12,280 research outputs found
Supersymmetry and LHC
The motivation for introduction of supersymmetry in high energy physics as
well as a possibility for supersymmetry discovery at LHC (Large Hadronic
Collider) are discussed. The main notions of the Minimal Supersymmetric
Standard Model (MSSM) are introduced. Different regions of parameter space are
analyzed and their phenomenological properties are compared. Discovery
potential of LHC for the planned luminosity is shown for different channels.
The properties of SUSY Higgs bosons are studied and perspectives of their
observation at LHC are briefly outlined.Comment: Lectures given at the 9th Moscow International School of Physics
(XXXIV ITEP Winter School of Physics
Device operation of organic tandem solar cells
A generalized methodology is developed to obtain the current-voltage characteristic of polymer tandem solar cells by knowing the electrical performance of both sub cells. We demonstrate that the electrical characteristics of polymer tandem solar cells are correctly predicted for both the series and parallel connection of the sub cells. The agreement with experiments allows us to investigate the effect of a reduced open-circuit voltage, short-circuit current or fill factor in one of the sub cells on the performance of the tandem cell. A low fill factor in one of the sub cells leads to a stronger reduction of the efficiency in a series configuration as compared to the parallel tandem device. (C) 2008 Elsevier B.V. All rights reserved
Соціально-правова та етична природа мусульманської сім‘ї
Relative sea-level variations during the late Pleistocene can only be
reconstructed with the knowledge of ice-sheet history. On the other hand, the
knowledge of regional and global relative sea-level variations is necessary
to learn about the changes in ice volume. Overcoming this problem of
circularity demands a fully coupled system where ice sheets and sea level
vary consistently in space and time and dynamically affect each other. Here
we present results for the past 410 000 years (410 kyr) from the coupling
of a set of 3-D ice-sheet-shelf models to a global sea-level model, which is
based on the solution of the gravitationally self-consistent sea-level
equation. The sea-level model incorporates the glacial isostatic adjustment
feedbacks for a Maxwell viscoelastic and rotating Earth model with coastal
migration. Ice volume is computed with four 3-D ice-sheet-shelf models for
North America, Eurasia, Greenland and Antarctica. Using an inverse approach,
ice volume and temperature are derived from a benthic δ18O stacked
record. The derived surface-air temperature anomaly is added to the
present-day climatology to simulate glacial–interglacial changes in
temperature and hence ice volume. The ice-sheet thickness variations are then
forwarded to the sea-level model to compute the bedrock deformation, the
change in sea-surface height and thus the relative sea-level change. The
latter is then forwarded to the ice-sheet models. To quantify the impact of
relative sea-level variations on ice-volume evolution, we have performed
coupled and uncoupled simulations. The largest differences of ice-sheet
thickness change occur at the edges of the ice sheets, where relative sea-level
change significantly departs from the ocean-averaged sea-level variations
Dark matter from the scalar sector of 3-3-1 models without exotic electric charges
We show that three SU(2) singlet neutral scalars (two CP-even and one CP-odd)
in the spectrum of models based on the gauge symmetry SU(3)_c X SU(3)_L X
U(1)_X, which do not contain exotic electric charges, are realistic candidates
for thermally generated self-interacting dark matter in the Universe, a type of
dark matter that has been recently proposed in order to overcome some
difficulties of collisionless cold dark matter models at the galactic scale.
