Two-Flavor Lattice QCD with a Finite Density of Heavy Quarks: Heavy-Dense Limit and "Particle-Hole" Symmetry

We investigate the properties of the half-filling point in lattice QCD (LQCD), in particular the disappearance of the sign problem and the emergence of an apparent particle-hole symmetry, and try to understand where these properties come from by studying the heavy-dense fermion determinant and the corresponding strong-coupling partition function (which can be integrated analytically). We then add in a first step an effective Polyakov loop gauge action (which reproduces the leading terms in the character expansion of the Wilson gauge action) to the heavy-dense partition function and try to analyze how some of the properties of the half-filling point change when leaving the strong coupling limit. In a second step, we take also the leading nearest-neighbor fermion hopping terms into account (including gauge interactions in the fundamental representation) and mention how the method could be improved further to incorporate the full set of nearest-neighbor fermion hoppings. Using our mean-field method, we also obtain an approximate ($\mu$,T) phase diagram for heavy-dense LQCD at finite inverse gauge coupling $\beta$. Finally, we propose a simple criterion to identify the chemical potential beyond which lattice artifacts become dominant.Comment: 39 pages, 22 figure

Euclidean Dynamical Triangulation revisited: is the phase transition really first order?

The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [3,4]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [3,4] an artificial harmonic potential was added to the action; in [4] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated. In the present work, we address the above weaknesses: we allow the volume to fluctuate freely within a fixed interval; we take measurements after a fixed number of attempted moves; and we overcome critical slowing down by using an optimized parallel tempering algorithm [6]. With these improved methods, on systems of size up to 64k 4-simplices, we confirm that the phase transition is first order.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

Euclidean Dynamical Triangulation revisited: is the phase transition really 1st order? (extended version)

The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [5,9]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [5,9] an artificial harmonic potential was added to the action; in [9] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated. In the present work, we address the above weaknesses: we allow the volume to fluctuate freely within a fixed interval; we take measurements after a fixed number of attempted moves; and we overcome critical slowing down by using an optimized parallel tempering algorithm [12]. With these improved methods, on systems of size up to 64k 4-simplices, we confirm that the phase transition is first order. In addition, we discuss a local criterion to decide whether parts of a triangulation are in the elongated or crumpled state and describe a new correspondence between EDT and the balls in boxes model. The latter gives rise to a modified partition function with an additional, third coupling. Finally, we propose and motivate a class of modified path-integral measures that might remove the metastability of the Markov chain and turn the phase transition into second order.Comment: 26 pages, 21 figures, extended version of arXiv:1311.471

#Leadershipaccelerated: A Coach Mindset Focused Leadership Development Program

Problem: Developing leaders to lead in environments that are dynamic, complex, and ambiguous is an area of focus for healthcare leaders. How leaders lead and how organizations develop leaders is tied to the outcomes they achieve (Development Dimensions International [DDI], 2019; Moldoveanu & Narayandas, 2019; Till, Dutta, & McKimm, 2016). To create a climate of trust and safety where teams succeed requires leaders to embed key attributes and competencies into their day-to-day work. Context: A leader’s ability to create a climate of trust and safety and to adopt and apply a coach mindset to their work is intended to help them lead self, lead others, and lead the business while positively impacting confidence, trust/psychological safety, and employee engagement (Center for Creative Leadership, 2019, Rindlisbacher, 2020). Interventions: The #Leadershipaccelerated program was developed and implemented in a way to reinforce and embed a coach mindset into the day-to-day behaviors of leaders. The program was composed of a series of 2-hour learning modules, a 360 assessment, and one-on-one coaching. The program was implemented using virtual classroom technology in an integrated healthcare delivery setting. Measures: The overall goal of the project was to help leaders increase their confidence and adopt a coach mindset in a way that improves the climate, as measured by trust/psychological safety, and employee engagement. Pre- and post-implementation measurements of confidence, psychological safety, and engagement, along with session evaluations, were collected. Results: Frontline leaders from laboratory services, nursing, and other corporate shared service areas participated in the program. Significant improvements (p ≤ .05) in confidence and psychological safety were achieved. Engagement results, pre- and post-implementation, are not yet available. The COVID-19 pandemic was a confounding variable which affected participation rates and influenced the outcomes achieved and applicability of the results to a broader audience. Conclusions: Combining one-on-one coaching with other leadership development activities was successful, reinforced the adoption and application of a coach mindset, and began to create a climate that improves trust/psychological safety. The ability to sustain the gains and ultimately change the culture of an organization will require ongoing efforts. Additional application and research in the use of a coach mindset as a leadership behavior would be beneficial, particularly considering the small sample size and confounding factor of the COVID-19 pandemic

