Multidimensional replica-exchange method for free-energy calculations

We have developed a new simulation algorithm for free-energy calculations. The method is a multidimensional extension of the replica-exchange method. While pairs of replicas with different temperatures are exchanged during the simulation in the original replica-exchange method, pairs of replicas with different temperatures and/or different parameters of the potential energy are exchanged in the new algorithm. This greatly enhances the sampling of the conformational space and allows accurate calculations of free energy in a wide temperature range from a single simulation run, using the weighted histogram analysis method.Comment: 13 pages, (ReVTeX), 9 figures. J. Chem. Phys. 113 (2000), in pres

PENGARUH MATA KULIAH PERENCANAAN PENGAJARAN FISIKA TERHADAP MATA KULIAH PENGAJARAN MIKRO PADA MAHASISWA FISIKA SEMESTER GENAP 2016/2017 FKIP UNSYIAH

Permasalahan dalam penelitian ini yaitu Bagaimanakah pengaruh mata kuliah perencanaan pngajaran fisika terhadap pengajaran mikro pada mahasiswa fisika semester genap 2016/2017 Fkip Unsyiah?. Dimana penelitian ini bertujuan untuk mengetahui pengaruh mata kuliah perencanaan pengajaram fisika terhadap pengajaran mikro pada mahasiswa fisika semester genap 2016/2017 FKIP Unsyiah. Populasi dalam penelitian ini adalah mahasiwa fisika FKIP Unsyiah semester genap 2016/2017 yang sedang melaksanakan praktik pengajaran mikro dan telah lulus dalam mata kuliah perencanaan pengajaran fiska. Teknik pengumpulan data menggunakan Studi Dokumentasi dan Observasi. Teknik analisis data menggunakan analisis statistik dengan rumus analisis regresi. Hasil penelitian diperoleh thitung > ttabel (2.56 > 1.7). Hal ini berarti ada pengaruh antara mata kuliah perencanaan fisika terhadap pengajaran mikro pada mahasiswa fisika FKIP Unsyiah tahun 2017. Disarankan untuk mahasiswa praktikan pengjaran mikro terlebih dahulu mendalami materi pada mata kuliah perencanaan pengjaran fisika.Kata Kunci : Pengaruh, perencanaan pengajaran fisika, pengajaran mikro

Detection of Macroscopic Entanglement by Correlation of Local Observables

We propose a correlation of local observables on many sites in macroscopic quantum systems. By measuring the correlation one can detect, if any, superposition of macroscopically distinct states, which we call macroscopic entanglement, in arbitrary quantum states that are (effectively) homogeneous. Using this property, we also propose an index of macroscopic entanglement.Comment: Although the index q was proposed for mixed states, it is also applicable to pure states, on which we fix minor bugs (that will be reported in PRL as erratum). The conclusions of the paper remain unchanged. (4 pages, no figures.

Role of an intermediate state in homogeneous nucleation

We explore the role of an intermediate state (phase) in homogeneous nucleation phenomenon by examining the decay process through a doubly-humped potential barrier. As a generic model we use the fourth- and sixth-order Landau potentials and analyze the Fokker-Planck equation for the one-dimensional thermal diffusion in the system characterized by a triple-well potential. In the low temperature case we apply the WKB method to the decay process and obtain the decay rate which is accurate for a wide range of depth and curvature of the middle well. In the case of a deep middle well, it reduces to a doubly-humped-barrier counterpart of the Kramers escape rate: the barrier height and the curvature of an initial well in the Kramers rate are replaced by the arithmetic mean of higher(or outer) and lower(or inner) partial barriers and the geometric mean of curvatures of the initial and intermediate wells, respectively. It seems to be a universal formula. In the case of a shallow-enough middle well, Kramers escape rate is alternatively evaluated within the standard framework of the mean-first-passage time problem, which certainly supports the WKB result. The criteria whether or not the existence of an intermediate state can enhance the decay rate are revealed.Comment: 9pages, 11figure

Correlations of observables in chaotic states of macroscopic quantum systems

We study correlations of observables in energy eigenstates of chaotic systems of a large size $N$. We show that the bipartite entanglement of two subsystems is quite strong, whereas macroscopic entanglement of the total system is absent. It is also found that correlations, either quantum or classical, among less than $N/2$ points are quite small. These results imply that chaotic states are stable. Invariance of these properties under local operations is also shown.Comment: 5 pages, 2 figure

Using Pilot Systems to Execute Many Task Workloads on Supercomputers

High performance computing systems have historically been designed to support applications comprised of mostly monolithic, single-job workloads. Pilot systems decouple workload specification, resource selection, and task execution via job placeholders and late-binding. Pilot systems help to satisfy the resource requirements of workloads comprised of multiple tasks. RADICAL-Pilot (RP) is a modular and extensible Python-based pilot system. In this paper we describe RP's design, architecture and implementation, and characterize its performance. RP is capable of spawning more than 100 tasks/second and supports the steady-state execution of up to 16K concurrent tasks. RP can be used stand-alone, as well as integrated with other application-level tools as a runtime system