Magnetism and Mott Transition: A Slave-rotor Study

Motivated by the debate of spin-density-wave (SDW) versus local-moment (LM) picture in the iron-based superconducting (FeSC) materials, we consider a two-band orbital-symmetric Hubbard model in which there is robust Fermi surface nesting at $(\pi,0)$. We obtain the phase diagram of such system by a mean-field slave-rotor approach, in which the Fermi surface nesting and the SDW order are explicitly taken into account via a natural separation of scale between the Hund's coupling and the Coulomb interaction. We find that for a sizable range of Hund's coupling the Mott transition acquires a strong first-order character, but there also exists a small range of stronger Hund's coupling in which an enhancement of magnetization can be observed on the SDW side. We interpret the former scenario as one in which a sharp distinction can be drawn between LM and the SDW picture, and the latter scenario as one in which signs of LM physics begin to develop in the metallic phase. It is tempting to suggest that some FeSC materials are in the vicinity of the latter scenario.Comment: 7 pages, 5 figures; v2: Added discussions on anisotropy in renormalized hopping, clarifications and discussions with regard to orbital order, new inset in Fig. 3(d), expanded and revised bibliography, plus other minor revisions. Accepted to PR

The Jalayirids

This book traces the origins, history, and memory of the Jalayirid dynasty, a family that succeeded the Mongol Ilkhans in Iran and Iraq in the 14th and early 15th centuries. The story of how the Jalayirids came to power is illustrative of the political dynamics that shaped much of the Mongol and post-Mongol period in the Middle East. The Jalayirid sultans sought to preserve the social and political order of the Ilkhanate, while claiming that they were the rightful heirs to the rulership of that order. Central to the Jalayirids' claims to the legacy of the Ilkhanate was their attempt to control the Ilkhanid heartland of Azarbayjan and its major city, Tabriz. Control of Azarbayjan meant control of a network of long-distance trade between China and the Latin West, which continued to be a source of economic prosperity through the 8th/14th century

The Jalayirids

This book traces the origins, history, and memory of the Jalayirid dynasty, a family that succeeded the Mongol Ilkhans in Iran and Iraq in the 14th and early 15th centuries. The story of how the Jalayirids came to power is illustrative of the political dynamics that shaped much of the Mongol and post-Mongol period in the Middle East. The Jalayirid sultans sought to preserve the social and political order of the Ilkhanate, while claiming that they were the rightful heirs to the rulership of that order. Central to the Jalayirids' claims to the legacy of the Ilkhanate was their attempt to control the Ilkhanid heartland of Azarbayjan and its major city, Tabriz. Control of Azarbayjan meant control of a network of long-distance trade between China and the Latin West, which continued to be a source of economic prosperity through the 8th/14th century

The Perceptions of Macao Undergraduates Regarding Help Websites for Problem Gambling

This study conducted a web-surfing exercise and a questionnaire survey among a group of Macao undergraduate students regarding the websites that offered help with problem gambling. The results of this study found that most help websites in Macao and Hong Kong provided basic information-sharing service. The students indicated that they would choose their preferred help organization based on factors such as trust, familiarity, and the characteristics of the websites. They also gave comments/suggestions related to the publicity, design, contents, and focus of the websites. This study discussed the results and their implications for future research and practice

Concert recording 2017-09-29

[Track 1]. Qui sedes as dexteram Parris from Gloria / Antonio Vivaldi -- [Track 2]. Pompe vane di mortel!...dove sei from Rodelinda [Track 3]. Di speranza un bel raggio...Venti turbini from Rinaldo / George Frederic Handel -- [Track 4]. An Chloe [Track 5]. Als luise die briefe [Track 6]. Das Veilchen / Wolfgang Amadeus Mozart -- [Track 7]. Mandoline, op. 58, no. 1 [Track 8]. Clair de lune, op. 46, no. 2 / Gabriel Fauré -- [Track 9]. Sympathy [Track 10]. Fantasy in purple / Florence Price -- [Track 11]. Oh, wasn\u27t dat a wide ribber / Harry T. Burleigh -- [Track 12]. There\u27s a man goin\u27 round / Dave Ragland -- [Track 13]. I got a robe / Colin Lett -- [Track 14]. Encor

