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Haitao Liu

Publications and source records attributed to Haitao Liu.

53 records · Page 3Linked to original sources
arXiv2016

The distribution of information content in English sentences

Sentence is a basic linguistic unit, however, little is known about how information content is distributed across different positions of a sentence. Based on authentic language data of English, the present study calculated the entropy and other entropy-related statistics for different sentence positions. The statistics indicate a three-step staircase-shaped distribution pattern, with entropy in the initial position lower than the medial positions (positions other than the initial and final), the medial positions lower than the final position and the medial positions showing no significant difference. The results suggest that: (1) the hypotheses of Constant Entropy Rate and Uniform Information Density do not hold for the sentence-medial positions; (2) the context of a word in a sentence should not be simply defined as all the words preceding it in the same sentence; and (3) the contextual information content in a sentence does not accumulate incrementally but follows a pattern of "the whole is greater than the sum of parts".

cs.CL↗
arXiv2015

Dependency length minimization: Puzzles and Promises

In the recent issue of PNAS, Futrell et al. claims that their study of 37 languages gives the first large scale cross-language evidence for Dependency Length Minimization, which is an overstatement that ignores similar previous researches. In addition,this study seems to pay no attention to factors like the uniformity of genres,which weakens the validity of the argument that DLM is universal. Another problem is that this study sets the baseline random language as projective, which fails to truly uncover the difference between natural language and random language, since projectivity is an important feature of many natural languages. Finally, the paper contends an "apparent relationship between head finality and dependency length" despite the lack of an explicit statistical comparison, which renders this conclusion rather hasty and improper.

cs.CL↗
arXiv2015

The influence of Chunking on Dependency Crossing and Distance

This paper hypothesizes that chunking plays important role in reducing dependency distance and dependency crossings. Computer simulations, when compared with natural languages,show that chunking reduces mean dependency distance (MDD) of a linear sequence of nodes (constrained by continuity or projectivity) to that of natural languages. More interestingly, chunking alone brings about less dependency crossings as well, though having failed to reduce them, to such rarity as found in human languages. These results suggest that chunking may play a vital role in the minimization of dependency distance, and a somewhat contributing role in the rarity of dependency crossing. In addition, the results point to a possibility that the rarity of dependency crossings is not a mere side-effect of minimization of dependency distance, but a linguistic phenomenon with its own motivations.

cs.CL↗
arXiv2014

The risks of mixing dependency lengths from sequences of different length

Mixing dependency lengths from sequences of different length is a common practice in language research. However, the empirical distribution of dependency lengths of sentences of the same length differs from that of sentences of varying length and the distribution of dependency lengths depends on sentence length for real sentences and also under the null hypothesis that dependencies connect vertices located in random positions of the sequence. This suggests that certain results, such as the distribution of syntactic dependency lengths mixing dependencies from sentences of varying length, could be a mere consequence of that mixing. Furthermore, differences in the global averages of dependency length (mixing lengths from sentences of varying length) for two different languages do not simply imply a priori that one language optimizes dependency lengths better than the other because those differences could be due to differences in the distribution of sentence lengths and other factors.

cs.CL↗
arXiv2012

An instability of hyperbolic space under the Yang-Mills flow

We consider the Yang-Mills flow on hyperbolic 3-space. The gauge connection is constructed from the frame-field and (not necessarily compatible) spin connection components. The fixed points of this flow include zero Yang-Mills curvature configurations, for which the spin connection has zero torsion and the associated Riemannian geometry is one of constant curvature. Perturbations to the fixed point corresponding to hyperbolic 3-space can be expressed as a linear superposition of distinct modes, some of which are exponentially growing along the flow. The growing modes imply the divergence of the (gauge invariant) perturbative torsion for a wide class of initial data, indicating an instability of the background geometry that we confirm with numeric simulations in the partially compactified case. There are stable modes with zero torsion, but all the unstable modes are torsion-full. This leads us to speculate that the instability is induced by the torsion degrees of freedom present in the Yang-Mills flow.

hep-th↗
arXiv2012

Waves on subwavelength metallic surfaces: a microscopic view point

The electromagnetic properties of subwavelength metallic surfaces are due to two kinds of elementary distinct waves, the famous surface plasmon polariton and the quasi-cylindrical wave, which are both scattered by the subwavelength indentations as they propagate on the metal. The ab-initio microscopic description of the electromagnetic properties starting from the sole knowledge of the elementary waves launched in between the indentation has a long history in grating theories. We review the evolution of the ideas and the fundamental principles that govern these waves and their impacts. For the sake of illustration, the emblematic case of a metal surface perforated by a subwavelength-hole array, which exhibits remarkable transmission properties, is taken to illustrate our purpose.

cond-mat.other↗
arXiv2012

An Amendment of Fast Subspace Tracking Methods

Tuning stepsize between convergence rate and steady state error level or stability is a problem in some subspace tracking schemes. Methods in DPM and OJA class may show sparks in their steady state error sometimes, even with a rather small stepsize. By a study on the schemes' updating formula, it is found that the update only happens in a specific plane but not all the subspace basis. Through an analysis on relationship between the vectors in that plane, an amendment as needed is made on the algorithm routine to fix the problem by constricting the stepsize at every update step. The simulation confirms elimination of the sparks.

math.NA↗
arXiv2011

Structural and electronic properties of ScnOm (n=1~3, m=1~2n) clusters: Theoretical study using screened hybrid density functional theory

