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Forthcoming Seminars at F-1
Tuesday
11 Dec 2018
11:15 | Lucas Hackl (MPQ Garching) | Low energy spectra from variational tangent planes |
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| Variational methods are extensively used to study properties of ground states and low excited states. By focusing on a suitable sub-manifold of states, we can overcome the exponential growth of the Hilbert space with the system size. In this talk, I will introduce a geometric framework to approximate the low lying energy spectrum by studying the linearized Hamiltonian flow on the tangent plane at the ground state. The spectrum is then given by the eigenvalues of the covariant derivative on the variational manifold. Using the paradigmatic Bose-Hubbard model as an example, I will discuss advantages compared to methods based on directly diagonalizing the Hamiltonian restricted to the tangent plane.
Seminar room for physics (JSI main building) |
Seminars Archive
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
8 Dec 2009
15:00 | Lev Vidmar | Magnetic-lattice polaron and bipolaron in the cuprates |
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V seminarski sobi odsekov za fiziko (106)
Charge carriers moving in the magnetic background are the central focus
of many microscopic models relevant to describe the properties of
cuprate superconductors. Recently, growing evidence is emerging in favor
of significance of lattice degrees of freedom in underdoped cuprates. We
explore the interplay between strong correlations and lattice degrees of
freedom in the limit of one and two doped charge carriers, which lead to
formation of a magnetic-lattice polaron and bipolaron.
I will review some results of the magnetic-lattice polaron properties,
as described by the t-J Holstein model, and introduce a more realistic
model for description of the magnetic-lattice bipolaron. I will show how
two different polarizations of quantum oxygen vibrations influence the
spacial symmetry of the bound magnetic bipolaron in the context of the
t-J model. Linear as well as quadratic electron-phonon coupling to
transverse polarization stabilize d-wave symmetry, where the existence
of a magnetic background is essential for the formation of a d-wave
bipolaron state. On the other hand, with increasing linear
electron-phonon coupling to longitudinal polarization the symmetry of a
d-wave bipolaron state changes to p wave. |
24 Nov 2009
15:00 | Ana Hocevar | Morphometry and structure of natural random tilings |
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V seminarski sobi odekov za fiziko (106).
To better understand the observed universality of their structure, we
analyze the morphometry of a set of living and inanimate planar
cellular partitions. We characterize them by the distributions of
polygon reduced area, a scale-free measure of the roundedness of
polygons. These distributions are fairly sharp and seem to belong to
the same family. By comparing the frequencies of the polygon classes,
we map all samples onto model tilings of equal-area, equal-perimeter
polygons. We argue that the random two-dimensional patterns can be
parametrized by their median reduced area alone. |
17 Nov 2009
15:00 | Prof. Vyatcheslav B. Priezzhev | Logarithmic Correlations in Lattice Models |
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V seminarski sobi odsekov za fiziko (106).
Two-point correlation functions of free-fermion models on the 2D lattice
are considered at the critical point. An origin of logarithmic corrections
to power laws is analysed. A crucial role of non-local diagrams is
revealed and illustrated by examples for the Abelian sandpile model.
Obtained results are compared with predictions of the logarithmic conformal
field theory (LCFT). |
3 Nov 2009
15:00 | Anze Losdorfer Bozic | Pok nabite, prazne virusne kapside |
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V seminarski sobi odsekov za fiziko (106).
