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Search Results: 1 - 10 of 22140 matches for " Space-Time "
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Leech Lattice Extension of the Non-Linear Schrodinger Equation Theory of Einstein Spaces  [PDF]
George Chapline
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.814134
Abstract: Although the scalar nonlinear Schrodinger equation has provided valuable insights into how quantum mechanics might modify the classical general relativistic description of space-time, a detailed understanding of space-times with matter has remained elusive. In this paper, we propose generalizing the nonlinear Schrodinger equation theory of Einstein spaces to include matter by transplanting the 3 + 1 dimensional theory to the 24-dimensional Leech lattice plus 1 time dimension. The scalar wave function and Chern-Simons gauge potential which encode the classical Kahler potential become 11 × 11 complex matrices belonging to a 195,442 dimensional representation of the Mathieu group M11. This theory describes gravity coupled to internal degrees of freedom which include a supersymmetric E6 × E6 Yang-Mills theory of matter.
Scale Invariant Theory of Gravitation in Einstein-Rosen Space-Time  [PDF]
Bivudutta Mishra, Pradyumn Kumar Sahoo, Addepalli Ramu
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.13027
Abstract: In this paper, we have studied the perfect fluid distribution in the scale invariant theory of gravitation, when the space-time described by Einstein-Rosen metric with a time dependent gauge function. The cosmological equations for this space-time with gauge function are solved and some physical properties of the model are studied.
Sedeonic Equations of Gravitoelectromagnetism  [PDF]
Victor L. Mironov, Sergey V. Mironov
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.510095
Abstract:

In present paper we develop the description of massless fields on the basis of space-time algebra of sixteen-component sedeons. The generalized sedeonic second-order equation for unified gravito-electromagnetic (GE) field describing simultaneously weak gravity and electromagnetism is proposed. The relations for the GE field energy, momentum and Lorentz invariants are derived. The special case of GE field described by first-order sedeonic wave equation is also discussed.

Simulation and Prediction on Space-Time Distribution of Water Quality in Dianchi Lake  [PDF]
Jun-Qiu Ren, Xian-Cheng Mao, Pin-Juan Zou
Open Journal of Modern Hydrology (OJMH) , 2013, DOI: 10.4236/ojmh.2013.31007
Abstract:

It is very important in pollution treatment to clarify the space-time distribution of water quality in Dianchi Lake. Based on the sample data obtained from 10 observation stations every month from 2008 to 2009, it uses space-time semi-variogram and ordinary kriging method to simulate the space-time variance and distribution of water quality indictors (TN, TP, BOD, CODMn, DO, Chlorophyl-α, etc.). Because the space-time semivariogram also has a certain of ex-trapolation function. From the simulation results, the pollution is mainly concentrated at the North (Caohai) and the Southwest area (Haikou), and water pollution has a increase trend.

Comparative Study of Different Space-Time Coding Schemes for MC-CDMA Systems  [PDF]
Lokesh Kumar Bansal, Aditya Trivedi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.34054
Abstract: In this paper, performance of space-time trellis-code (STTC), space-time block code (STBC), and space-time trellis-code concatenated with space-time block code (STTC-STBC) for multi-carrier code-division multiple-access (MC-CDMA) system are studied. These schemes are considered by employing different detection techniques with various multi input multi output (MIMO) antenna diversity for different number of states in multi-path fading channel. The corresponding bit error rate (BER) is obtained using simulation for minimum mean-square error (MMSE), maximum-ratio combining (MRC), and equal-gain combining (EGC) receivers employing Viterbi decoder. The simulation results show that the STTC-STBC MC-CDMA system perform better compared to other schemes considered in this paper using MMSE detection and it is also observed that the performance can also be enhanced by increasing diversity using more transmitter and receiver antennas. However, this improvement in performance comes at the cost of increased computational complexity, which is calculated for different transmitting and receiving antennas.
The Three Page Guide to the Most Important Results of M. S. El Naschie’s Research in E-Infinity Quantum Physics and Cosmology  [PDF]
M. A. Helal, L. Marek-Crnjac, Ji-Huan He
Open Journal of Microphysics (OJM) , 2013, DOI: 10.4236/ojm.2013.34020
Abstract:

In this short survey, we give a complete list of the most important results obtained by El Naschie’s E-infinity Cantorian space-time theory in the realm of quantum physics and cosmology. Special attention is paid to his recent result on dark energy and revising Einstein’s famous formula .

