Complete Photoionization Experiments via Ultrafast Coherent Control with Polarization Multiplexing II: Numerics & Analysis Methodologies

The feasibility of complete photoionization experiments, in which the full set of photoionization matrix elements are determined, using multiphoton ionization schemes with polarization-shaped pulses has recently been demonstrated [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)]. Here we extend on our previous work to discuss further details of the numerics and analysis methodology utilised, and compare the results directly to new tomographic photoelectron measurements, which provide a more sensitive test of the validity of the results. In so doing we discuss in detail the physics of the photoionziation process, and suggest various avenues and prospects for this coherent multiplexing methodology

Maximum information photoelectron metrology

Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are a high-information, coherent observable. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, 3D, photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyse the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral features, but also indicate unexpected symmetry-breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum information measurements of this coherent observable

Distinct magnetotransport and orbital fingerprints of chiral bobbers

While chiral magnetic skyrmions have been attracting significant attention in the past years, recently, a new type of a chiral particle emerging in thin films $-$ a chiral bobber $-$ has been theoretically predicted and experimentally observed. Here, based on theoretical arguments, we provide a clear pathway to utilizing chiral bobbers for the purposes of future spintronics by uncovering that these novel chiral states possess inherent transport fingerprints that allow for their unambiguous electrical detection in systems comprising several types of chiral states. We reveal that unique transport and orbital characteristics of bobbers root in the non-trivial magnetization distribution in the vicinity of the Bloch points, and demonstrate that tuning the details of the Bloch point topology can be used to drastically alter the emergent response properties of chiral bobbers to external fields, which bears great potential for engineering chiral dynamics and cognitive computing.Comment: Supplementary available upon reques

Auction fever: the unrecognized effects of incidental arousal

Despite countless anecdotes about emotionally-charged bidding in auctions, there is little research to help understand what causes auction fever and why it persists. Because research has only considered how integral arousal (i.e., arousal from within the auction) affects bidding, the current research considered whether incidental arousal (i.e., arousal from outside the auction) also increases bidding. With two different manipulations of arousal, Experiments 1 and 2 showed that incidental arousal increased bidding in live auctions with monetary stakes. Experiment 1 also measured arousal physiologically to demonstrate its role in bidding. Experiment 3 utilized a third manipulation of incidental arousal and found that individuals were unaware of its effects. Overall, the current research demonstrates how bidders are potentially subject to many different sources of arousal that have nothing to do with auctions, all of which can unwittingly increase individuals’ bidding

A model for correlations in stock markets

We propose a group model for correlations in stock markets. In the group model the markets are composed of several groups, within which the stock price fluctuations are correlated. The spectral properties of empirical correlation matrices reported in [Phys. Rev. Lett. {\bf 83}, 1467 (1999); Phys. Rev. Lett. {\bf 83}, 1471 (1999.)] are well understood from the model. It provides the connection between the spectral properties of the empirical correlation matrix and the structure of correlations in stock markets.Comment: two pages including one EPS file for a figur

Agents Play Mix-game

In mix-game which is an extension of minority game, there are two groups of agents; group1 plays the majority game, but the group2 plays the minority game. This paper studies the change of the average winnings of agents and volatilities vs. the change of mixture of agents in mix-game model. It finds that the correlations between the average winnings of agents and the mean of local volatilities are different with different combinations of agent memory length when the proportion of agents in group 1 increases. This study result suggests that memory length of agents in group1 be smaller than that of agent in group2 when mix-game model is used to simulate the financial markets.Comment: 8 pages, 6 figures, 3 table

Revealing puddles of electrons and holes in compensated topological insulators

Three-dimensional topological insulators harbour metallic surface states with exotic properties. In transport or optics, these properties are typically masked by defect-induced bulk carriers. Compensation of donors and acceptors reduces the carrier density, but the bulk resistivity remains disappointingly small. We show that measurements of the optical conductivity in BiSbTeSe$_2$ pinpoint the presence of electron-hole puddles in the bulk at low temperatures, which is essential for understanding DC bulk transport. The puddles arise from large fluctuations of the Coulomb potential of donors and acceptors, even in the case of full compensation. Surprisingly, the number of carriers appearing within puddles drops rapidly with increasing temperature and almost vanishes around 40 K. Monte Carlo simulations show that a highly non-linear screening effect arising from thermally activated carriers destroys the puddles at a temperature scale set by the Coulomb interaction between neighbouring dopants, explaining the experimental observation semi-quantitatively. This mechanism remains valid if donors and acceptors do not compensate perfectly.Comment: 11 pages with 7 figures plus supplemental material (3 pages

40Ar/39Ar hornblende ages from southwestern Maine: evidence for Late Paleozoic metamorphism

