2,335 research outputs found
Asymptotic Learning Curve and Renormalizable Condition in Statistical Learning Theory
Bayes statistics and statistical physics have the common mathematical
structure, where the log likelihood function corresponds to the random
Hamiltonian. Recently, it was discovered that the asymptotic learning curves in
Bayes estimation are subject to a universal law, even if the log likelihood
function can not be approximated by any quadratic form. However, it is left
unknown what mathematical property ensures such a universal law. In this paper,
we define a renormalizable condition of the statistical estimation problem, and
show that, under such a condition, the asymptotic learning curves are ensured
to be subject to the universal law, even if the true distribution is
unrealizable and singular for a statistical model. Also we study a
nonrenormalizable case, in which the learning curves have the different
asymptotic behaviors from the universal law
Summing Over Inequivalent Maps in the String Theory Interpretation of Two Dimensional QCD
Following some recent work by Gross, we consider the partition function for
QCD on a two dimensional torus and study its stringiness. We present strong
evidence that the free energy corresponds to a sum over branched surfaces with
small handles mapped into the target space. The sum is modded out by all
diffeomorphisms on the world-sheet. This leaves a sum over disconnected classes
of maps. We prove that the free energy gives a consistent result for all smooth
maps of the torus into the torus which cover the target space times, where
is prime, and conjecture that this is true for all coverings. Each class
can also contain integrations over the positions of branch points and small
handles which act as ``moduli'' on the surface. We show that the free energy is
consistent for any number of handles and that the first few leading terms are
consistent with contributions from maps with branch points.Comment: 17 pages, 5 eps figures contained in a uuencoded file, UVA-HET-92-1
A preliminary factor analytic investigation into the first-order factor structure of the Fifteen Factor Plus (15FQ+) on a sample of Black South African managers
The original publication is available at http://www.sajip.co.zaMoyo, S. & Theron, C. 2011. A preliminary factor analytic investigation into the first-order factor structure of the Fifteen Factor Plus (15FQ+) on a sample of Black South African managers. SA Journal of Industrial Psychology, 37(1), 1-22, doi: 10.4102/sajip.v37i1.934.Orientation: The Fifteen Factor Questionnaire Plus (15FQ+) is a prominent personality
questionnaire that organisations frequently use in personnel selection in South Africa.
Research purpose: The primary objective of this study was to undertake a factor analytic
investigation of the first-order factor structure of the 15FQ+.
Motivation for the study: The construct validity of the 15FQ+, as a measure of personality, is
necessary even though it is insufficient to justify its use in personnel selection.
Research design, approach and method: The researchers evaluated the fit of the measurement
model, which the structure and scoring key of the 15FQ+ implies, in a quantitative study that
used an ex post facto correlation design through structural equation modelling. They conducted
a secondary data analysis. They selected a sample of 241 Black South African managers from
a large 15FQ+ database.
Main findings: The researchers found good measurement model fit. The measurement model
parameter estimates were worrying. The magnitude of the estimated model parameters
suggests that the items generally do not reflect the latent personality dimensions the designers
intended them to with a great degree of precision. The items are reasonably noisy measures of
the latent variables they represent.
Practical/managerial implications: Organisations should use the 15FQ+ carefully on Black
South African managers until further local research evidence becomes available.
Contribution/value-add: The study is a catalyst to trigger the necessary additional research
we need to establish convincingly the psychometric credentials of the 15FQ+ as a valuable
assessment tool in South Africa.Publisher's versio
Observation of time quasicrystal and its transition to superfluid time crystal
We report experimental realization of a quantum time quasicrystal, and its
transformation to a quantum time crystal. We study Bose-Einstein condensation
of magnons, associated with coherent spin precession, created in a flexible
trap in superfluid He-B. Under a periodic drive with an oscillating
magnetic field, the coherent spin precession is stabilized at a frequency
smaller than that of the drive, demonstrating spontaneous breaking of discrete
time translation symmetry. The induced precession frequency is incommensurate
with the drive, and hence the obtained state is a time quasicrystal. When the
drive is turned off, the self-sustained coherent precession lives a
macroscopically-long time, now representing a time crystal with broken symmetry
with respect to continuous time translations. Additionally, the magnon
