23,391 research outputs found
The Higgs Sector of the Minimal 3 3 1 Model Revisited
The mass spectrum and the eigenstates of the Higgs sector of the minimal 3 3
1 model are revisited in detail. There are discrepancies between our results
and previous results by another author.Comment: 20 pages, latex, two figures. One note and one reference are adde
Discovery of 15-second oscillations in Hubble Space Telescope observations of WZ Sagittae following the 2001 outburst
We report the discovery of 15-s oscillations in ultraviolet observations of
WZ Sge obtained with the Hubble Space Telescope approximately one month after
the peak of the 2001 outburst. This is the earliest detection of oscillations
in WZ Sge following an outburst and the first time that a signal near 15 s has
been seen to be dominant. The oscillations are quite strong (amplitude about
5%), but not particularly coherent. In one instance, the oscillation period
changed by 0.7 s between successive observations separated by less than 1 hour.
We have also found evidence for weaker signals with periods near 6.5 s in some
of our data. We discuss the implications of our results for the models that
have been proposed to account for the 28-s oscillations seen in quiescence. If
the periods of the 15-s oscillations can be identified with the periods of
revolution of material rotating about the white dwarf, the mass of the white
dwarf must satisfy M_WD > 0.71 M_sun. The corresponding limit for the 6.5-s
signals is M_WD > 1.03 M_sun.Comment: accepted for publication in ApJ Letters; 13 pages, 4 postscript
figures; new version corrects a few typos and matches version that will
appear in ApJ
Using Muonic Hydrogen in Optical Spectroscopy Experiment to Detect Extra Dimensions
Considering that gravitational force might deviate from Newton's
inverse-square law (ISL) and become much stronger in small scale, we propose a
kind of optical spectroscopy experiment to detect this possible deviation and
take electronic, muonic and tauonic hydrogen atoms as examples. This experiment
might be used to indirectly detect the deviation of ISL down to nanometer scale
and to explore the possibility of three extra dimensions in ADD's model, while
current direct gravity tests cannot break through micron scale and go beyond
two extra dimensions scenario.Comment: 9 pages, 2 figures. To appear in IJT
Tomographic measurements on superconducting qubit states
We propose an approach to reconstruct any superconducting charge qubit state
by using quantum state tomography. This procedure requires a series of
measurements on a large enough number of identically prepared copies of the
quantum system. The experimental feasibility of this procedure is explained and
the time scales for different quantum operations are estimated according to
experimentally accessible parameters. Based on the state tomography, we also
investigate the possibility of the process tomography.Comment: 12 pages, 4 figure
Recommended from our members
Gas-Phase Synthesis of Triphenylene (C18 H12 ).
For the last decades, the hydrogen-abstraction-acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C14 H9 ]. ) with vinylacetylene (C4 H4 ), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH - triphenylene (C18 H12 ) - via an unconventional hydrogen abstraction-vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level
Reactivity of the Indenyl Radical (C9 H7 ) with Acetylene (C2 H2 ) and Vinylacetylene (C4 H4 ).
The reactions of the indenyl radicals with acetylene (C2 H2 ) and vinylacetylene (C4 H4 ) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C9 H7 . ) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C6 H5 . ) and acetylene forming phenylacetylene (C6 H5 CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol-1 ) and slow, contrary to the exoergic (-38 kJ mol-1 ) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces
Modularization of multi-qubit controlled phase gate and its NMR implementation
Quantum circuit network is a set of circuits that implements a certain
computation task. Being at the center of the quantum circuit network, the
multi-qubit controlled phase shift is one of the most important quantum gates.
In this paper, we apply the method of modular structuring in classical computer
architecture to quantum computer and give a recursive realization of the
multi-qubit phase gate. This realization of the controlled phase shift gate is
convenient in realizing certain quantum algorithms. We have experimentally
implemented this modularized multi-qubit controlled phase gate in a three qubit
nuclear magnetic resonance quantum system. The network is demonstrated
experimentally using line selective pulses in nuclear magnetic resonance
technique. The procedure has the advantage of being simple and easy to
implement.Comment: to appear in Journal of Optics B: Quantum and Semiclassical Optic
Anxiety, depression, and social connectedness among the general population of eight countries during the COVID-19 pandemic
BACKGROUND: The COVID-19 pandemic affected the mental health of the general population through multiple pathways. The aim of this study was to examine anxiety, depression, self-confidence, and social connectedness among the general population of eight countries during the COVID-19 pandemic, their underlying factors, and vulnerable groups. METHODS: A web-based survey was administered to persons from the general population of China, Greece, Italy, Netherlands, Russia, Sweden, the United Kingdom, and the United States. The survey included the Generalized Anxiety Disorder-7 (GAD-7), Patient Health Questionnaire-9 (PHQ-9) and items on self-confidence, social connectedness, and socio-demographics. Data were analyzed with descriptive statistics, exploratory factor analysis and regression analysis. RESULTS: Twenty-three thousand six hundred twenty-two respondents completed the survey. Overall, 42% of the total sample had mild to severe anxiety symptoms and 43% had mild to severe depression symptoms. 14% to 38% reported suboptimal ratings in self-confidence, social participation, contact with family and friends, and feeling connected to others. In the exploratory factor analyses, in most countries, one dominant factor had a high influence on GAD-7, PHQ-9 sum scores and self-confidence with eigenvalue (% variance) above 3.2 (53.9%). One less dominant factor had a high influence on social connectedness scores with eigenvalue (% variance) ranging above 0.8 (12.8%). Being younger, female, having chronic conditions, perceived as risky to COVID-19 infection, and feeling not very well protected against COVID-19 were significantly associated with the two underlying factors. CONCLUSIONS: Anxiety, depression, and problems with self-confidence and social connectedness were highly prevalent in the general population of eight countries during the early phase of the COVID-19 pandemic. This highlights the importance of the allocation of additional resources to implement policies to mitigate the impact of the pandemic on mental health. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13690-022-00990-4
Behavior of a frustrated quantum spin chain with bond dimerization
We clarified behavior of the excitation gap in a frustrated S=1/2 quantum
spin chain with bond dimerization by using the numerical diagonalization of
finite systems and a variational approach. The model interpolates between the
independent dimer model and the S=1 spin chain by changing a strength of the
dimerization. The energy gap is minimum at the fully-frustrated point, where a
localized kink and a freely mobile anti-kink govern the low-lying excitations.
Away from the point, a kink and an antikink form a bound state by an effective
triangular potential between them. The consequential gap enhancement and the
localization length of the bound state is obtained exactly in the continuous
limit. The gap enhancement obeys a power law with exponent 2/3. The method and
the obtained results are common to other frustrated double spin-chain systems,
such as the one-dimensional J_1 - J_2 model, or the frustrated ladder model.Comment: 11 pages, REVTeX, 8 figures in eps-fil
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