Po kratkem
uvodu v biofiziko virusov bom predstavil preprost model poka
nabite virusne kapside, ki se nahaja v solni raztopini ob
odsotnosti virusnega genoma. Elektrostatski odboj med naboji na
posameznih proteinskih gradnikih tezi k tvorbi odprtin, docim se s pokom elektrolitu izpostavi rob kapside, kar je za
gradnike energetsko manj ugodno. Poceno kapsido aproksimiramo
kot enakomerno nabito sfericno kapico, katere elektrostatsko
prosto energijo racunamo v Poisson-Boltzmannovem priblizku
povprecnega polja, temu pa pridodamo se energijo linijske
napetosti izpostavljenega roba. Termodinamska stabilnost sistema
je tako odvisna od medsebojnega vpliva obeh prispevkov. Model
poleg tega omogoca tudi analizo razpada dveh vrst membran:
fleksibilnih membran (npr. kapsid), kjer se membrana razdeli na
dva kosa, ter tekocih membran (npr. vesiklov), kjer tvorba
odprtine poteka brez izgube materiala. |
13 Oct 2009
15:00 | Prof. Thomas Pruschke
University of Goettingen, Germany | Competing interactions and magnetic order in correlated electron systems |
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| In physics seminar room (106). |
8 Oct 2009
15:00 | Wataru Koshibae
ASI, RIKEN, Wako, Saitama, Japan | Relaxation dynamics of excited states in the spin-electron coupled systems |
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In physics seminar rook (106)
The anomalous and large cross-effect between electronic transport and
the external field is nothing more than the control of the excited
electronic states and its relaxation by the external field. In the
unconventional electron systems, highly non-trivial relaxation process
of the non-equilibrium states is expected. We have studied
numerically the relaxation process in the spin-electron coupled
systems.
We study quantum dynamics of the excited electronic states in the
double-exchange model at half-filling by solving coupled equations for
the quantum evolution of electrons and Landau-Lifshits-Gilbert
equation for classical spins. The localized spin is considered to be a
classical vector with a magnitude S. The ground state of the
double-exchange model at half filling is the antiferromagnetic
insulating state because of the perfect nesting-condition in this
system. Using finite size systems, we numerically investigate the
relaxation dynamics of excited states by calculating time evolution of
the electronic states and local spin structure.
We find that the time scale of the relaxation dynamics is fairly
longer than the inverse of the kinetic energy and interactions of
electrons, and the spatial inhomogeneity plays crucial roles. In
particular, the inter-band relaxation occurs through the in-gap state
localized near the large spin tilting from the ground state
antiferromagnetic configuration, and we find the non-adiabatic quantum
transitions through a resonant mutual precession analogous to the
electron spin resonance (ESR) process. Sensitivity of the quantum
dynamics on the parameters in the model is also investigated . |
6 Oct 2009
15:00 | Hiroaki Matsueda
Sendai National College of Technology, Japan | Time-dependent DMRG study of relaxation dynamics in photoexcited one-dimensional Mott insulator |
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In physics seminar room (106)
Strongly
correlated electron systems exhibit peculiar optical properties
that are promising for future optoelectronic devises. One of
long-standing problems is seen in one-dimensional Mott
insulators, and the problem is how to understand photoinduced
insulator-to-metal transition accompanied with its picosecond
recovery to the insulating ground state. Spin and phonon
relaxations are two possible candidates. We calculate time
dependence of the photocarrier number, the phonon number, and
the spin energy after photoexcitation in the Hubbard-Holstein
model with vector potential of pulsed laser light. Various DMRG
methods are combined for these calculations. In the absence of
the electron-phonon coupling, the spin relaxation is not
efficient even for the strong pulse that would break the
spin-charge separation. In the presence of the electron-phonon
coupling, the energy absorption of phonons are dramatically even
for small electron-phonon coupling, while the spin relaxation is
much more suppressed. In addition to the photoinduced dynamics,
I am also going to present recent development of time-dependent
DMRG and related methods. |
27 Aug 2009
12:00 | Ilja Doršner, Svjetlana Fajfer | Omejitve na leptokvarke iz fizike nizkih energij |
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| In the tea room of F-1 department. more... |
30 Jul 2009
12:00 | Gorazd Cvetič (Univ. Tecnica Federico St. Maria, Valparaiso) | Analitična QCD |
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| In the tea room of F-1 department. more... |
24 Jul 2009
11:00 | Jelena Zivkovic, Radboud University, Nijmegen | Dynamic Force Spectroscopy on RNA-Protein Complex, Data and Statistical Analysis |
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| Seminar will be at 11:15 in TEA ROOM of F1 Department |
16 Jul 2009
12:00 | Veljko Dmitrasinovic (Vinca Institute of Nuclear Sciences) | A variational estimate of the Higgs mass |
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| In the tea room of F-1 departement.
