
result Establishes existence and rigidity of infinite regular circle patterns and convex trivalent polyhedra.

In this paper, the author considers the numerical computation of CVA for large systems by Mote Carlo methods. He introduces two types of stochastic mesh methods for the computations of CVA. In the first method, stochastic mesh method is used to obtain the future value of the derivative contracts. In the second method, …

2015-10-15abs ↗pdf ↗

In 2003, S.-s. Chern began a study of almost-complex structures on the 6-sphere, with the idea of exploiting the special properties of its well-known almost-complex structure invariant under the exceptional group G2G_2. While he did not solve the (currently still open) problem of determining whether there exists an int…

2014-05-14abs ↗pdf ↗

Characterizes infinite ideal polyhedra in hyperbolic 3-space and proves their existence and rigidity.

problem Characterize infinite ideal polyhedra in hyperbolic 3-space.
method Study ideal circle patterns (ICPs) and develop a uniform Ring Lemma via pointed Gromov-Hausdorff convergence.
result Establish existence and rigidity of embedded ICPs and infinite ideal polyhedra (IIP).

Study the geometry and symmetries of moduli spaces of connections on KT manifolds.

problem Investigate the geometry and symmetries of moduli spaces of Hermitian-Einstein and instanton connections on KT manifolds.
method Analyze the geometry and symmetries of moduli spaces of Hermitian-Einstein and instanton connections on KT manifolds, using vector fields and connections with skew-symmetric torsion.
result The geometry of moduli spaces can be modeled on principal bundles with specific fibre and base spaces.

A continuous-time consumption-investment model with constraint is considered for a small investor whose decisions are the consumption rate and the allocation of wealth to a risk-free and a risky asset with logarithmic Brownian motion fluctuations. The consumption rate is subject to an upper bound constraint which linea…

2014-04-30abs ↗pdf ↗

In [Duke Math. J. 101 (1999) 359-426], Mikhail Khovanov constructed a homology theory for oriented links, whose graded Euler characteristic is the Jones polynomial. He also explained how every link cobordism between two links induces a homomorphism between their homology groups, and he conjectured the invariance (up to…

2002-06-28abs ↗pdf ↗

Improved optimal regularity for harmonic almost complex structures.

problem Establishing optimal regularity for harmonic almost complex structures.
method Quantitative stratification method and rectifiability of singular strata.
result Optimal regularity theory for energy minimizing harmonic almost complex structures.

We introduce a notion of Gieseker stability for a filtered holomorphic vector bundle FF over a projective manifold. We relate it to an analytic condition in terms of hermitian metrics on FF coming from a construction of the Geometric Invariant Theory (G.I.T). These metrics are balanced in the sense of S.K. Donaldson.…

2006-01-19abs ↗pdf ↗

Two classes of gamma-ray bursts (GRBs), short and long, have been determined without any doubts, and are usually ascribed to different progenitors, yet these classes overlap for a variety of descriptive parameters. A subsample of 46 long and 22 short FermiFermi GRBs with estimated Hurst Exponents (HEs), complemented by mi…

2015-07-17abs ↗pdf ↗

Tissot's indicatrix theory is foundational for quasiconformal mappings.

problem Understanding map distortions in geographical projections.
method Mathematical analysis of map projections and their distortions.
result Tissot's work laid the groundwork for quasiconformal mappings.

The paper proves existence of solutions to Kazdan-Warner equations on finite graphs.

problem Existence of solutions to Kazdan-Warner equations on finite graphs.
method Variational methods and eigenvalue analysis.
result The paper proves the existence of solutions to the Kazdan-Warner equations under various conditions.

We give a twistorial interpretation of geometric structures on a Riemannian manifold, as sections of homogeneous fibre bundles, following an original insight by Wood (2003). The natural Dirichlet energy induces an abstract harmonicity condition, which gives rise to a geometric gradient flow. We establish a number of an…

2019-07-13abs ↗pdf ↗

For a 3-manifold M, McMullen derived from the Alexander polynomial of M a norm on H^1(M, R) called the Alexander norm. He showed that the Thurston norm on H^1(M, R), which measures the complexity of a dual surface, is an upper bound for the Alexander norm. He asked if these two norms were equal on all of H^1(M,R) when …

1999-08-11abs ↗pdf ↗

This paper formalizes manifolds in positive characteristic varieties.

problem Establishing l-adic formal manifold structures on positive characteristic varieties.
method Develops and proves the existence of l-adic formal manifold structures and abelianized Galois symmetries.
result Proves l-adic homotopic equivalence and l-local lifting for simply-connected varieties.

Donoho's JCGS (in press) paper is a spirited call to action for statisticians, who he points out are losing ground in the field of data science by refusing to accept that data science is its own domain. (Or, at least, a domain that is becoming distinctly defined.) He calls on writings by John Tukey, Bill Cleveland, and…

2017-10-24abs ↗pdf ↗

The moduli space of Hermitian-Einstein connections on certain manifolds has a strong Kähler with torsion structure.

problem Characterizing the moduli space of Hermitian-Einstein connections on manifolds with a dilaton field.
method Demonstrates the existence of a strong Kähler with torsion structure on the moduli space under specific conditions on the Lee form and dilaton field.
result The moduli space admits an induced holomorphic and Killing vector field when the manifold has a holomorphic and Killing vector field invariant under the dilaton.

We consider an adversarial online learning setting where a decision maker can choose an action in every stage of the game. In addition to observing the reward of the chosen action, the decision maker gets side observations on the reward he would have obtained had he chosen some of the other actions. The observation str…

2011-06-13abs ↗pdf ↗

Consider an agent who enters a financial market on day t = 0 with an initial capital amount x. He invests this amount on stocks and the money market, and by day t = T, has generated a wealth W . He is given a convex class of probability measures (called scenarios) and a real-valued function (or floors) corresponding to…

2006-01-25abs ↗pdf ↗

In his book Mickelsson notices that the infinite-dimensional Grassmannian manifold of Segal and Wilson admits a Spin^c structure and after this he naturally considers the problem of defining a Dirac operator on it. Mickelsson gives a possible candidate for such an operator but unfortunately it proves out to be badly di…

2009-09-07abs ↗pdf ↗

Freedman, He, and Wang, conjectured in 1994 that the Mobius energy should be minimized, among the class of all nontrivial links in Euclidean space, by the stereographic projection of the standard Hopf link. We prove this conjecture using the min-max theory of minimal surfaces.

2012-05-03abs ↗pdf ↗