Institut für Theoretische Physik
Start / Aktuell
April  2014
Do
24.04.2014
Sitzungssaal Mathematik
Theoretische Physik
15:15
Graduiertenkolleg 1493

Jan Schlemmer
Wien

Deformed Quantum Field Theories and Thermal
Representations



Kontakt: K.-H. Rehren
Do
24.04.2014
SR 9, C 4.101
4. Physik
16:00
Hausseminar

Tim Iffländer
IV. Physikalisches Institut

Electronic properties of the ideal Fe/GaAs(110) interface



Kontakt: Sascha Schäfer
Fr
25.04.2014
MPS
MPI für Sonnensystemforschung
10:00
MPS-Seminar

Damian Fabbian
IAC

3D MHD simulations and non-LTE spectra: modern tools for studying the Sun's composition and irradiance



Kontakt: Sami Solanki
Fr
25.04.2014
Seminarraum 11, C3.101
SFB 1073
14:15
SFB Seminar

Dr. Bernd Gotsmann
IBM Research, Zurich

Heat generation and dissipation in nanosystems

Self-heating degrades the performance of devices for logic, storage and energy conversion. Reduced thermal conductance in nano-structures has become a limiting factor towards increasing density, performance and reliability of many scaled CMOS devices. Other devices, however, may even benefit from the reduced thermal conductance, for example in thermoelectric energy converters or thermally assisted switching in various data storage schemes. The technological need for characterization of scaled nano-devices is not paralleled with the availability of methods to measure heat flux and temperature on small scales. To measure local temperature and conductance variation we therefore focus on developing measurement tools. These are based on scanning a thermometer across the sample surface region of interest, so called scanning thermal microscopy (SThM), measuring thermal properties directly through self-heating, and measuring directly the heat-flux through molecular 1D-structures. In SThM, a heater-sensor with a sharp tip is scanned across a sample surface to measure the spatial distribution of thermal conductance or temperature of a sample with a resolution down to ~10 nm. We discuss demonstrations of sensitivity and lateral resolution for both thermometry and conductance measurements using examples of graphene and organic layers and self-heated nanowires. It is shown that the surface roughness of tip and sample have critical influence on the measured thermal transport of the tip-surface contact. MEMS-based heater-sensors have been used since about a decade to measure thermal transport in nanowires, and tubes. A remaining challenge is the correlation of electrical and thermal transport properties of samples. We fabricated extremely sensitive MEMS devices to simultaneously measure thermal conductivity, electrical conductivity and thermopower. Results of a full thermoelectric characterization of single InAs nanowires are presented.

Kontakt: Prof. Konrad Samwer
Mo
28.04.2014
Seminarraum A.04.101
Theoretische Physik
14:15
Quantenfeldtheorie (Forschungsseminar M.Phy.412)

S. Preiss
Göttingen

(Semesterplanung vor dem Vortrag)

Quanten-Energie-Ungleichungen



Kontakt: K.-H. Rehren
Mo
28.04.2014
Max-Born-Hörsaal (HS2), Friedrich-Hund-Platz 1
Fakultät für Physik
16:30
Göttinger Physikalisches Kolloquium

Prof. Andrew C. Cameron (University of St Andrews,Scotland, UK )

TRANSITING EXTRA-SOLAR PLANETS: FROM HOT JUPITERS TO SUPER-EARTHS



Mo
28.04.2014
Max-Born-Hörsaal (HS2), Friedrich-Hund-Platz 1
Fakultät für Physik
16:30
Göttinger Physikalisches Kolloquium

Dr. Sandra Jeffers Universität Göttingen Institut für Astrophysik
Universität Göttingen, Institut für Astrophysik

VORSTELLUNGSVORTRAG



Di
29.04.2014
Auditorium MPS
MPI für Sonnensystemforschung
11:00
Solar-Seminar

Tim White
Uni Göttingen/MPS

Measuring Stellar Properties with Asteroseismology and Interferometry



Di
29.04.2014
Seminarraum A3.101
Theoretische Physik
14:15
Theoretisch-physikalisches Seminar

Ludwig Faddeev
Steklov I., St. Petersburg

TBA (Dilogarithms in integrable models)



Di
29.04.2014
Ludwig-Prandtl-Hörsaal, Am Faßberg 11, AI-Gebäude, 37077 Göttingen
Nichtlineare Dynamik
17:15
AG-Seminar: MPI für Dynamik und Selbstorganisation - Bernstein Focus Neurotechnology / Bernstein Center for Computational Neuroscience

Prof. em. Dr. Barry Lee
Biological Sciences, College of Optometry, State University of New York, NY

Motion and spatial signals in macaque ganglion cells

Human perception appears to rest on an achromatic, luminance channel and red-green and blue-yellow chromatic channels, which differ in their spatial and temporal characteristics. It is a matter of debate how closely these channels correspond to magno-, parvo- and koniocellular pathways of the primate visual system. I shall describe three sets of experiments: 1) localization of moving achromatic targets in a hyperacuity context: 2) localization at isoluminance: 3) segregation of signals from physiological and psychophysical channels using a novel grating stimulus, in which achromatic and chromatic components have different spatial frequencies. Taken together, the experiments strongly support strict segregation of achromatic and chromatic information in different afferent pathways.

Di
29.04.2014
SR 3, Institut für Theoretische Physik, A03.101
SFB 937
17:15
Seminar

Walter Zimmermann
University of Bayreuth

Pattern creation in nature and materials



Kontakt: C.F. Schmidt
Mi
30.04.2014
Ludwig-Prandtl-Hörsaal, Am Faßberg 11, 37077 Göttingen
MPIDS
14:15
Kolloquium

Prof. Giovanni Ciccotti
University of Rome, Italy

Time-dependent Non-equilibrium Molecular Dynamics

We present a way to extend stationary state (equilibrium and non-equilibrium) Molecular Dynamics to time dependent non-equilibrium situations, including the dynamical processes of relaxations. The procedure, which we have called Dynamical Non-Equilibrium Molecular Dynamics (D-NEMD), to distinguish it from the standard NEMD only used to simulate stationary non-equilibrium states, is based on a generalization of linear response theory, an old discovery we would like to revive. We show how this is possible in full rigor by exploiting an idea, used in the past essentially in conjunction with a subtraction technique to compute transport coefficients. The idea has been formulated by Onsager in the thirties in metaphysical language, given a solid foundation in the fifties by Green and Kubo (in the linear and nonlinear regime) and adapted to MD simulations by the present author (in collaboration with G.Jacucci and I.R.Mac Donald) in the seventies. It has been called the nonlinear Kubo-Onsager relation, connecting dynamical non-equilibrium averages or dynamical relaxations to stationary (initial distribution) averages over suitable time-evolved variables. To show the power of the method we apply it to study the relaxation of an interface between two immiscible liquids. We have shown that our method generate unbiased results while this could not be the case for the often used short time average approach. Our results to be obtained require extending the classes of non-equilibrium phenomena that can be studied by D-NEMD to the case of a complex initial ensemble consistent with a fixed macroscopic value for a scalar or a local field.

Kontakt: Marco Mazza

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