These candidates arise without introducing a new mass scale in the model and/or
without the need for a discrete symmetry to stabilize them, but at the expense
of tuning several combinations of parameters of the scalar potential.Comment: RevTeX, 11 pages. v2: typos corrected, one reference added. v3:
clarifications added, four more references added. To appear in Europhys. Let
The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5
We report observations of the hot post-asymptotic giant branch star ZNG 1 in
the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic
Explorer (FUSE). From the resulting spectrum, we derive an effective
temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a
rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) =
3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon
(2.6% by mass), nitrogen (0.51%) and oxygen (0.37%) abundances. The spectrum
shows evidence for a wind with terminal velocity near 1000 km/s and an
expanding shell of carbon- and nitrogen-rich material around the star. The
abundance pattern of ZNG 1 is suggestive of the ``born-again'' scenario,
whereby a star on the white-dwarf cooling curve undergoes a very late shell
flash and returns to the AGB, but the star's rapid rotation is more easily
explained by a previous interaction with a binary companion.Comment: 8 pages, 2 PostScript figures, Latex with emulateapj5. Accepted for
publication in ApJ Letter
Trap-limited electron transport in disordered semiconducting polymers
The electron transport in diodes of poly(dialkoxy-p-phenylene vinylene) (PPV) derivatives is strongly reduced as compared to the hole transport. A recent reexamination [M. M. Mandoc , Phys. Rev. B 73, 155205 (2006)] revealed that the room-temperature electron current shows the fingerprints of trap-limited transport with a distribution of traps in energy. Here, we report on the measured temperature dependence of the electron current in these PPV derivatives. This dependence is weak and seems to be in contradiction with existing trap-limited models. We demonstrate that the presence of a Gaussian density of states (DOS) for the mobile carriers, being characteristic for disordered semiconductors, reduces the temperature dependence of the trap-limited charge transport. The reduction is governed by the width of the Gaussian DOS and originates from the equilibrium concentrations of the mobile and trapped carriers
The assessment of efforts to return to work in the European Union
Background: Assessment of efforts to promote return-to-work (RTW) includes all efforts (vocational and non-vocational) designed to improve the work ability of the sick-listed employee and increase the chance to return to work. Aim of the study was to investigate whether in 13 European countries these RTW efforts are assessed and to compare the procedures by means of six criteria. METHODS: Data were gathered in the taxonomy project of the European Union of Medicine in Assurance and Social Security and by means of an additional questionnaire. RESULTS: In seven countries RTW efforts are subject of the assessment in relation to the application for disability benefits. Description of RTW efforts is a prerequisite in five countries. Guidelines on the assessment of RTW efforts are only available in the Netherlands and no countries report the use of the ICF model. Based on the results of the additional questionnaire, the assessor is a social scientist or a physician. The information used to assess RTW efforts differs, from a report on the RTW process to medical information. A negative outcome of the assessment leads to delay of the application for disability benefits or to application for rehabilitation subsidy. Conclusion: RTW efforts are assessed in half of the participating European countries. When compared, the characteristics of the assessment of RTW efforts in the participating European countries show both similarities and differences. This study may facilitate the gathering and exchange of knowledge and experience between countries on the assessment of RTW efforts
Low-voltage polymer field-effect transistors for nonvolatile memories
We demonstrate organic nonvolatile memories based on transistors, made from spin-coated polymers, that have programming voltages of 15 V and good data retention capabilities. The low-voltage programmable ferroelectric field-effect transistors were obtained by an optimized ferroelectric polymer deposition method using cyclohexanone as a solvent from which films can be obtained that are thin, smooth and defect free. The data retention characteristics were measured for 3 h under constant read conditions. Extrapolation predicts that the data retention capability exceeds 10 years. (C) 2005 American Institute of Physics
The Kazhdan-Lusztig conjecture for finite W-algebras
We study the representation theory of finite W-algebras. After introducing
parabolic subalgebras to describe the structure of W-algebras, we define the
Verma modules and give a conjecture for the Kac determinant. This allows us to
find the completely degenerate representations of the finite W-algebras. To
extract the irreducible representations we analyse the structure of singular
and subsingular vectors, and find that for W-algebras, in general the maximal
submodule of a Verma module is not generated by singular vectors only.
Surprisingly, the role of the (sub)singular vectors can be encapsulated in
terms of a `dual' analogue of the Kazhdan-Lusztig theorem for simple Lie
algebras. These involve dual relative Kazhdan-Lusztig polynomials. We support
our conjectures with some examples, and briefly discuss applications and the
generalisation to infinite W-algebras.Comment: 11 page
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