In view of the impending restart of LHC I offer a reminder of the 2.2 TeV calculation/prediction of the Higgs mass in the Standard Model based on the Gaussian functional variational approximation, by R. Ibanez-Meier,
I. Stancu and P.M. Stevenson. Z.Phys. C70, 307 (1996). I show proofs of the gauge invariance (V.D., Nuov. Cim. 109A, 1187 (1996)) and of the unitarity and causality of this calculation (I. Nakamura and V.D., Nucl. Phys. A713, 133, 2003)). more... |
9 Jul 2009
12:00 | Wei Liao (East China University of Science and Technology) | Equations and flavor transformation of neutrinos in supernova |
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| In the tea room of F-1 department.
We derive a series of moment equations describing the motion and flavor transformation of neutrinos in supernova. We find a particular series of moments of neutrino density matrix in supernova. The emission angle distribution of neutrinos is described by this series of moments. We expand the equation of neutrinos using these moments and obtain moment equations. We find that these moments have very good property of convergence and the infinite series of equations can be truncated to equations with a small set of moments. Using a small set of moment equations the required computational power is reduced by about two orders of magnitude compared to that in multi-angle simulation. The study on non-linear flavor transformation of neutrinos is substantially simplified using these equations. Two flavor system of neutrinos is also considered and new equations describing the flavor polarization vectors of neutrinos are found. more... |
30 Jun 2009
12:00 | Manimala Mitra | Type-III Seesaw with 2HDM |
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| In the tea room of F1 department.
Proof of neutrino masses and mixing from a series of outstanding experimental efforts have opened a window to physics beyond the standard model of particle physics. There must be some underlying theory which explains the very particular neutrino mass difference and mixing. It is well known that Seesaw mechanism has its success in explaining the smallness of neutrino mass. While many works have been recently done in the context of Type-III Seesaw which requires a fermionic triplet, we have concentrated on Type-III Seesaw in the presence of an additional Higgs doublet and on $\\mu-\\tau$ symmetry. In this context we have studied the phenomenological predictions and the model signatures which Type-III Seesaw with 2HDM offers. more... |
23 Jun 2009
15:00 | G. J. Rodgers
Brunel University, United Kingdom | Statistical physics and healthcare systems |
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V seminarski sobi odsekov za fiziko (106)
I present two applications of statistical physics to problems in the
provision of healthcare. In the first I present an analysis of one
years\' worth of empirical data on the arrival and discharge times at a
UK Accident and Emergency (A\\&E) department. I find that discharges rates
vary slightly with the workload, that the distribution of the length of
stay has a fat tail and that a sand pile model mimics the qualitative
behaviour of the system. In the second application the distribution of
patients\' lengths of stay in English hospitals is measured by using
routinely collected data from 11 years. It is found to be well
approximated by a power-law distribution spanning over more than 3
decades. To explain this observation, a theoretical resource allocation
model is presented. |
4 Jun 2009
12:00 | Jernej Fesel Kamenik | Signatures of Heavy Vectors in Higgsless models |
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| In the tea room of F-1 department.
One or more heavy spin-1 fields may replace the Higgs boson in keeping perturbative unitarity up to a few TeV while at the same time account for the ElectroWeak Precision Tests. We study the Drell-Yan production of heavy vector and axial-vector states of generic Higgsless models at hadron colliders. We analyse in particular the l+l-, WZ, and three SM gauge boson final states. In the l+l- case we show how present Tevatron data restricts the allowed parameter space of these models. The two and three gauge boson final states (especially WZ, WWZ, and WZZ) are particularly interesting in view of the LHC, especially for light axial-vector masses, and could shed more light on the role of spin-1 resonances in the electroweak precision tests. more... |
28 May 2009
12:45 | Jonathan Rocher (ULB Brussels) | Challenges for hybrid inflation: SUSY GUTs, spectral index and initial conditions |
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Now that CMB observational data increased in precision, the question of
which (class of) models are the best candidates to realize inflation is
particularly urging. Hybrid inflation is one of the three main classes
of inflationary models and is considered very motivated among high
energy physicists. After a quick review about hybrid inflation and the
reasons why it is popular in the high energy community, I will discuss
the phenomenology of these models and the challenges they have to face.