The structural and electronic properties of small scandium oxide clusters ScnOm (n = 1 - 3, m = 1 - 2n) are systematically studied within the screened hybrid density functional theory. It is found that the ground states of these scandium oxide clusters can be obtained by the sequential oxidation of small "core" scandium clusters. The fragmentation analysis demonstrates that the ScO, Sc2O2, Sc2O3, Sc3O3, and Sc3O4 clusters are especially stable. Strong hybridizations between O-2p and Sc-3d orbitals are found to be the most significant character around the Fermi level. In comparison with standard density functional theory calculations, we find that the screened hybrid density functional theory can correct the wrong symmetries and yield more precise description for the localized 3d electronic states of scandium.

physics.atm-clus↗
arXiv2011

Octet Quark Contents from SU(3) Flavor Symmetry

With the parametrization of parton distribution functions (PDFs) of the proton by Soffer \textit{et al.}, we extend the valence quark contents to other octet baryons by utilizing SU(3) flavor symmetry. We find the method practically useful. Fragmentation functions (FFs) are further obtained through the phenomenological Gribov-Lipatov relation at the $x \to 1$ region. Our results are compared with different models, and these different predictions can be discriminated by upcoming experiments.

hep-ph↗
arXiv2011

Tomimatsu-Sato geometries, holography and quantum gravity

We analyze the $δ=2$ Tomimatsu-Sato spacetime in the context of the proposed Kerr/CFT correspondence. This 4-dimensional vacuum spacetime is asymptotically flat and has a well-defined ADM mass and angular momentum, but also involves several exotic features including a naked ring singularity, and two disjoint Killing horizons separated by a region with closed timelike curves and a rod-like conical singularity. We demonstrate that the near horizon geometry belongs to a general class of Ricci-flat metrics with $SL(2,\mathbb{R})\times U(1)$ symmetry that includes both the extremal Kerr and extremal Kerr-bolt geometries. We calculate the central charge and temperature for the CFT dual to this spacetime and confirm the Cardy formula reproduces the Bekenstein-Hawking entropy. We find that all of the basic parameters of the dual CFT are most naturally expressed in terms of charges defined intrinsically on the horizon, which are distinct from the ADM charges in this geometry.

hep-th↗
arXiv2011

Refined Wall-Crossing, Free Fermions and Crystal Melting

In this paper, we use an M-theory model to conjecture the refined reminiscence of the OSV formula connecting the refined topological string partition function with the refined BPS states partition function for the toric Calabi-Yau threefolds without any compact four cycles. Further, we show how to use the vertex operators in 2d free fermions to reproduce the refined BPS states partition function for the $\mathbb{C}^3$ case and the wall-crossing formulas of the refined BPS states partition function for the resolved conifold and $\mathcal{O}(-2)\oplus\mathcal{O}\rightarrow \mathbb{P}^1$ cases.

hep-th↗
arXiv2010

Atmospheric Oxygen Binding and Hole Doping in Deformed Graphene on a SiO2 Substrate

Using micro-Raman spectroscopy and scanning tunneling microscopy, we study the relationship between structural distortion and electrical hole doping of graphene on a silicon dioxide substrate. The observed upshift of the Raman G band represents charge doping and not compressive strain. Two independent factors control the doping: (1) the degree of graphene coupling to the substrate, and (2) exposure to oxygen and moisture. Thermal annealing induces a pronounced structural distortion due to close coupling to SiO2 and activates the ability of diatomic oxygen to accept charge from graphene. Gas flow experiments show that dry oxygen reversibly dopes graphene; doping becomes stronger and more irreversible in the presence of moisture and over long periods of time. We propose that oxygen molecular anions are stabilized by water solvation and electrostatic binding to the silicon dioxide surface.

cond-mat.mtrl-sci↗
arXiv2010

Notes On U(1) Instanton Counting On $A_{l-1}$ ALE Spaces

In this note, we investigate the detailed relationship between the orbifold partition counting and the (l-quotient, l-core) pair counting. We show that the orbifold partition counting is exactly the same as the (l-quotient, l-core) pair counting.

hep-th↗
arXiv2010

Matrix Model and Refined Wall-Crossing Formula

In this paper, we show how to get matrix models corresponding to the refined BPS states partition functions of $\mathbb{C}^3$, resolved conifold and $\mathbb{C}^3/\mathbb{Z}_2$ by inserting the identity operator at a proper position in the fermionic expression of the refined BPS states partition functions.

hep-th↗
arXiv2005

Selective adsorption of first-row atoms on boron nitride nanotubes: the effect of localized states

First-principles calculations reveal that the adsorption of representative first-row atoms with different electronegativity, such as lithium (Li), carbon (C) and fluorine (F), on zigzag single-walled boron nitride nanotubes (BNNTs) exhibits surprising selectivity. The adsorption energy and adsorption site are dependent upon the chemical activity of adsorbate with respect to the B and N atoms in the host tube. In detail, the F atom prefers to be adsorbed on the top of the B atom, the C atom is energetically favorable to stay on the bridge site which is perpendicular to the tube-axis, and the Li atom hardly adheres to the tube (an endothermal reaction). The adsorption behavior of these three types of elements on BNNTs is elucidated based on the frontier molecular orbital theory. In addition, the mechanism of modification of electronic structures of BNNTs by adsorption is probed, and a feasible approach is proposed to tailor the electronic properties of BNNTs.

cond-mat.mtrl-sci↗