Zeeman and Orbital Limiting Fields: Separated Spin and Charge Degrees of Freedom in Cuprate Superconductors

Recent in-plane thermal (Nernst) and interlayer (tunnelling) transport experiments in Bi$_2$Sr$_2$CaCu$_2$O$_{8+y}$ high temperature superconductors report hugely different limiting magnetic fields. Based on pairing (and the uncertainty principle) combined with the definitions of the Zeeman energy and the magnetic length, we show that in the underdoped regime both fields convert to the same (normal state) pseudogap energy scale $T^*$ upon transformation as orbital and spin (Zeeman) critical fields, respectively. We reconcile these seemingly disparate findings invoking separated spin and charge degrees of freedom residing in different regions of a truncated Fermi surface.Comment: 4 pages, 3 figures; accepted for publication in Phys. Rev. B (Rapid Comm.

Thermodynamic identities and particle number fluctuations in weakly interacting Bose--Einstein condensates

We derive exact thermodynamic identities relating the average number of condensed atoms and the root-mean-square fluctuations determined in different statistical ensembles for the weakly interacting Bose gas confined in a box. This is achieved by introducing the concept of {\it auxiliary partition functions} for model Hamiltonians that do conserve the total number of particles. Exploiting such thermodynamic identities, we provide the first, completely analytical prediction of the microcanonical particle number fluctuations in the weakly interacting Bose gas. Such fluctuations, as a function of the volume V of the box are found to behave normally, at variance with the anomalous scaling behavior V^{4/3} of the fluctuations in the ideal Bose gas.Comment: 5 pages, 1 figur

Combined visible and near-infrared OPA for wavelength scaling experiments in strong-field physics

We report the operation of an optical parametric amplifier (OPA) capable of producing gigawatt peak-power laser pulses with tunable wavelength in either the visible or near-infrared spectrum. The OPA has two distinct operation modes (i) generation of >350 uJ, sub 100 fs pulses, tunable between 1250 - 1550 nm; (ii) generation of >190 uJ, sub 150 fs pulses tunable between 490 - 530 nm. We have recorded high-order harmonic spectra over a wide range of driving wavelengths. This flexible source of femtosecond pulses presents a useful tool for exploring the wavelength-dependence of strong-field phenomena, in both the multi-photon and tunnel ionization regimes.Comment: 14 pages, 9 figures, This paper was published in Proceedings of SPIE 10088, Nonlinear Frequency Generation and Conversion: Materials and Devices XVI, doi 10.1117/12.225077

Local Moment Formation in the Superconducting State of a Doped Mott Insulator

A microscopic theory is presented for the local moment formation near a non-magnetic impurity or a copper defect in high-T_c superconductors. We use a renormalized meanfield theory of the t-J model for a doped Mott insulator and study the fully self-consistent, spatially unrestricted solutions of the d-wave superconducting (SC) state in both the spin S=0 and S=1/2 sectors. We find a transition from the singlet d-wave SC state to a spin doublet SC state when the renormalized exchange coupling exceeds a doping dependent critical value. The induced S=1/2 moment is staggered and localized around the impurity. It arises from the binding of an S=1/2 nodal quasiparticle excitation to the impurity. The local density of states spectrum is calculated and connections to NMR and STM experiments are discussed.Comment: 4 pages, 3 figures, revised version, to be published in Phys. Rev. Let

The Participant Effects of Private School Vouchers Across the Globe: A Meta-Analytic and Systematic Review

School voucher programs (a.k.a. opportunity scholarships) are scholarship programs - frequently government funded - that pay for students to attend private schools of their choice. Many private school vouchers programs have been initiated around the world with the goal of increasing the academic performance of students. Voucher programs are often viewed as a way to increase achievement and satisfaction for individual students and families, while at the same time creating competitive pressures that encourage other schools in the area to improve. Countries like Chile and India have developed extensive school voucher programs. While many studies have been conducted on school vouchers, a meta-analysis of the international randomized controlled trials (RCTs) evaluating the achievement effects of vouchers has never been conducted. This study is a meta-analytic consolidation of the evidence from all RCTs evaluating the participant test score effects of school vouchers internationally. Our search process turned up 9,443 potential studies, 19 of which ultimately were included. These 19 studies represent 11 different voucher programs. A total of 262 effect sizes are included, with a two-stage consolidation of those estimates yielding a total of 44 drawn from the last year of the studies. We have included only math and reading outcomes as other subjects are rarely reported and are difficult to compare across countries. We also differentiate between English and reading outcomes and present English results as a subcomponent of the reading effects to account for the effect of local language in the international context. Our meta-analysis indicates overall positive and statistically significant achievement effects of school vouchers that vary by subject (math or reading), location (US v. non-US), and funding type (public or private). Generally, the impacts are larger (1) for reading than for math, (2) for programs outside the US relative to those within the US, and (3) for publicly-funded programs relative to privately-funded programs

Quantum Effects in Black Hole Interiors

The Weyl curvature inside a black hole formed in a generic collapse grows, classically without bound, near to the inner horizon, due to partial absorption and blueshifting of the radiative tail of the collapse. Using a spherical model, we examine how this growth is modified by quantum effects of conformally coupled massless fields.Comment: 13 pages, 1 figure (not included), RevTe

AdviSync: A Dynamic Academic Course Scheduler

Academic advising at universities can be a tedious and disorganized process for both students and advisors. Each advisor may have several dozen advisees to manage each semester, and each individual student has unique sets of classes they need to take to graduate. This might lead to scheduling errors. These errors can put the student behind in their degree, thus extending the time it takes for them to graduate past financial aid periods and delay their entry into the workforce. To address this issue, we create AdviSync. It is a tool for both students and advisors that aims to provide a personalized degree map. AdviSync dynamically suggests classes for each semester left in their degree plan. This application would not only be beneficial for the students to graduate on time, but also eliminate any human error and help with financial repercussions

Perturbed disks get shocked. Binary black hole merger effects on accretion disks

The merger process of a binary black hole system can have a strong impact on a circumbinary disk. In the present work we study the effect of both central mass reduction (due to the energy loss through gravitational waves) and a possible black hole recoil (due to asymmetric emission of gravitational radiation). For the mass reduction case and recoil directed along the disk's angular momentum, oscillations are induced in the disk which then modulate the internal energy and bremsstrahlung luminosities. On the other hand, when the recoil direction has a component orthogonal to the disk's angular momentum, the disk's dynamics are strongly impacted, giving rise to relativistic shocks. The shock heating leaves its signature in our proxies for radiation, the total internal energy and bremsstrahlung luminosity. Interestingly, for cases where the kick velocity is below the smallest orbital velocity in the disk (a likely scenario in real AGN), we observe a common, characteristic pattern in the internal energy of the disk. Variations in kick velocity simply provide a phase offset in the characteristic pattern implying that observations of such a signature could yield a measure of the kick velocity through electromagnetic signals alone.Comment: 10 pages, 13 figures. v2: Minor changes, version to be published in PR