condensate manifests spin superfluidity, justifying calling the obtained state
a time supersolid or a time super-crystal
Some New/Old Approaches to QCD
This is a talk delivered at the Meeting on Integrable Quantum Field Theories,
Villa Olmo and at STRINGS 1992, Rome, September 1992. I discuss some recent
attempts to revive two old ideas regarding an analytic approach to QCD-the
development of a string representation of the theory and the large N limit of
QCD.Comment: 20 page
Heterogeneous structure of the lithosphere in the Black Sea from a multidisciplinary analysis of geophysical fields
Magnetic, gravity, geothermal, seismic and tomographic data from the lithosphere were first jointly examined. A multidisciplinary interpretation has resulted in a new and consistent model for lithospheric density, magnetic, thermal and velocity heterogeneities. Faults of different orders for the crystalline crust have been mapped in details. Large deep fault zones were recognized. Among them is the most prominent Odessa-Sinop-Ordu (OSO) fault zone, which played a key role in the opening and development of the Black Sea Depression. A fundamental difference was revealed between the crustal and mantle structure and geophysical parameters of the Western Black Sea Basin (WBSB) and Eastern Black Sea Basin (EBSB). These dissimilarities are in the size of Β«non-graniticΒ» crust, pattern and intensity of heat flow, topography of the lower boundary of the thermal lithosphere, mantle seismic velocity and structure of magnetic and residual gravity anomalies. Based on new information it was demonstrated that the WBSB and EBSB were diachronously formed on two large distinct continental blocks with independent post-rift development of the sub-basins. The rifting of the western sub-basin commenced earlier than that of the eastern one. The EBSB is characterized by younger thermal activity than the WBSB and consequently it was stabilized later. The Mid Black Sea High (MBSH) is not a single tectonic unit but is formed by two ridges of various crystalline crustal structure and age shifted relative to each other by the faults of the OSO zone
Density Correlation Functions in Calogero Sutherland Models
Using arguments from two dimensional Yang-Mills theory and the collective
coordinate formulation of the Calogero-Sutherland model, we conjecture the
dynamical density correlation function for coupling and , where is
an integer. We present overwhelming evidence that the conjecture is indeed
correct.Comment: 12 pages phyzzx, CERN-TH/94.7243 One reference change
Study successful development programming courses of the first-year students
The paper addresses the issue of training of students of IT-specialty and the impact on the success of training factors such as the results of the Unified State Exam, professional motivation and social and psychological adaptation of the first-year studentsΠ ΡΠ°Π±ΠΎΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°Π΅ΡΡΡ Π²ΠΎΠΏΡΠΎΡ ΠΎΠ± ΠΎΠ±ΡΡΠ΅Π½ΠΈΠΈ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΠ’-ΡΠΏΠ΅ΡΠΈΠ°Π»ΡΠ½ΠΎΡΡΠΈ ΠΈ Π²Π»ΠΈΡΠ½ΠΈΠΈ Π½Π° ΡΡΠΏΠ΅ΡΠ½ΠΎΡΡΡ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΡΠ°ΠΊΠΈΡ
ΡΠ°ΠΊΡΠΎΡΠΎΠ² ΠΊΠ°ΠΊ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΠ΄ΠΈΠ½ΠΎΠ³ΠΎ ΠΠΎΡΡΠ΄Π°ΡΡΡΠ²Π΅Π½Π½ΠΎΠ³ΠΎ ΠΠΊΠ·Π°ΠΌΠ΅Π½Π°, ΠΏΡΠΎΡΠ΅ΡΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠΉ ΠΌΠΎΡΠΈΠ²Π°ΡΠΈΠΈ ΠΈ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎ-ΠΏΡΠΈΡ
ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π°Π΄Π°ΠΏΡΠ°ΡΠΈΠΈ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ²-ΠΏΠ΅ΡΠ²ΠΎΠΊΡΡΡΠ½ΠΈΠΊΠΎ
Tonic GABAA conductance bidirectionally controls interneuron firing pattern and synchronization in the CA3 hippocampal network.
The spiking output of interneurons is key for rhythm generation in the brain. However, what controls interneuronal firing remains incompletely understood. Here we combine dynamic clamp experiments with neural network simulations to understand how tonic GABAA conductance regulates the firing pattern of CA3 interneurons. In baseline conditions, tonic GABAA depolarizes these cells, thus exerting an excitatory action while also reducing the excitatory postsynaptic potential (EPSP) amplitude through shunting. As a result, the emergence of weak tonic GABAA conductance transforms the interneuron firing pattern driven by individual EPSPs into a more regular spiking mode determined by the cell intrinsic properties. The increased regularity of spiking parallels stronger synchronization of the local network. With further increases in tonic GABAA conductance the shunting inhibition starts to dominate over excitatory actions and thus moderates interneuronal firing. The remaining spikes tend to follow the timing of suprathreshold EPSPs and thus become less regular again. The latter parallels a weakening in network synchronization. Thus, our observations suggest that tonic GABAA conductance can bidirectionally control brain rhythms through changes in the excitability of interneurons and in the temporal structure of their firing patterns
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