Sampling of General Correlators in Worm Algorithm-based Simulations

Using the complex $\phi^4$-model as a prototype for a system which is simulated by a worm algorithm, we show that not only the charged correlator $$, but also more general correlators such as$$ or $$, as well as condensates like$$, can be measured at every step of the Monte Carlo evolution of the worm instead of on closed-worm configurations only. The method generalizes straightforwardly to other systems simulated by worms, such as spin or sigma models.Comment: 43 pages, 15 figure

Oscillating propagators in heavy-dense QCD

Using Monte Carlo simulations and extended mean field theory calculations we show that the $3$-dimensional $Z_3$ spin model with complex external fields has non-monotonic spatial correlators in some regions of its parameter space. This model serves as a proxy for heavy-dense QCD in $(3+1)$ dimensions. Non-monotonic spatial correlators are intrinsically related to a complex mass spectrum and a liquid-like (or crystalline) behavior. A liquid phase could have implications for heavy-ion experiments, where it could leave detectable signals in the spatial correlations of baryons.Comment: 16 pages, 9 figures, updated to match published versio

Zur Verteidigung des »Protestant Cause«: Die konfessionelle Diplomatie Englands und der eidgenössischen Orte Zürich und Bern 1655/56

The diplomatic relations between the English Republic under Oliver Cromwell and the two Swiss Cantons Zurich and Berne were heavily influenced by the bond of religion, which transnationally connected actors, events and strategies on both sides throughout the investigation period 1655/56. During the residence of the English envoy John Pell in Switzerland two major events occurred – the persecution of the Vaudois in Piedmont and the first Villmergen War – which brought together different actors for the so-called defense of Protestantism. Prominently involved beside the English diplomats and the Swiss magistrates were several leading ministers of the Reformed churches in Zurich and Berne. For both conflicts, very similar strategies were used (days of repentance and prayer, monetary aid, diplomatic and military intervention), which demonstrated a Protestant solidarity across borders and a union in the community of the faith. These measures were intended to overcome confessional differences on the inside and to close ranks against the (Catholic) enemies on the outside. Furthermore, comparable rhetoric strategies were used by both the English and the Swiss to stress a threat to the Protestant body and to generate prompt assistance to the endangered coreligionists. Inthe end, the close diplomatic relations turned out to be disappointing for both sides andremained a temporary episode; Cromwell as well as the Reformed Swiss Cantons increasinglyleaned towards an alliance with France, which made the English-Swiss convergencemore and more obsolete

Spin models in complex magnetic fields : A hard sign problem

Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these points. In this study, we couple the N-state Potts model in different ways to a complex external magnetic field and discuss the above mentioned phenomena and their relations based on analytic calculations (1D) and results obtained using a modified cluster algorithm (general D) that in many cases either cures or at least drastically reduces the sign-problem induced by the complex external field. © The Authors, published by EDP Sciences, 2018.Peer reviewe

Bulk-preventing actions for SU(N) gauge theories

We introduce a one-parameter family of SU(N) gauge actions which, when used in combination with an HMC update algorithm, prevent the gauge system from entering an artificial bulk-"phase". We briefly discuss the mechanism behind the bulk-prevention and present test results for different SU(N) gauge groups.Peer reviewe