Raman signature of the U(1) Dirac spin-liquid state in spin-1/2 kagome system

We followed the Shastry--Shraiman formulation of Raman scattering in Hubbard systems and considered the Raman intensity profile in the spin-1/2 "perfect" kagome lattice herbertsmithite ZnCu_3(OH)_6Cl_2, assuming the ground state is well-described by the U(1) Dirac spin-liquid state. In the derivation of the Raman T-matrix, we found that the spin chirality term appears in the A_{2g} channel in the kagome lattice at the t^4/(\omega_i-U)^3 order, but (contrary to the claims by Shastry and Shraiman) vanishes in the square lattice to that order. In the ensuing calculations on the spin-1/2 kagome lattice, we found that the Raman intensity profile in the E_g channel is invariant under an arbitrary rotation in the kagome plane, and that in all (A_{1g}, E_g, and A_{2g}) symmetry channels the Raman intensity profile contains broad continua that display power-law behaviors at low energy, with exponent approximately equal to 1 in the A_{2g} channel and exponent approximately equal to 3 in the E_g and the A_{1g} channels. For the A_{2g} channel, the Raman profile also contains a characteristic 1/\omega singularity, which arose in our model from an excitation of the emergent U(1) gauge field.Comment: 17 pages, 19 figures; Minor revisions, updated to be consistent with the published versio

Associations between physical activity and BMI, body fatness, and visceral adiposity in overweight or obese Latino and non-Latino adults.

Background/objectivesAlthough several studies have reported associations between moderate to vigorous physical activity (MVPA), body fatness and visceral adipose tissue (VAT), the extent to which associations differ among Latinos and non-Latinos remains unclear. This study evaluated the associations between body composition and MVPA in Latino and non-Latino adults.Subjects/methodsAn exploratory, cross-sectional analysis was conducted using baseline data collected from 298 overweight adults enrolled in a 12-month randomized controlled trial that tested the efficacy of text messaging to improve weight loss. MVPA, body fatness and VAT were assessed by waist-worn accelerometry, dual-energy x-ray absorptiometry (DXA), and DXA-derived software (GE CoreScan GE, Madison, WI, USA), respectively. Participants with <5 days of accelerometry data or missing DXA data were excluded; 236 participants had complete data. Multivariable linear regression assessed associations between body composition and MVPA per day, defined as time in MVPA, bouts of MVPA (time per bout ⩾10 min), non-bouts of MVPA (time per bout <10 min) and meeting the 150-min MVPA guideline. The modifying influence of ethnicity was modeled with a multiplicative interaction term.ResultsThe interaction between ethnicity and MVPA in predicting percent body fat was significant (P=0.01, 95% confidence interval (CI) (0.58, 4.43)) such that a given increase in MVPA was associated with a greater decline in total body fat in non-Latinos compared with Latinos (adjusted for age, sex and accelerometer wear time). There was no interaction between ethnicity and MVPA in predicting VAT (g) (P=0.78, 95% CI (-205.74, 273.17)) and body mass index (BMI) (P=0.18, 95% CI (-0.49, 2.26)).ConclusionsAn increase in MVPA was associated with a larger decrease in body fat, but neither BMI nor VAT, in non-Latinos compared with Latinos. This suggests that changes in VAT and BMI in response to MVPA may be less influenced by ethnicity than is total body fatness

Spontaneous spin ordering of Dirac spin liquid in a magnetic field

The Dirac spin liquid was proposed to be the ground state of the spin-1/2 Kagome antiferromagnets. In a magnetic field $B$, we show that the state with Fermi pocket is unstable to the Landau level (LL) state. The LL state breaks the spin rotation around the axis of the magnetic field. We find that the LL state has an in-plane 120$^{\circ}$ $q=0$ magnetization $M$ which scales with the external field $M\sim B^{\alpha}$, where $\alpha$ is an intrinsic calculable universal number of the Dirac spin liquid. We discuss the related experimental implications which can be used to detect the possible Dirac spin liquid phase in Herbertsmithite ZnCu$_3$(OH)$_6$Cl$_2$.Comment: rewritten for clarit

Proposal for detecting spin-chirality terms in Mott insulators via resonant inelastic x-ray scattering

We consider the question of whether resonant inelastic x-ray scattering (RIXS) can be used to detect many-body excitations that are coupled to the spin-chirality terms S_i . (S_j x S_k) in a Mott insulator. We find that while the spin-chirality terms are in general absent in the usual experimental setups of RIXS, there are prospects of realizing such terms if one considers instead the scattering near a pre-edge. We then perform detailed analyses for the square and the kagome lattices, and brief analyses for the triangular and the honeycomb lattices, in which we show that the spin-chirality terms are indeed present in all the above lattices, but that they occur at a higher order in our expansion for the kagome and the honeycomb lattices. The merit of using RIXS in addition to Raman spectroscopy to detect excitations that are coupled to the spin-chirality terms is also briefly discussed in the context of the emergent gauge boson in the U(1) Dirac spin liquid.Comment: 9 pages, 9 figures; v2: minor revisions, concurrent with the published versio