SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
It is shown through a series of calculations that neither momentum nor boosts are definable for finite energy solutions of Einstein gravity in D = 3. The contrast between the effects of Lorentz transformations on the corresponding metrics for D = 3 and D = 4 gravity is demonstrated, and some comparisons with the vector gauge treatment of the problem are offered.
The directional anisotropies of the energetic cosmic ray gas due to the relative motion between the observers frame and the one where the relativistic gas can be assumed isotropic is analyzed. The radiation fluxes formula in the former frame must follow as the Lorentz invariance of dp/E, where p, E are the 4-vector momentum-energy components; dp is the 3-volume element in the momentum space. The anisotropic flux shows in such a case an amplitude, in a rotating earth, smaller than the experimental measurements from say, EAS-arrays for primary particle energies larger than 1.E(14) eV. Further, it is shown that two consecutive Lorentz transformations among three inertial frames exhibit the violation of dp/E invariance between the first and the third systems of reference, due to the Wigner rotation. A discussion of this result in the context of the experimental anisotropic fluxes and its current interpretation is given.
Local time displacement is shown to be a true symmetry of Minkowskian physics, thereby demonstrating the empirical equivalence of different choices of the clock synchronization parameter in generalized Lorentz transformations.
Experiments with rotating systems are examined from the point of view of a test theory of the Lorentz transformations (LTs), permitting, in principle, the verification of the simultaneity relation. The significance of the experiments involved in the testing of the LTs can be determined using Robertson's test theory (RTT). A revised RTT is discussed, and attention is given to the Ehrenfest paradox in connection with the testing of the LTs.
A modern version of the Kennedy-Thorndike experiment was carried out by searching for sidereal variations between the frequency of a laser locked to an I2 reference line and a laser locked to the resonance frequency of a highly stable cavity. No variations were found at the level of 2 x 10 to the -12th. This represents a 300-fold improvement over the original Kennedy-Thorndike experiment and allows the Lorentz transformations to be deduced entirely from experiment at an accuracy level of 70 ppm.
Lorentz-Einstein transformations, coordinate transformation between accelerating systems and inertial frames of reference and clock paradox
The exact Lorentz kinematics of the Thomas precession is discussed in terms of Wigner's O(3)-like little group which describes rotations in the Lorentz frame in which the particle is at rest. A Lorentz-covariant form for the Thomas factor is derived. It is shown that this factor is a Lorentz-boosted rotation matrix, which becomes a gauge transformation in the infinite-momentum or zero-mass limit.
New tests for invariance of vacuum state under Lorentz group
Irreducible unitary representations of restricted Lorentz group on manifolds of time-, light- and spacelike 4-vectors, obtaining plane-wave solutions of Klein-Gordon equation
Propagation and radiation of waves excited by electric dipole in dispersionless uniaxial moving medium
It is known that the Lorentz group is the natural language for a given two-beam system if there are no decoherence effects. This aspect of the twobeam system formulated in terms of the six-parameter representations of the Lorentz group. It is shown that these transformations do not alter the degree of coherence. Thus, the decoherence matrices do not come from the Lorentz group. It is shown therefore that a larger group is needed to accommodate the decoherence effects in the two-beam system. This larger group is isomorphic to O(3,3) or the Lorentz group with three space and three time dimensions.
Assuming trivial action of Euclidean translations, the method of induced representations is used to derive a correspondence between massless field representations transforming under the full generalized even dimensional Lorentz group, and highest weight states of the relevant little group. This gives a connection between 'helicity' and 'chirality' in all dimensions. Restrictions on 'gauge independent' representations for physical particles that this induction imposes are also stated.
Attention has been given recently to a modified Lorentz theory (MLT) that is based on the generalized Galilean transformation. Some explicit formulas within the framework of MLT, dealing with the one-way velocity of light, slow-clock transport, and the Doppler effect are derived. A number of typical experiments are analyzed on this basis. Results indicate that the empirical equivalence between MLT and special relativity is still maintained to second order terms. The results of previous works that predict that the MLT might be distinguished from special relativity at the third order by Doppler centrifuge tests capable of a fractional frequency detection threshold of 10 to the -15th are confirmed.
It is shown that classical linear canonical transformations are possible in the Wigner phase space. Coherent and squeezed states are shown to be linear canonical transforms of the ground-state harmonic oscillator. It is therefore possible to evaluate the Wigner functions for coherent and squeezed states from that for the harmonic oscillator. Since the group of linear canonical transformations has a subgroup whose algebraic property is the same as that of the (2+1)-dimensional Lorentz group, it may be possible to test certain properties of the Lorentz group using optical devices. A possible experiment to measure the Wigner rotation angle is discussed.
It is demonstrated that an angular Fourier transformation is obtained by making a rotation around the non-compact axis of So(2,1), the Lorentz group in three dimensions.
In his letter on page 13 of the March 1993 issue, Robert Yaes raised the question of whether the existence of the cosmic microwave background (CMB), now observed so precisely with COBE, is compatible with the principle of relativity: The laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or other of two systems of coordinates in uniform translatory motion. Although I do not claim to provide an xpertresponse to this question, as desired by Yaes, it is my understanding that the principle of relativity is not necessarily violated by the mere existence of a universal reference frame. The laws of physics can still be invariant under some transformation of coordinates. This transformation is not specified by the principle of relativity itself, although we have discovered so far that Nature respects Lorentz invariance (principle of the constancy of the velocity of light).
Complex vectorial formalism in general relativity, discussing Riemann connection related to representation of Lorentz group by three- dimensional linear space
High-resolution (0.01/cm) absorption spectra of lean mixtures of CH4 in dry air were recorded with the McMath-Pierce Fourier transform spectrometer (FTS) of the National Solar Observatory on Kitt Peak at various temperatures between 24 and -61 C. The spectra have been analyzed to determine the values at room temperature of pressure-broadened widths and pressure-induced shifts of more than 740 transitions. The temperature dependence of air-broadened widths and pressure-induced shifts was deduced for approx. 370 transitions in the nu(sub 1) + nu(sub 4), nu(sub 3) + nu(sub 4), and nu(sub 2) + nu(sub 3) bands of (12)CH4 located between 4118 and 4615/cm. These results were obtained by analyzing a total of 29 spectra simultaneously using a multi-spectral non-linear least-squares fitting technique. This new technique allowed the determination of correlated spectral line parameters (e.g. intensity and broadening coefficient) better than the procedure of averaging values obtained by fitting the spectra individually. This method also provided a direct determination of the uncertainties in the retrieved parameters due to random errors. For each band analysed in this study the dependence of the various spectral line parameters upon the tetrahedral symmetry species and the rotational quantum numbers of the transitions is also presented.