40Ar/39Ar analyses of hornblendes from a 120 km long NE-trending transect within die high-grade rocks of the Casco Bay Group provide information regarding the timing of thermal events and subsequent cooling history of this region. In die north, plateau ages of 368-372 Ma record the time of cooling through argon closure temperatures (500°C) following Acadian metamorphism. In die central portion of the transect, hornblendes display younger ages (350-323 Ma) and release spectra which show evidence of a Late Paleozoic thermal overprint. To the soudi, significantly lower plateau ages are recorded (270-290 Ma). These lower ages date either die time of a Late Paleozoic diermal event or the time of cooling following a prolonged period of burial at deep crustal levels. The former interpretation is favored on the basis of the disturbed release spectra in the central portion of the transect and the fact that ages over the 60 km long southern portion of die transect are relatively constant at 280 ±10 Ma. If a Late Paleozoic thermal event occurred in this region it was evidently not accompanied by large amounts of deformation as structural evidence for such an event is lacking. The exact nature of the Late Paleozoic resetting of hornblendes in this portion of the Casco Bay Group is not clear; however, it may be related to die events which lead to granite emplacement 275 Ma ago in die Massabesic Gneiss Complex and the 272-282 Ma ages for monazites from die nearby Sebago Batholith. RÉSUMÉ Des analyses 40Ar/39Ar, effectuées sur des hornblendes prélevées sur une traverse NE de 120 km de longueur au sein des roches métamorphiques de haut degré du Groupe de Casco Bay, ont foumi des données sur l'âge des épisodes thermiques et l'histoire du refroidissement qui leur succéda dans ce secteur. Au nord, des âges-plateaux de 368 à 372 Ma datent le refroidissement via les tempeéatures de fermeture de 1'argon (500°C) sui vant le métamorphisme acadien. Dans la portion centrale de la traverse, les hornblendes exhibent des âges plus jeunes (350 a 325 Ma) et des spectres de diffusion qui portent la trace d'une surimprcssion thermique tardi-paléozoique. Vers le sud, on enregistre des âges-plateaux bien plus jeunes (270 â 290 Ma). Ces demiers datent soil un épisode thermique tardi-paléozoique, soil un refroidissement après un enfouissement prolongé profondément dans la croûte. On favorise la première interprètation à cause des spectres de diffusion dérangés que montre la portion centrale. de la traverse el parce que les âges obtenus au long des 60 km de la portion sud de la traverse sont rélativement constants à 280 +10Ma. Si cette région à subi un épisode thermique tardi-paléozoique, ce ne fut assurement pas de pair avec une déformation importante puisque la structure ne foumil aucun indice d'un tel événcment. La nature exacte de la remise à zéo tardi-paléozoiquedes hornblendes dans cette portion du Groupe de Casco Bay n'est pas apparente. On pourrait ce pendant la relier aux événements à l'origine de l'emplacement de granite dans le Complexe de Gneiss de Massabesic (il y a 275 Ma) ainsi qu'aux âges de 272-282 Ma des monazites du batholitc avoisinant de Sebago. [Traduit par le journal

Scaling of the distribution of fluctuations of financial market indices

We study the distribution of fluctuations over a time scale $\Delta t$ (i.e., the returns) of the S&P 500 index by analyzing three distinct databases. Database (i) contains approximately 1 million records sampled at 1 min intervals for the 13-year period 1984-1996, database (ii) contains 8686 daily records for the 35-year period 1962-1996, and database (iii) contains 852 monthly records for the 71-year period 1926-1996. We compute the probability distributions of returns over a time scale $\Delta t$, where $\Delta t$ varies approximately over a factor of 10^4 - from 1 min up to more than 1 month. We find that the distributions for $\Delta t \leq$ 4 days (1560 mins) are consistent with a power-law asymptotic behavior, characterized by an exponent $\alpha \approx 3$, well outside the stable L\'evy regime $0 < \alpha < 2$. To test the robustness of the S&P result, we perform a parallel analysis on two other financial market indices. Database (iv) contains 3560 daily records of the NIKKEI index for the 14-year period 1984-97, and database (v) contains 4649 daily records of the Hang-Seng index for the 18-year period 1980-97. We find estimates of $\alpha$ consistent with those describing the distribution of S&P 500 daily-returns. One possible reason for the scaling of these distributions is the long persistence of the autocorrelation function of the volatility. For time scales longer than $(\Delta t)_{\times} \approx 4$ days, our results are consistent with slow convergence to Gaussian behavior.Comment: 12 pages in multicol LaTeX format with 27 postscript figures (Submitted to PRE May 20, 1999). See http://polymer.bu.edu/~amaral/Professional.html for more of our work on this are

Eroding market stability by proliferation of financial instruments

We contrast Arbitrage Pricing Theory (APT), the theoretical basis for the development of financial instruments, with a dynamical picture of an interacting market, in a simple setting. The proliferation of financial instruments apparently provides more means for risk diversification, making the market more efficient and complete. In the simple market of interacting traders discussed here, the proliferation of financial instruments erodes systemic stability and it drives the market to a critical state characterized by large susceptibility, strong fluctuations and enhanced correlations among risks. This suggests that the hypothesis of APT may not be compatible with a stable market dynamics. In this perspective, market stability acquires the properties of a common good, which suggests that appropriate measures should be introduced in derivative markets, to preserve stability.Comment: 26 pages, 8 figure