Why has home ownership fallen among the young?

We document that home ownership of households with 'heads' aged 25-44 years fell substantially between 1980 and 2000 and recovered only partially during the 2001-2005 housing boom. The 1980-2000 decline in young home ownership occurred as improvements in mortgage opportunities made it easier to purchase a home. This paper uses an equilibrium life-cycle model calibrated to micro and macro evidence to understand why young home ownership fell over a period when it became easier to own a home. Our findings indicate that a trend toward marrying later and the increase in household earnings risk that occurred after 1980 account for 3/5 to 4/5 of the decline in young home ownership.Housing, home ownership, tenure choice, first-time home-buyers, marriage, income risk

Why has home ownership fallen among the young?

We document that home ownership of households with "heads" aged 25 - 44 years fell substantially between 1980 and 2000 and recovered only partially during the 2001-2005 housing boom. The 1980-2000 decline in young home ownership occurred as improvements in mortgage opportunities made it easier to purchase a home. This paper uses an equilibrium life-cycle model calibrated to micro and macro evidence to understand why young home ownership fell over a period when it became easier to own a home. Our findings indicate that a trend toward marrying later and the increase in household earnings risk that occurred after 1980 account for 3/5 to 4/5 of the decline in young home ownership.Home ownership ; Marriage

First-time home buyers and residential investment volatility

Like other macroeconomic variables, residential investment has become much less volatile since the mid-1980s (recent experience notwithstanding.) This paper explores the role of structural change in this decline. Since the early 1980s there have been many changes in the underlying structure of the economy, including those in the mortgage market which have made it easier to acquire a home. We examine how these changes affect residential investment volatility in a life-cycle model consistent with micro evidence on housing choices. We find that a decline in the rate of household formation, increased delay in marriage, and an increase in the cross-sectional variance of earnings drive the decline in volatility. Our findings provide support for the view that the “Great Moderation” in aggregate fluctuations is not just due to smaller aggregate shocks, but is driven at least in part by structural change.Home ownership ; Mortgages

A near zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy

We present a spectroscopic survey of the newly-discovered Canes Venatici dwarf galaxy using the Keck/DEIMOS spectrograph. Two stellar populations of distinct kinematics are found to be present in this galaxy: an extended, metal-poor component, of half-light radius 7'.8(+2.4/-2.1), which has a velocity dispersion of 13.9(+3.2/-2.5) km/s, and a more concentrated (half-light radius 3'.6(+1.1/-0.8) metal-rich component of extremely low velocity dispersion. At 99% confidence, the upper limit to the central velocity dispersion of the metal-rich population is 1.9 km/s. This is the lowest velocity dispersion ever measured in a galaxy. We perform a Jeans analysis on the two components, and find that the dynamics of the structures can only be consistent if we adopt extreme (and unlikely) values for the scale length and velocity dispersion of the metal-poor population. With a larger radial velocity sample and improved measurements of the density profile of the two populations, we anticipate that it will be possible to place strong constraints on the central distribution of the dark matter in this galaxy.Comment: 5 pages, 7 figures, accepted by MNRA

Positive noise cross-correlations in superconducting hybrids: Roles of interfaces and interactions

Shot noise cross-correlations in normal metal-superconductor-normal metal structures are discussed at arbitrary interface transparencies using both the scattering approach of Blonder, Tinkham and Klapwik and a microscopic Green's function approach. Surprisingly, negative crossed conductance in such set-ups [R. Melin and D. Feinberg, Phys. Rev. B 70, 174509 (2004)] does not preclude the possibility of positive noise cross-correlations for almost transparent contacts. We conclude with a phenomenological discussion of interactions in the one dimensional leads connected to the superconductor, which induce sign changes in the noise cross-correlations.Comment: 15 pages, 9 figure

Interface-mediated interactions: Entropic forces of curved membranes

Particles embedded in a fluctuating interface experience forces and torques mediated by the deformations and by the thermal fluctuations of the medium. Considering a system of two cylinders bound to a fluid membrane we show that the entropic contribution enhances the curvature-mediated repulsion between the two cylinders. This is contrary to the usual attractive Casimir force in the absence of curvature-mediated interactions. For a large distance between the cylinders, we retrieve the renormalization of the surface tension of a flat membrane due to thermal fluctuations.Comment: 11 pages, 5 figures; final version, as appeared in Phys. Rev.

