208866165
String theory and M-theory : a modern introduction
1. Introduction 2. The bosonic string 3. Conformal field theory and string interactions 4. Strings with world-sheet supersymmetry 5. Strings with space-time supersymmetry 6. T-duality and D-branes 7. The heterotic string 8. M-theory and string duality 9. String geometry 10. Flux compactifications 11. Black holes in string theory 12. Gauge theory/string theory dualities References Index.
7411732
A note on fluxes in six-dimensional string theory backgrounds
Abstract We study the structure of warped compactifications of type IIB string theory to six space–time dimensions. We find that the most general four-manifold describing the internal dimensions is conformal to a Kahler manifold, in contrast with the heterotic case where the four-manifold must be conformally Calabi–Yau.
41684471
Testing M(atrix) theory at two loops
Abstract I discuss the relation between M-theory and M(atrix)-theory in flat space by considering the effective potential for the scattering of two groups of D0-branes in both theories. An explicit calculation of this potential up to two loop order in M(atrix)-theory reveals a fascinating agreement.
2844671
Graviton scattering amplitudes in M theory
We compute graviton scattering amplitudes in M theory using Feynman rules for a scalar particle coupled to gravity in eleven dimensions. The processes that we consider describe the single graviton exchange and the double graviton exchange, that in M(atrix) theory correspond to the v^4/r^7 and v^6/r^14 term, respectively. We argue that the v^6/r^14 term appearing in M(atrix) theory at two loops can be obtained from the covariant eleven-dimensional four-graviton amplitude. Finally, we calculate the v^8/r^18 term appearing at two loops in M(atrix) theory. It has been previously conjectured that this term is related to a four graviton scattering amplitude involving the R^4 vertex of M theory.
14726887
Compactifying M-theory to four dimensions
We consider compactifications of M-theory to four-dimensional Minkowski space on seven-dimensional non-compact manifolds. These compactifications include a warp factor which is non constant due to the presence of sources coming from five-branes wrapping two-dimensional submanifolds of the internal seven-dimensional space. We derive the expression for the field strengths and consider an explicit example of this general class of solutions.
118470926
Disc amplitudes, picture changing and space-time actions
A bstractWe study in detail the procedure for obtaining couplings of D-branes to closed string fields by evaluating string theory disc amplitudes. We perform a careful construction of the relevant vertex operators and discuss the effects of inserting the boundary state which encodes the presence of the D-brane. We confront the issue of non-decoupling of BRSTexact states and prove that the problem is evaded for the computations we need, thus demonstrating that our amplitudes are automatically gauge-invariant and independent of the distribution of picture charge. Finally, we compute explicitly the two-point amplitudes of two NS-NS fields or one NS-NS and one R-R field on the disc, and we carefully compare all the lowest order terms with predictions from supergravity.
137898852
MECHANISMS AND APPLICATIONS OF NUCLEAR TRACK REGISTRATION IN POLYMERS.
40898720
A fast embedded system for radio detection of cosmic rays
For the detection of radio signals from ultra high energy (> 1017 eV) cosmic rays in the frequency range up to 80 MHz an embedded system was designed, built, and tested. A steep band-pass filter in the range of 30 to 80 MHz suppresses the main source of radio frequency interferences. To fulfill the data acquisition (DAQ) task, four 180 MHz twelve bit ADCs have to be read-out by a FPGA into a two gigabyte buffer memory. Furthermore the FPGA contains the trigger and a Altera NIOS II soft-core processor for data management. A GPS receiver controls the timing of the system. For the read-out an Ethernet-link and a CAN interface to a WLAN communication board is foreseen. The architecture of the system and the measured performance of the DAQ-board are described.
124471126
The 3rd generation Front-End cards of the Pierre Auger surface detectors: Test results and performance in the field
The surface detector array of the Pierre Auger Observatory comprises 1600 water Cherenkov detectors distributed over an area of 3000 km 2 . The Cherenkov light is detected by three 9-in. photo-multiplier tubes from which the signals of the anode and last dynode are digitized by 10 bit 40 MHz FADCs. An Altera Cyclone FPGA is employed to generate different local triggers and to handle the data transfer to a communication board. After briefly discussing the design of the cards we present an autonomous test-bench, which has been set up in order to test the large number of boards prior to installation in the field. The qualification procedure and the results obtained in the laboratory are presented. Up to three years of operation in the field demonstrate a very good performance and reliability of the Front-End cards.
120215184
A search for gamma radiation above 24 TeV energy from cosmic point sources
Abstract The HEGRA collaboration has searched for γ-ray emission from 36 potential cosmic point sources with the wide angle air Cerenkov detector AIROBICC which is part of the HEGRA cosmic ray detector complex on La Palma. AIROBICC has a γ-ray energy threshold of around 24 TeV and a mean angular resolution of 0.29 °. None of the sources could be found. Upper limits to their fluxes are given. For the VHE γ-ray emitters, the Crab nebula and Mrk 421, these flux limits are below those extrapolated from lower energy observations. Our lower limit for Mrk 421 might be interpreted either as being due to an energy cut-off in the acceleration mechanism or to the onset of γ-interaction with photons of the universal infrared background.
1694798
Design and performance of the lead-concrete geiger tower array within the HEGRA experiment
Abstract The HEGRA experiment is a hybrid installation characterized by four different types of detectors (scintillator counters, open Cherenkov counters, Cherenkov telescopes and Geiger towers) located within one detector array. The Geiger towers are built with the objective to measure the local energy deposition and to reconstruct and identify muon tracks. In addition each tower may serve as an independent high resolution muon flux monitor. With these properties the Geiger towers are operating as geometric and energetic calibration instruments for the other detector components and as additional independent measurement instruments with respect to the γ-hadron separation and the measurement of the chemical composition. In this paper the design, the performance, and the basic principles of the data analysis of the lead-concrete Geiger towers are described.