I will first review some consequences of embedding it in SUSY GUTs :
the difficulty to find an inflaton candidate and the constraints
imposed by the formation of cosmic strings. I will then turn to two of
its main problems: the blue spectral index in disagreement with WMAP5
and the space of initial conditions for inflation to be successful. I
will show that the slow roll approximation should not always be trusted
to study the model, and discuss what we learn from the exact dynamics
in terms of spectral index and ways to realize hybrid inflation. We
have used numerical resolution of the dynamics to understand and study
the properties of the initial condition space available for successful
inflation. I will show that both problems mentioned above can be
avoided by considering superplanckian initial values for the fields and
discuss the consequences for the models.
Based on arXiv:0809.4355, hep-ph/0406120, hep-ph/0308134
as well as work in progress : A. Mazumdar, J. Rocher, \ more... |
21 May 2009
13:00 | Bojan Golli | Uganke Roperjeve resonance |
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| In the IJS seminar room (n. 106). more... |
20 May 2009
13:00 | prof. dr. Sergei Kruchinin
BITP, Kiev, Ukraine | Thermoelectricity in double-barrier structure with resonant tunneling |
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| V seminarski sobi odsekov za fiziko (106) |
19 May 2009
15:00 | dr. Jernej Mravlje | Vpliv fononv na Kondov pojav v nanoskopskih sistemih |
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V seminarski sobi odsekov za fiziko (106)
Kvantne pike in molekularni mosticki predstavljajo nanoskopske
realizacije Andersonovega modela magnetnih
necistoc. Prevodnost teh sistemov pri nizkih temperaturah je
namrec ojacana zaradi Kondovega pojava. V molekularnih
mostickih je poleg Coulombskega odboja pomembna tudi sklopitev na
fonone dveh tipov: na molekularna lastna nihanja in na oscilacije
molekul med kontakti. Medtem ko vpliv prvih lahko opisemo z
renormalizacijo parametrov modela, drugi sklapljajo molekulo na
dodatni prevodni kanal, kar lahko vodi do kvalitativno drugacnega
obnasanja. V seminarju bom predstavil analiticne in
numericne rezultate v modelih za fonone obeh tipov.
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14 May 2009
12:00 | Eung Jin Chun (KIAS, Seul, Korea) | LFV and leptogenesis in Higgs exampt no-scale supergravity |
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| In the IJS seminar room (n. 106) more... |
12 May 2009
15:00 | dr. Jorgen Rammer
Inst. of Phys., Umea University, Sweden | Counting statistics of interfering Bose-Einstein condensates |
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| In Physics seminar room (106). |
7 May 2009
15:00 | prof. dr. Roberto Serra
Modena and Reggio Emilia University | Synchronization in protocell models |
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In physics seminar room (106)
Protocells are lipid vesicles (or, less frequently) micelles which are
endowed with some rudimentary metabolism and contain {\\it genetic}
material, and which should be able to grow, reproduce and
evolve. While viable protocells do not yet exist, their study is
important in order to understand possible scenarios for the origin of
life, as well as for creating new {\\it protolife} forms which are able to
adapt and evolve. This endeavour has an obvious theoretical interest,
but it might also lead to an entirely new {\\it living technology},
definitely different from conventional biotechnology.
