Theory Of Gap Research Articles

The City in the Country: Wilderness Gentrification and the Rent Gap

In this paper I explore the efficacy of applying Neil Smith's theory of the rent gap to rural gentrification in New York State's Adirondack Park, making three central claims. In the first place, although the underlying impetus for both rural and urban gentrification (namely, the maximization of profit on the part of a variety of gentrifying agents from individual owner-occupants to large-scale developers) is essentially the same, some fundamental differences between the determination of what constitutes ‘undercapitalized’ ground rent in the city and the wilderness leads to subsequent differences in the geographical expression of gentrification in each area. In the second, the unique land-management practices instituted by the State of New York in this region have set up the conditions for a singular type of disinvestment not typically found in the city, rendering disinvestment a central aspect of Adirondack gentrification but in a different way than the disinvestment which anchors Smith's argument. Finally, I argue that the ‘postproductivist’ theories which have recently gained currency in the extant rural gentrification literature are not applicable to the empirical realities of Adirondack land use, suggesting that rural areas themselves may be sufficiently differentiated to render the idea of an overarching, homogeneous ‘rural gentrification’ suspect and pointing to the need for a more refined and specific set of labels to indicate a variety of landscape-specific gentrification models in the hinterlands.

A Quantitative Theory of the Gender Gap in Wages

Using panel data from the National Longitudinal Survey of Youth (NLSY), we document that gender differences in wages almost double during the first 20 years of labor market experience and that there are substantial gender differences in employment and hours of work during the life cycle. A large portion of gender differences in labor market attachment can be traced to the impact of children on the labor supply of women. We develop a quantitative life-cycle model of fertility, labor supply, and human capital accumulation decisions. We use this model to assess the role of fertility on gender differences in labor supply and wages over the life cycle. In our model, fertility lowers the lifetime intensity of market activity, reducing the incentives for human capital accumulation and wage growth over the life cycle of females relative to males. We calibrate the model to panel data of men and to fertility and child related labor market histories of women. We find that fertility accounts for most of the gender differences in labor supply and wages during the life cycle documented in the NLSY data.

Understanding the Gender Gap in Small Business Success

The authors explore how urban versus rural community location shapes the extent to which various individual, relational, and structural factors affect the gender gap in small business success. Building on previous research on gender and small business success, gender queuing theories, and gendered organization/institution theories, they develop a place-specific theory of the gender gap in small business success. The findings, based on small business data collected in urban and rural Iowa (1995 and 1997), support queuing arguments and raise questions about the effectiveness of crowded-sector explanations. They indicate that the gender gap in small business success operates such that men-owned businesses are more successful in both urban and rural settings but that men-owned businesses are even more successful than women-owned businesses in urban than rural communities. The authors discuss the causes and consequences of the gender gap in small business success in rural and urban places and identify key issues for further research.

Theory of the Hybridization Gap in Ce Compounds with Crystalline Electric Field Splitting

We invastigate the general properties of the hybridization gap in Ce compounds focusing on the case with orthorhombic structure. In the study we use the periodic Anderson model possessing Kramers doublets in f level and mainly discuss the hybridization between one of Kramers doublets and a conduction band. In higher symmetry such as cubic, tetragonal and hexagonal structure, the f-state with J z = ±1/2 component becomes insulating state with a real energy gap near the f-level. In lower symmetry such as orthorhombic structure, although f-states contain the component of J z = ±1/2, semimetallic states with pseudogap or metallic states with a peak are realized in specific f states.

The Developmental Theory of the Gender Gap: Women’s and Men’s Voting Behavior in Global Perspective

Studies carried out in many countries in previous decades found that women were more conservative than men and less likely to participate in politics. Here, it is examined whether this traditional gender gap persists today, or whether gender cleavages in the electorate have converged, and whether the phenomenon of the modern gender gap, with women more left wing, has become evident elsewhere. The article draws on evidence from the World Values Surveys in the early 1980s, and the early and mid-1990s carried out in over sixty countries around the world. This study establishes that gender differences in electoral behavior have been realigning, with women moving toward the left of men throughout advanced industrial societies (though not in postcommunist societies or developing countries) and explores the reasons for this development, including the role of structural and cultural factors. The conclusion considers the political implications of the findings.

Theory of the spin gap in high-temperature superconductors.

We analyze pairing in two dimensional spin liquids. We argue that interplane pairing enhanced by magnetic correlations is the most plausible explanation of the spin gap phenomenon observed in underdoped cuprates. The details of the pairing theory depend on the in-plane antiferromagnetic correlations. We consider two models: $2p_F$ correlations induced by a strong gauge field interaction and undamped spin waves. We estimate the pairing temperature $T_s$ and the angular dependence of the gap function and discuss physical consequences.

The Rent Gap and Transformation of the Built Environment: Case Studies in Malmö 1860–1985

ABSTRACTThe theory of rent gap has received much attention in the 1980's literature on gentrification and urban renewal. Two shortcomings in this literature are the neglect of other formulations than Neil Smith's and the lack of empirical research efforts to put the theory to a test. This paper attempts to alleviate these shortcomings by first presenting a comparison of alternative formulations of rent gap theory, and then presenting the results of an empirical effort to test the theory with historical data on six areas in Malmo, Sweden. These results corroborate the theory, but suggest some modifications.

On the Many Body Theory of the Energy Gap in Semiconductors

We compare a variety of approximation schemes, all predicting the excitation structure of a semiconductor. All schemes are placed within one common framework, in which the electron self energy is the central quantity. In arriving at this self energy it turns out to be essential to screen the Coulomb interaction between electrons both statically and dynamically. We subsequently discuss the Hartree, Hartree-Fock, local density functional and Slater Xα schemes, which all lead to incorrect excitation structures, and the GW scheme of Hedin which, in view of recent successes, appears to be a very promising scheme.

