Vacuum Structure of Two-Dimensional ϕ4\phi^4 Theory on the Orbifold S1/Z2S^{1}/Z_{2}

We consider the vacuum structure of two-dimensional $\phi^4$ theory on $S^{1}/Z_{2}$ both in the bosonic and the supersymmetric cases. When the size of the orbifold is varied, a phase transition occurs at $L_{c}=2\pi/m$, where $m$ is the mass of $\phi$. For $L<L_{c}$, there is a unique vacuum, while for $L>L_{c}$, there are two degenerate vacua. We also obtain the 1-loop quantum corrections around these vacuum solutions, exactly in the case of $L<L_{c}$ and perturbatively for $L$ greater than but close to $L_{c}$. Including the fermions we find that the "chiral" zero modes around the fixed points are different for $LL_{c}$. As for the quantum corrections, the fermionic contributions cancel the singular part of the bosonic contributions at L=0. Then the total quantum correction has a minimum at the critical length $L_{c}$.Comment: Revtex, 15 pages, 3 eps figure

The ballistic acceleration of a supercurrent in a superconductor

One of the most primitive but elusive current-voltage (I-V) responses of a superconductor is when its supercurrent grows steadily after a voltage is first applied. The present work employed a measurement system that could simultaneously track and correlate I(t) and V(t) with sub-nanosecond timing accuracy, resulting in the first clear time-domain measurement of this transient phase where the quantum system displays a Newtonian like response. The technique opens doors for the controlled investigation of other time dependent transport phenomena in condensed-matter systems.Comment: 4 pages, 3 figure

Comment on Ds∗→Dsπ0D_s^* \to D_s \pi^0 Decay

We calculate the rate for $D_s^* \rightarrow D_s \pi^0$ decay using Chiral Perturbation Theory. This isospin violating process results from $\pi^0$ - $\eta$ mixing, and its amplitude is proportional to $(m_d - m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr)$. Experimental information on the branching ratio for $D_s^* \rightarrow D_s \pi^0$ can provide insight into the pattern of $SU(3)$ violation in radiative $D^*$ decays.Comment: 7 pages with 2 figures not included but available upon request, CALT-68-191

Modeling the Impacts of Market Activity on Bid-Ask Spreads in the Option Market

In this paper, we examine the impact of market activity on the percentage bid-ask spreads of S&P 100 index options using transactions data. We propose a new market microstructure theory which we call derivative hedge theory, in which option market percentage spreads will be inversely related to the option market maker's ability to hedge his positions in the underlying market, as measured by the liquidity of the latter market. In a perfect hedge world, spreads arise from the illiquidity of the underlying market, rather than from inventory risk or informed trading in the option market itself. We find option market volume is not a significant determinant of option market spreads. This finding leads us to question the use of volume as a measure of liquidity and supports the derivative hedge theory. Option market spreads are positively related to spreads in the underlying market, again supporting our theory. However, option market duration does affect option market spreads, with very slow and very fast option markets both leading to bigger spreads. The fast market result would be predicted by the asymmetric information theory. Inventory model predicts big spreads in slow markets. Neither result would be observed if the underlying securities market provided a perfect hedge. We interpret these mixed results as meaning that the option market maker is able to only imperfectly hedge his positions in the underlying securities market. Our result of insignificant options volume casts doubt on the price discovery argument between stock and option market (Easley, O'Hara, and Srinivas (1998)). Asymmetric information costs in either market are naturally passed to the other market maker's hedgeing and therefore it is unimportant where the informed traders trade.

A Bosonic Analog of a Topological Dirac Semi-Metal: Effective Theory, Neighboring Phases, and Wire Construction

We construct a bosonic analog of a two-dimensional topological Dirac Semi-Metal (DSM). The low-energy description of the most basic 2D DSM model consists of two Dirac cones at positions $\pm\mathbf{k}_0$ in momentum space. The local stability of the Dirac cones is guaranteed by a composite symmetry $Z_2^{\mathcal{TI}}$, where $\mathcal{T}$ is time-reversal and $\mathcal{I}$ is inversion. This model also exhibits interesting time-reversal and inversion symmetry breaking electromagnetic responses. In this work we construct a bosonic version by replacing each Dirac cone with a copy of the $O(4)$ Nonlinear Sigma Model (NLSM) with topological theta term and theta angle $\theta=\pm \pi$. One copy of this NLSM also describes the gapless surface termination of the 3D Bosonic Topological Insulator (BTI). We compute the time-reversal and inversion symmetry breaking electromagnetic responses for our model and show that they are twice the value one gets in the DSM case matching what one might expect from, for example, a bosonic Chern insulator. We also investigate the stability of the BSM model and find that the composite $Z_2^{\mathcal{TI}}$ symmetry again plays an important role. Along the way we clarify many aspects of the surface theory of the BTI including the electromagnetic response, the charges and statistics of vortex excitations, and the stability to symmetry-allowed perturbations. We briefly comment on the relation between the various descriptions of the $O(4)$ NLSM with $\theta=\pi$ used in this paper (a dual vortex description and a description in terms of four massless fermions) and the recently proposed dual description of the BTI surface in terms of $2+1$ dimensional Quantum Electrodynamics with two flavors of fermion ($N=2$ QED$_3$). In a set of four Appendixes we review some of the tools used in the paper, and also derive some of the more technical results.Comment: 33 pages, 4 appendixes, v2: small corrections and added references, v3: new section added (Sec. VI) and additional references. To appear in PR

