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  • 1
    Electronic Resource
    Electronic Resource
    Berry's phase for photons and topology in Maxwell's theory (1990)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 31 (1990), S. 1942-1946 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The classical nature of Berry's phase for photons is shown to arise from the intrinsic topological structure of Maxwell's theory. The phase is developed in the context of fiber-bundle theory and is discussed in some detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528641
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  • 2
    Electronic Resource
    Electronic Resource
    Design and performance of singular electric field terahertz photoconducting antennas (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2076-2078 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present new designs of more efficient terahertz (THz) radiation emitters and detectors enhanced by electric field singularities using sharp and laterally offset electrodes. We compare the performances of the terahertz emission and different polarization properties resulting from these structures. An average THz radiation power of 3 μW is achieved under 20 mW excitation, calibrated by free space electro-optic sampling. We also study the gap size dependence of the THz radiation, and find an absence of a positive electrode effect in the small gap limit. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119346
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of the superconducting thin film of HgBa2Ca2Cu3O8+δ (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1723-1725 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgBa2Ca2Cu3O8+δ (Hg-1223) superconducting thin films of about 0.3 μm in thickness have been successfully synthesized. The process involves depositing films (∼ 1 μm thickness) of Ba2Ca2Cu3Ox on a SrTiO3 substrate by pulse laser ablation technique and implanting mercury ions into this deposited film, followed by annealing at oxygen atmosphere. The films so obtained show a relatively wide superconducting transition temperature up to 118 K, as determined magnetically, which is similar to that of underdoping bulk Hg-1223. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115887
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  • 4
    Electronic Resource
    Electronic Resource
    Dispersion of second-order optical properties of new high thermal stability guest chromophores (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1173-1175 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new class of high thermal stability fused-ring guest chromophores intended for incorporation into highly stable host polyimides has been successfully developed. Thermal stabilities far in excess of 300 °C have been achieved for both the pure guest and the parent guest-host systems. dc-induced second harmonic generation measurements of the microscopic second order β of the guest chromophores in solution have been performed using an optical parametric generation technique. In the near-infrared region, values of the standard product μβ of order 103×10−48 esu have been observed. These values are in good agreement with quantum many-electron calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109813
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  • 5
    Electronic Resource
    Electronic Resource
    Thermally stable poled polyquinoline thin film with very large electro-optic response (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 299-301 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Poled guest-host polyquinoline thin films are shown to demonstrate both exceptionally large electro-optic activity and long-term stability. After an initial drop from 45 to 26 pm/V in the first 100 h, the electro-optic coefficient r33 at 26 pm/V remained for more than 2000 h. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115424
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  • 6
    Electronic Resource
    Electronic Resource
    Coherent terahertz radiation detection: Direct comparison between free-space electro-optic sampling and antenna detection (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 444-446 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare the use of free-space electro-optic sampling (FSEOS) with photoconducting antennas to detect terahertz (THz) radiation in the range of 0.1–3 THz. For the same average THz power and low-frequency modulation, signal-to-noise ratio and sensitivity are better with antenna detection at frequencies smaller than 3 THz. When the modulation frequency is increased to more than 1 MHz in FSEOS, both detection schemes have comparable performance. Using a singular-electric-field THz emitter, we demonstrate the feasibility of a THz imaging system using real-time delay scanning in FSEOS and only 20 mW of laser power. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121894
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  • 7
    Electronic Resource
    Electronic Resource
    The development of a solitary wave in a channel of variable elliptical cross section (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2352-2356 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the disintegration of a solitary wave in an elliptical channel is studied when it propagates from one uniform section of the channel into another through a transition section. It is found that for an elliptical channel with constant width, fission of solitons is also possible when the solitary wave moves into a uniform section of larger depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865293
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  • 8
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    Testing gravity using cosmic voids (2015)
    Oxford University Press
    Details