A perturbation theory of the miscibility gap in metal-salt solutions

The metal-salt solutions are regarded as being composed of N1 positive ions of charge Z1e and N2 negative ions of charge Z2e in a volume Ω; the corresponding number densities and concentrations are defined as p α = Nα/Ω and xα=Nα/N (α=1,2), with N=N1+N2. The excess of positive charge is compensated by the conduction electrons which are assumed to provide a rigid, uniform background of charge density ep o, ensuring overall charge neutrality: $$ {\rho _1}{z_1} + {\rho _2}{z_2} + {\rho _{\rm{o}}} = 0 $$ (1) This reference system will serve as a starting point for our perturbation expansion. In that case the ions are assumed to interact via the following potential: $$ {{\rm{U}}_{\alpha \beta }}({\rm{r}}) = {{{{\rm{z}}_\alpha }{{\rm{z}}_\beta }{{\rm{e}}^2}} \over {\rm{r}}} + (1 - {\delta _{\alpha \beta }}){{\rm{V}}_{\rm{o}}}({\rm{r}}) $$ (2a) where the short range repulsion, which acts only between oppositely charged ions, is taken to be of exponential form: $$ {{\rm{V}}_{\rm{o}}}({\rm{r}}) = {{\rm{A}}_{{\rm{12}}}}\exp ( - {\alpha _{12}}{\rm{r}}) $$ (2b) The potential (2) is a simplified version of the usual Born-Huggins-Mayer potential, retaining only its essential features. We have dropped the Van der Waals dispersion terms, as well as the short range repulsion between equally charged ions, since the Coulomb repulsion is sufficiently strong to keep them apart. The limiting situations of the potential (2) are: i) x-1, i.e. the pure metal, for which we recover the one component plasma (O.C.P.) model3,4; ii) x=0, i.e. the pure salt, reasonably well described by a Born-Huggins-Mayer rigid ion potential, provided ion polarizability effects are not too important.5 The pair correlation functions are calculated through the closed set of equations composed of the Qrnstein-Zernicke relation and the hypernetted-chain (H.N.C.) equations.2

Density-functional theory of the band gap.

There is a correction to the energy band gap obtained from the eigenvalues of the exact one-electron density-functional equation due to the discontinuity in the exchange-correlation potential in an insulator. This correction is expressed in terms of the electron self-energy. If the local-density approximation is used for the exchange-correlation potential, then an additional correction to the gap is needed. Both terms are evaluated for a two-plane-wave model with exchange only. Empirical evidence is also given for the discontinuity.

Relativistic and core-relaxation effects on the energy bands of gallium arsenide and germanium.

Relativistic self-consistent band-structure calculations using either norm-conserving pseudopotentials or the linear-muffin-tin-orbital method (LMTO) demonstrate that relativistic effects on some conduction bands of gallium arsenide, if qualitatively not unexpected, are however, surprisingly large (the direct gap is reduced by one-half), despite the relatively light atoms. This is discussed in terms of a simple bonding-antibonding picture: Relativistic effects may either be depressed or amplified, with respect to free atoms, by the formation of bands and bonds. The gallium 3d core states are known to be shallow, i.e., not far enough from the 4s and 4p energies to allow them to be treated as completely frozen-core states. Therefore, in a new self-consistent LMTO calculation we treat them on the same footing as the other valence-band states. The most evident effects of the Ga 3d core-relaxation are a further, sizable shrinkage of the gaps, and a clear improved agreement of the valence bands with photoemission experiments. We stress the influence of relativistic and core-relaxation effects on the bands of GaAs, and also show, for the first time, that the intrinsic failure of the local-density approximation as far as gaps are concerned is much larger for third-row semiconductors than for, e.g., the better-known case of Si. This is emphasized by our calculation for the neighboring elemental semiconductor, germanium, where almost no gap is found, i.e., metallization has occurred one row too early. The calculated gaps are a necessary reference for the development of the density-functional theory of the energy gap.

Density-Functional Theory of the Energy Gap

The energy-band gap of an insulator is obtained from the eigenvalues of the one-particle density-functional equation for the ground state and a finite correction due to the discontinuity of the functional derivative of the exchange and correlation energy. This correction is expressed in terms of the improper self-energy and the density-functional exchange-correlation potential. It is evaluated for a two-plane-wave model including exchange only.

Microscopic theory of the average band gap of semiconductors

AbstractIn Phillips' spectroscopic theory of semiconductors, the covalency and ionicity are derived empirically from the average band gap between the highest valence and lowest conduction bands. In this paper an explicit expression for the average band gap is derived based on a continued fraction representation of the polarizability matrix. Results of a calculation for six covalent and polar semiconductors, using the pseudopotential model, are presented and compare favorably with experimental values.

Theory of the Anisotropic Energy Gap in Superconducting Lead

The energy gap of a model anisotropic superconductor is considered. This model calculation forms the basis of a more realistic theoretical consideration of the energy gap of superconducting Pb, one in which the phonon density of states is the principal source of gap anisotropy. The effect of energy-band structure, important only near Brillouin-zone boundaries, is included as a perturbation. The phonon density of states is calculated from the experimental dispersion curves and singularities---present in the special density of states entering the superconductivity problem---are discussed. The phonon density of states and the isotropic gap solution obtained by previous workers are used to calculate the anisotropic part of the energy gap. The double gap, $2\ensuremath{\Delta}$, is found to have an absolute maximum of 2.86 meV in the [100] direction, and an absolute minimum of 2.55 meV in the [110] direction. Ten other maxima, minima, and saddle points are listed. The effect of the energy-gap anisotropy on electron-tunneling, electromagnetic-absorption, and acoustic-attenuation experiments is predicted.