The Surgical Release of Dupuytren's Contracture Using Multiple Transverse Incisions.

Dupuytren's contracture is a condition commonly encountered by hand surgeons, although it is rare in the Asian population. Various surgical procedures for Dupuytren's contracture have been reported, and the outcomes vary according to the treatment modalities. We report the treatment results of segmental fasciectomies with multiple transverse incisions for patients with Dupuytren's contracture. The cases of seven patients who underwent multiple segmental fasciectomies with multiple transverse incisions for Dupuytren's contracture from 2006 to 2011 were reviewed retrospectively. Multiple transverse incisions to the severe contracture sites were performed initially, and additional incisions to the metacarpophalangeal (MCP) joints, and the proximal interphalangeal (PIP) joints were performed if necessary. Segmental fasciectomies by removing the fibromatous nodules or cords between the incision lines were performed and the wound margins were approximated. The mean range of motion of the involved MCP joints and PIP joints was fully recovered. During the follow-up periods, there was no evidence of recurrence or progression of disease. Multiple transverse incisions for Dupuytren's contracture are technically challenging, and require a high skill level of hand surgeons. However, we achieved excellent correction of contractures with no associated complications. Therefore, segmental fasciectomies with multiple transverse incisions can be a good treatment option for Dupuytren's contracture

Spin dynamics in hole-doped two-dimensional S=1/2 Heisenberg antiferromagnets: ^{63}Cu NQR relaxation in La_{2-x}Sr_xCuO_4 for x≤0.04x\leq 0.04

The effects on the correlated Cu^{2+} S = 1/2 spin dynamics in the paramagnetic phase of La_{2-x}Sr_xCuO_4 (for $x \lesssim 0.04$) due to the injection of holes are studied by means of ^{63}Cu NQR spin-lattice relaxation time T_1 measurements. The results are discussed in the framework of the connection between T_1 and the in-plane magnetic correlation length $\xi_{2D}(x,T)$. It is found that at high temperatures the system remains in the renormalized classical regime, with a spin stiffness constant $\rho_s(x)$ reduced by small doping to an extent larger than the one due to Zn doping. For $x\gtrsim 0.02$ the effect of doping on $\rho_s(x)$ appears to level off. The values for $\rho_s(x)$ derived from T_1 for $T\gtrsim 500$ K are much larger than the ones estimated from the temperature behavior of sublattice magnetization in the ordered phase ($T\leq T_N$). It is argued that these features are consistent with the hypothesis of formation of stripes of microsegregated holes.Comment: 10 pages, 3 figure

Program of analytical and experimental study of porous metal ionizers summary report

Cesium ion emission of porous tungsten material

Requirement for Slit-1 and Robo-2 in zonal segregation of olfactory sensory neuron axons in the main olfactory bulb

The formation of precise stereotypic connections in sensory systems is critical for the ability to detect and process signals from the environment. In the olfactory system, olfactory sensory neurons (OSNs) project axons to spatially defined glomeruli within the olfactory bulb (OB). A spatial relationship exists between the location of OSNs within the olfactory epithelium (OE) and their glomerular targets along the dorsoventral axis in the OB. The molecular mechanisms underlying the zonal segregation of OSN axons along the dorsoventral axis of the OB are poorly understood. Using robo-2/ (roundabout) and slit-1/ mice, we examined the role of the Slit family of axon guidance cues in the targeting of OSN axons during development. We show that a subset of OSN axons that normally project to the dorsal region of the OB mistarget and form glomeruli in the ventral region in robo-2/ and slit-1/ mice. In addition, we show that the Slit receptor, Robo-2, is expressed in OSNs in a high dorsomedial to low ventrolateral gradient across the OE and that Slit-1 and Slit-3 are expressed in the ventral region of the OB. These results indicate that the dorsal-to-ventral segregation of OSN axons are not solely defined by the location of OSNs within the OE but also relies on axon guidance cues