Analysis of Rate One Quasi-Orthogonal Space-Time Block Coding over Rayleigh Fading Channel  [PDF]
Md. Abdullah Al Amin Ranju, Ragib Shakil Rafi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2014, DOI: 10.4236/ijcns.2014.76021
Abstract:

Full-rate is very important in any data transmission coding. For transmitting data at low bit rate than full-rate code, higher modulation scheme is required. But it is impossible to design full rate orthogonal designs with complex constellation for more than two transmit antennas. Only Alamouti code provides full-rate for two transmit antennas. In this paper, Bit Error Rate (BER) is calculated for Quasi-Orthogonal Space-time Block Coding (QOSTBC). Here we work with Rayleigh fading channel. We consider the codes which decodes pairs of symbols instead of simple separate decoding like Orthogonal Space-Time Block Coding. In Quasi-Orthogonal Space-time Block Code full-rate is achieved but full-diversity is sacrificed. Diversity is the most important techniques for providing reliable communication over fading channels. One of the diversity techniques that uses multiple transmit and/or receive antennas is space diversity. Multiple antenna technique provides a space diversity to struggle with the fading without necessarily sacrificing bandwidth resources, so the excellent solutions of removing the fading of the channel for broadband wireless communications is using space diversity. Then, with the constellation rotation of the symbol, rotated version of Quasi-Orthogonal Space-Time Block Code is generated. It provides full diversity. We simulate BER for QOSTBC, rotated QOSTBC, orthogonal STBC and for uncoded system. The simulation result shows that QOSTBC and rotated QOSTBC perform better than other systems. It shows that QOSTBC provides a full transmission rate but that rotated QOSTBC provides the full rate with the full diversity.

Generalized Lagrange Structure of Deformed Minkowski Spacetime  [PDF]
Roberto Mignani, Fabio Cardone, Andrea Petrucci
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.66040
Abstract:

We discuss the generalized Lagrange structure of a deformed Minkowski space (DMS), \"\", namely a (four-dimensional) generalization of the (local) space-time based on an energy-dependent “deformation” of the usual Minkowski geometry. In \"\", local Lorentz invariance is naturally violated, due to the energy dependence of the deformed metric. Moreover, the generalized Lagrange structure of \"\" allows one to endow the deformed space-time with both curvature and torsion.


Kasner Universe in Creation-Field Cosmology  [PDF]
Kishor S. Adhav, Meena V. Dawande, Maya S. Desale, Ranjita B. Raut
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.13028
Abstract: We have studied the Hoyle-Narlikar C-field cosmology with Kasner [1,2] space-time. Using methods of Narlikar and Padmanabhan [3], the solutions have been studied when the creation field C is a function of time t only. The geometrical and physical properties of the models, thus obtained, are also studied.
Achievable Rate Regions for Orthogonally Multiplexed MIMO Broadcast Channels with Multi-Dimensional Modulation  [PDF]
Marthe KASSOUF, Harry LEIB
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.31001
Abstract: In this work, we consider a multi-antenna channel with orthogonally multiplexed non-cooperative users, and present its achievable information rate regions with and without channel knowledge at the transmitter. With an informed transmitter, we maximize the rate for each user. With an uninformed transmitter, we consider the optimal power allocation that causes the fastest convergence to zero of the fraction of channels whose mutual information is less than any given rate as the transmitter channel knowledge converges to zero. We assume a deterministic space and time dispersive multipath channel with multiple transmit and receive antennas, generating an orthogonally multiplexed Multiple-Input Multiple-Output (MIMO) broadcast system. Under limited transmit power; we consider different user specific space-time modulation formats that represent assignments of signal dimensions to transmit antennas. For the two-user orthogonally multiplexed MIMO broadcast channels, the achievable rate regions, with and without transmitter channel knowledge, evolve from a triangular region at low SNR to a rectangular region at high SNR. We also investigate the maximum sum rate for these regions and derive the associated power allocations at low and high SNR. Furthermore, we present numerical results for a two-user system that illustrate the effects of channel knowledge at the transmitter, the multi-dimensional space-time modulation format and features of the multipath channel.
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