Theoretical models can be extremely useful to devise possible
protocell architectures and to forecast their behaviour. In this talk
I will address an important issue in protocell research. What can be
called the {\\it genetic material} of a protocell is composed by a set
of molecules which, collectively, are able to replicate themselves. At
the same time, the whole protocell undergoes a growth process (its
metabolism) followed by a breakup into two daughter cells. This
breakup is a physical phenomenon which is frequently observed in lipid
vesicles, and it has nothing to do with life, although it
superficially resembles the division of a cell. In order for evolution
to be possible, some genetic molecules should affect the rate of
duplication of the whole container, and some mechanisms have been
proposed whereby this can be achieved.
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23 Apr 2009
12:00 | Matej Pavsic | O posplositvi prostora-casa: teorija relativnosti v konfiguracijskem prostoru |
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| In the tea room of F-1 departmet. more... |
17 Apr 2009
11:00 | Jure Zupan | General Minimal Flavor Mediation |
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| In the tea room of F-1 department. more... |
31 Mar 2009
15:00 | Jun-ichi Fukuda, (AIST, Japonska) | Theory and simulation of liquid crystal anchoring on a grooved surface |
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Location: Physics seminar room (106)
Surface anchoring is a tendency of liquid crystal molecules
to align along some specific direction with respect to
a confining surface. The understanding of the origin and
mechanism of surface anchoring is an important subject of
liquid crystal science.
In 1972, Berreman proposed a theory of surface anchoring
induced by a microscopically grooved surface[1].
His theory is based on an idea that liquid crystal molecules
tend to align along the groove direction to minimize the
elastic energy of the liquid crystal distortions.
The deviation of the average orientation of liquid crystals
from the groove direction costs energy, which is the origin
of the surface anchoriqng energy.
His theory, although simple enough,
has been regarded as capturing the essence of surface anchoring
and widely accepted in the field.
However, his theory was criticized very recently[2], and
it was revealed that his theory is based on an invalid assumption
in the treatment of the liquid crystal distortions
and cannot incorporate properly the contribution of so-called
surfacelike elasticity.
In this talk, I will show how Berreman\'s theory
should be modified and give the correct formula
for the anchoring energy as a function of the average orientation
of liquid crystals with respect to the groove direction.
I will also argue that our theory is readily
extended to surfaces with arbitrary groove patterns[3].
Furthermore, I will present some numerical attempts[4]
to evaluate the anchoring energy and compare our numerical
results with theory.
References:
[1] D.W. Berreman, Phys. Rev. Lett. 28, 1683 (1972); Mol. Cryst. Liq. Cryst. 23, 215 (1973).
[2] J. Fukuda, M. Yoneya and H. Yokoyama, Phys. Rev. Lett. 98, 187803 (2007); ibid. 99, 139902(Erratum) (2007).
[3] J. Fukuda, J.S. Gwag, M. Yoneya and H. Yokoyama, Phys. Rev. E 77, 011702 (2008).
[4] J. Fukuda, M. Yoneya and H. Yokoyama, Phys. Rev. E 77, 030701(R) (2008); ibid. 79, 011705 (2009) |
12 Mar 2009
12:00 | Ho-Ung Yee (ICTP) | Holographic Monopole Catalysis of Baryon Decay |
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| In the tea room of F-1 department. more... |
10 Mar 2009
15:00 | prof. Jan Forsman,
Chemical Center, Univer. of Lund, Sweden | Density functional theories of Coulomb fluids |
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In physics seminar room (106)
Most current density functional theories relies upon the presence of
hard cores, also between ions of like charge. These hard cores
should in principle reflect exchange repulsion. However, by the way in which these
theories are formulated, the hard cores
effectively determine the range of ion-ion correlations. In this talk, I will present
alternative density functional theories to describe aqueous salt solutions.
In these approaches, an approximation of the relevant {\\it Coulomb hole} that results from
correlations between like-charged ions, is calculated (rather than chosen ad hoc)
for the system under study. |
5 Mar 2009
14:00 | Michiyasu Mori,
Institute for Materials Research, Sendai | Electronic states of iron-based superconductors |
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Physics seminar room (106).