A disk census for the nearest group of young stars: Mid-infrared observations of the TW Hydrae Association

A group of young, active stars in the vicinity of TW Hydrae has recently been identified as a possible physical association with a common origin. Given its proximity ($\sim$50 pc), age ($\sim$10 Myr) and abundance of binary systems, the TW Hya Association is ideally suited to studies of diversity and evolution of circumstellar disks. Here we present mid-infrared observations of 15 candidate members of the group, 11 of which have no previous flux measurements at wavelengths longer than 2$\mu$m. We report the discovery of a possible 10$\mu$m excess in CD -33$^{\circ}$7795, which may be due to a circumstellar disk or a faint, as yet undetected binary companion. Of the other stars, only TW Hya, HD 98800, Hen 3-600A, and HR 4796A -- all of which were detected by IRAS -- show excess thermal emission. Our 10$\mu$m flux measurements for the remaining members of the Association are consistent with photospheric emission, allowing us to rule out dusty inner disks. In light of these findings, we discuss the origin and age of the TW Hya Association as well as implications for disk evolution timescales.Comment: 10 pages and 1 PostScript figure, accepted for publication in The Astrophysical Journal Letter

Distribution of partition function zeros of the ±J\pm J model on the Bethe lattice

The distribution of partition function zeros is studied for the $\pm J$ model of spin glasses on the Bethe lattice. We find a relation between the distribution of complex cavity fields and the density of zeros, which enables us to obtain the density of zeros for the infinite system size by using the cavity method. The phase boundaries thus derived from the location of the zeros are consistent with the results of direct analytical calculations. This is the first example in which the spin glass transition is related to the distribution of zeros directly in the thermodynamical limit. We clarify how the spin glass transition is characterized by the zeros of the partition function. It is also shown that in the spin glass phase a continuous distribution of singularities touches the axes of real field and temperature.Comment: 23 pages, 12 figure

Spin and link overlaps in 3-dimensional spin glasses

Excitations of three-dimensional spin glasses are computed numerically. We find that one can flip a finite fraction of an LxLxL lattice with an O(1) energy cost, confirming the mean field picture of a non-trivial spin overlap distribution P(q). These low energy excitations are not domain-wall-like, rather they are topologically non-trivial and they reach out to the boundaries of the lattice. Their surface to volume ratios decrease as L increases and may asymptotically go to zero. If so, link and window overlaps between the ground state and these excited states become ``trivial''.Comment: Extra fits comparing TNT to mean field, summarized in a tabl

Electron injection in a nanotube with leads: finite frequency noise-correlations and anomalous charges

The non-equilibrium transport properties of a carbon nanotube which is connected to Fermi liquid leads, where electrons are injected in the bulk, are computed. A previous work which considered an infinite nanotube showed that the zero frequency noise correlations, measured at opposite ends of the nanotube, could be used to extract the anomalous charges of the chiral excitations which propagate in the nanotube. Here, the presence of the leads have the effect that such-noise cross-correlations vanish at zero frequency. Nevertheless, information concerning the anomalous charges can be recovered when considering the spectral density of noise correlations at finite frequencies, which is computed perturbatively in the tunneling amplitude. The spectrum of the noise cross-correlations is shown to depend crucially on the ratio of the time of flight of quasiparticles traveling in the nanotube to the ``voltage'' time which defines the width of the quasiparticle wave-packets injected when an electron tunnels. Potential applications toward the measurement of such anomalous charges in non-chiral Luttinger liquids (nanotubes or semiconductor quantum wires) are discussed.Comment: 11 pages, 5 figure