سبحان خواجه وند (دانشکده فیزیک دانشگاه صنعتی شریف)
چکیده:همانگونه که زمان میتواند به تنهایی برای فلاسفه موضوع قابل بحثی باشد برای فیزیکدان نیز اینگونه است. از زمان ارائه نسبیت تا کنون دگرگونی بزرگ در درک ما از زمان حاصل نشده است. در تحولات بنیادین فیزیک همواره زمان به نوعی اهمیت داشته یکی از جنبه های بررسی زمان خود را در ترمودینامیک و مکانیک آماری نشان میدهد، چرا که ارتباطاتی بین مفهوم انتروپی و جهت زمان میتوان متصور بود. تجربه زمان را در یک جهت نشان میدهد، اما معادلات فیزیکی زیادی هستند که نسبت به زمان متقارن هستند. انتروپی برای سیستمها همواره در حال افزایش است و اگر این افزایش انتروپی نماینده جهت زمان باشد ممکن است بتوان به الزاماتی برای این همسویی رسید که درک عمیقتری از زمان حاصل گردد. مدلهایی برای درک این ارتباط ارائه شده اند از جمله این مدلها مدل صریح حلقه ای کک میباشد. این مدل نمونه بسیار خوبی برای درک جهت زمان میباشد. این نمونه به خوبی بدون اینکه نیاز به ریاضیات چندان پیچیده ای باشد نشان میدهد که وابستگی عمیقی بین درک ما از زمان و احتمالات وجود دارد. در این سمینار سعی شده تاریخچه مختصری از درک از زمان و مدل کک که به آن اشاره شد داده شود.
In the upcoming Spring semester, Dr. Raphael Raynaud from IPM, will present a course on Magneto-Hydrodynamic for B.Sc and Master students in Physics Department of Sharif University.
The course pre-registration will be done via department office and Ms. Yaghoubi.
The time-schedule of class can be fixed later by the mutual agreement of instructor and students.
Details:
Dynamo theory
Raphaël Raynaud
1. Description
Magnetic fields are observed in various astrophysical objects like galaxies, stars and planets that, quoting Keith Moffatt (1978), “it is probably safe to state that a magnetic field is a normal accompaniment of any cosmic body that is both fluid (wholly or in part) and rotating”. It is currently believed that most cosmic magnetic fields that we observe have been, and still are, continuously created by an electromagnetic inductive process known as the dynamo effect. This course is intended to be an introduction to the dynamo theory with a particular focus on direct numerical simulations, leading up to present-day research questions. 2. Prerequisites
Students are assumed to have basic knowledge in vector analysis, linear algebra, elementary theory of differential equations, complex variables and elements of fluid mechanics and electrodynamics (Maxwell’s equations). Programming notions with the Python language may be useful. Note that the course will be in English. 3. Organization
This is intended to be a lecture course, but short oral presentations (in English) are envisaged. Depending of the computing facilities, hands-on sessions with the 3D MHD spherical shell code MagIC can be organized. If not, data set can be provided to learn basic post-processing tasks.
Abstract: The word “quantization” is used both in physics and mathematics in many different senses. The common basis of all these theories is that the classical and quantum mechanics are just different realizations of the same abstract scheme. Geometric quantization goal is the construction of quantum objects using the geometry of the corresponding classical objects as a point of departure. The geometric quantization procedure falls into the following three steps: prequantization, polarization and metaplectic correction. Prequantization produces a natural Hilbert space together with a quantization procedure for observables that exactly transforms Poisson brackets on the classical side into commutators on the quantum side. Nevertheless, the prequantum Hilbert space is generally understood to be “too big”. The idea is that one should then select a Poisson commuting set of n-variables on the 2n-dimensional phase space and consider functions that depend only on these n variables. The n variables can be either real-valued, resulting in a position-style Hilbert space, or complex valued. A polarization is a coordinate independent description on such a choice of n Poisson-commuting functions. The metaplectic correction is a technical modification of the above procedure that is necessary in the case of real polarization and often convenient for complex polarization.
Large Scale Structure: Our last chance to discover the hidden scenario of Early Universe
محمد انصاری (دانشکده فیزیک دانشگاه صنعتی شریف)
Abstract: The inflationary models solve several problems of cosmology, such as horizon problem and the flatness of the Universe. But however there are lots of inflationary models which Cosmic Microwave Background (CMB) can’t rule out them now. Non-Gaussianity and tensor perturbation are two complementary probes for inflationary models. This is because the inflationary models have different predictions for these two observables, however they are not detected yet. The deviation of the scale invariance of the primordial power spectrum is another opportunity which is detected by CMB data but with low statistical significance. In this presentation I will talk about the last opportunity and justify how Large Scale Structure will help us to rule out more inflationary models or the inflation scenario itself (through some idea about clock signal models which is developed recently).
Korea Astronomy and Space Science Institute, South Korea
Abstract: Strong gravitational lensing systems contain a wealth of information that can be used to estimate the expansion history of the universe. The light rays from different images of a source quasar experience different gravitational potentials and optical paths which result a time delay in the associated light curves. A reliable estimation of the time delay has crucial role in the process of expansion history estimation. In this talk we describe our proposed algorithm for time delay estimation which shows outstanding results in the Time Delay Challenge (TDC). This algorithm consists of the smoothing and cross-correlation methodologies as well as a quick way for error estimation. In continue we explain the modified version of this algorithm which recently we have developed. In this version we introduce a new time delay estimator which includes weighted cross-correlation and some other changes in the procedure of estimation. The modified algorithm shows more precise results on TDC simulated data. At the end we discuss the estimation of time delay related to the light curves of the lensed quasar SDSS J1001+5027 system and compare our results with the time delays obtained by different group of researchers for the same system.
We will have a Stellar Light Curve Analysis Workshop next week. Tuesday – Wednesday and Thursday 7- 8 – 9 day (27-28-29 December) from 8:00 to 16:00in Physics Department of Sharif University of Technology.
Instructors: Dr. Sedighe Sadjadian (SUT) and Dr. Farhang Habibi (LAL-IN2P3/CNRS).
In order to participate to this workshop you have to attend the preliminary session which will be held Sunday 5 day – 25 December @ 15:00 in Partovi Hall – Physics Department of SUT.
In order to participate to the workshop you have to send your email address to Miss Liaghi with email address: fatemehliaghi95-AT-gmail.com.
Preliminary knowledge of Astronomy and Computer skills (Linux , Python or/and C++ ) is desirable.
The workshop has no registration fee and accordingly the lunch and breaks are not supported.