We will give a brief review on the iron-based superconductors, and
remark some puzzles on superconductivity and antiferromagnetism in
this compound. Electronic states will be discussed from viewpoint of
material dependence. In this study, the band structure composed of Fe
and As is calculated by the Slater and Koster\'s method to give hopping
integrals of Fe-Fe and Fe-As bonds. It is found that the spectral
weight near the Fermi energy is dominated by yz, zx and x2-y2
orbitals. Depending on materials, the most dominant orbital changes
among these orbitals. In terms of crystal field, the yz and zx
orbitals are higher in energy around the regular tetragonal of As, and
superconducting critical temperature is maximum. On the other hand, yz
and zx orbitals become lower in energy for a distorted tetragonal, in
which the antiferromagnetic state occurs accompanied by structural
change. Hence, such an orbital crossover must be crucial for the
electronic states as superconductivity and antiferromagnetism. We will
show some preliminary results by the Hartree-Fock calculation of
multi-band Hubbard model.
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26 Feb 2009
12:00 | Jure Drobnak | Kratek pregled fizike top kvarka in predstavitev nase analize razpada t --> c l+l- |
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| In the tea room of F1 department. more... |
29 Jan 2009
12:00 | Ivica Picek (Univ. of Zagreb) | New TeV-scale Quark in Rare K and B Decays |
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| In the tea room of F1 department.
It is conceivable that possible new quark states can be out of the direct LHC production reach, and that one could infer on them from their virtual loop effects. We introduce a secondary top state allowed by the existing electroweak precision tests. This state satisfies the requirements of small CKM unitarity violation and minimal flavour violation, and we examine its effects on selected rare K and B decays. It turns out that such rather heavy extra top has the best chance to be recovered via an increase in B_s -> mu^+ mu^- decay rate measured at the LHC. more... |
22 Jan 2009
12:00 | Lorenzo Calibbi (SISSA, Trieste) | Gauge coupling unification with magic fields |
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| In the tea room of F1 department.
We consider field sets that do not form complete SU(5) multiplets, but exactly preserve the one-loop MSSM prediction for alpha_3(M_Z) independently of the value of their mass. The unification scale is in general affected by such new fields and can be raised to larger values. These ``magic\'\' fields represent a useful tool in GUT model building: they can be used to fix gauge coupling unification in two-step breakings of the unified group, to suppress large KK thresholds in models with extra dimensions, or they can be interpreted as messengers of supersymmetry breaking in GMSB models. more... |
20 Jan 2009
15:00 | O. S. Barišić | Single static impurity in a Heisenberg chain |
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In physics seminar room (106).
The effect of a single static impurity on the many-body states and on the spin and thermal transport in the one dimensional anisotropic Heisenberg chain at finite temperatures is studied. Whereas due to integrability the pure Heisenberg model exhibits Poisson level statistics and dissipationless transport within the chain, it is found using the numerical approach that at least at high enough temperature a single impurity induces Wigner-Dyson level statistics and incoherent transport with a well defined current relaxation rate. |
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7 Dec, 2018 Seminar:
Dec 11: Low energy spec...
Lucas Hackl (MPQ Garchi... | 30 Nov, 2018 Seminar:
Dec 4: DC-transport pr...
Jan Skolimowski (JSI)... | 28 Nov, 2018 Publication:
Vidmar L., Hackl L., Bi...
Phys. Rev. Lett. 121... | 2 Nov, 2018 Seminar:
Nov 6: Cesium solitons...
Tadej Mežnaršič (F-5... | 26 Oct, 2018 Publication:
Zhang Y., Vidmar L. and...
Phys. Rev. A 98... | 24 Oct, 2018 Abroad:
Invited Talk
Nejc Košnik... | 24 Oct, 2018 Abroad:
Invited Talk
Jernej F. Kamenik... | 19 Oct, 2018 Seminar:
Oct 23: The smothered p...
Friedrich Krien... |
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