    Publication Date: 2015-06-05
    Description: We explore voids in dark matter and halo fields from simulations of cold dark matter and Hu–Sawicki f ( R ) models. In f ( R ) gravity, dark matter void abundances are greater than that of general relativity (GR). Differences for halo void abundances are much smaller, but still at the 2, 6 and 14 level for the f ( R ) model parameter | f R 0 | = 10 –6 , 10 –5 and 10 –4 . Counter-intuitively, the abundance of large voids found using haloes in f ( R ) gravity is lower, which suggests that voids are not necessarily emptier of galaxies in this model. We find the halo number density profiles of voids are not distinguishable from GR, but the same voids are emptier of dark matter in f ( R ) gravity. This can be observed by weak gravitational lensing of voids, for which the combination of a spec- z and a photo- z survey over the same sky is necessary. For a volume of 1 (Gpc  h –1 ) 3 , | f R 0 | = 10 –5 and 10 –4 may be distinguished from GR at 4 and 8 using the lensing tangential shear signal around voids. Sample variance and line-of-sight projection effect sets limits for constraining | f R 0 | = 10 –6 . This might be overcome with a larger volume. The smaller halo void abundance and the stronger lensing shear signal of voids in f ( R ) models may be combined to break the degeneracy between | f R 0 | and 8 . The outflow of dark matter from void centres are 5, 15 and 35 per cent faster in f ( R ) gravity for | f R 0 | = 10 –6 , 10 –5 and 10 –4 . The velocity dispersions are greater than that in GR by similar amounts. Model differences in velocities imply potential powerful constraints for the model in phase space and in redshift space.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Voids in modified gravity: excursion set predictions (2013)
    Oxford University Press
    Details
    Publication Date: 2013-04-03
    Description: We investigate the behaviour of the fifth force in voids in chameleon models using the spherical collapse method. Contrary to Newtonian gravity, we find the fifth force is repulsive in voids. The strength of the fifth force depends on the density inside and outside the void region as well as its radius. It can be many times larger than the Newtonian force and their ratio is in principle unbound. This is very different from the case in haloes, where the fifth force is no more than 1/3 of gravity. The evolution of voids is governed by the Newtonian gravity, the effective dark energy force and the fifth force. While the first two forces are common in both cold dark matter (CDM) and chameleon universes, the fifth force is unique to the latter. Driven by the outward-pointing fifth force, individual voids in chameleon models expand faster and grow larger than in a CDM universe. The expansion velocity of the void shell can be 20–30 per cent larger for voids of a few Mpc  h –1 in radius, while their sizes can be larger by ~10 per cent. This difference is smaller for larger voids of the same density. We compare void statistics using excursion set theory; for voids of the same size, their number density is found to be larger in chameleon models. The fractional difference increases with void size due to the steepening of the void distribution function. The chance of having voids of radius ~25 Mpc  h –1 can be 2.5 times larger. This difference is about 10 times larger than that in the halo mass function. We find strong environmental dependence of void properties and population in chameleon models. The differences in size and expansion velocity with general relativity are both larger for small voids in high-density regions. In general, the difference between chameleon models and CDM in void properties (size, expansion velocity and distribution function) is larger than the corresponding quantities for haloes. This suggests that voids might be better candidates than haloes for testing gravity.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Voids in modified gravity reloaded: Eulerian void assignment (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-15
    Description: We revisit the excursion set approach to calculate void abundances in chameleon-type modified gravity theories, which was previously studied by Clampitt, Cai & Li. We focus on properly accounting for the void-in-cloud effect, i.e. the growth of those voids sitting in overdense regions may be restricted by the evolution of their surroundings. This effect may change the distribution function of voids hence affect predictions on the differences between modified gravity (MG) and general relativity (GR). We show that the thin-shell approximation usually used to calculate the fifth force is qualitatively good but quantitatively inaccurate. Therefore, it is necessary to numerically solve the fifth force in both overdense and underdense regions. We then generalize the Eulerian-void-assignment method of Paranjape, Lam & Sheth to our modified gravity model. We implement this method in our Monte Carlo simulations and compare its results with the original Lagrangian methods. We find that the abundances of small voids are significantly reduced in both MG and GR due to the restriction of environments. However, the change in void abundances for the range of void radii of interest for both models is similar. Therefore, the difference between models remains similar to the results from the Lagrangian method, especially if correlated steps of the random walks are used. As Clampitt et al., we find that the void abundance is much more sensitive to MG than halo abundances. Our method can then be a faster alternative to N -body simulations for studying the qualitative behaviour of a broad class of theories. We also discuss the limitations and other practical issues associated with its applications.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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