The s-wave SU(5) monopole-fermion system reduces to a coupled set of exactly solvable QFTs
NASA Astrophysics Data System (ADS)
Craigie, N. S.; Nahm, W.
1984-11-01
By establishing that the SU(2) colour sector of fermions in the SU(5) 't Hooft-Polyakov monopole system has an underlying SU(2) Kac-Moody algebra with central charge unity, we show for massless fermions that the whole system can be reduced to a coupled set of exactly integrable two-dimensional QFT's in radial space. Consequently all the non-perturbative effects in the Green functions governing baryon number non-conservation can be explicitly computed up to the effect of the ordinary QCD confining vacuum, which is relevant only at long distances from the monopole's core.
Miller, M C; Reus, J F; Matzke, R P; Arrighi, W J; Schoof, L A; Hitt, R T; Espen, P K; Butler, D M
2001-02-07
This paper describes the Sets and Fields (SAF) scientific data modeling system. It is a revolutionary approach to interoperation of high performance, scientific computing applications based upon rigorous, math-oriented data modeling principles. Previous technologies have required all applications to use the same data structures and/or meshes to represent scientific data or lead to an ever expanding set of incrementally different data structures and/or meshes. SAF addresses this problem by providing a small set of mathematical building blocks--sets, relations and fields--out of which a wide variety of scientific data can be characterized. Applications literally model their data by assembling these building blocks. A short historical perspective, a conceptual model and an overview of SAF along with preliminary results from its use in a few ASCI codes are discussed.
Entrepreneurial Academics: Developing Scientific Careers in Changing University Settings
ERIC Educational Resources Information Center
Duberley, Joanne; Cohen, Laurie; Leeson, Elspeth
2007-01-01
This paper examines the impact of entrepreneurial initiatives within universities on scientific careers. Based on the career accounts of university-based bioscientists involved in a government-sponsored entrepreneurship training initiative, the paper explores the concept of academic entrepreneurialism. Three groups were identified in the data.…
Entanglement in fermionic systems
Banuls, Mari-Carmen; Cirac, J. Ignacio; Wolf, Michael M.
2007-08-15
The anticommuting properties of fermionic operators, together with the presence of parity conservation, affect the concept of entanglement in a composite fermionic system. Hence different points of view can give rise to different reasonable definitions of separable and entangled states. Here we analyze these possibilities and the relationship between the different classes of separable states. The behavior of the various classes when taking multiple copies of a state is also studied, showing that some of the differences vanish in the asymptotic regime. In particular, in the case of only two fermionic modes all the classes become equivalent in this limit. We illustrate the differences and relations by providing a complete characterization of all the sets defined for systems of two fermionic modes. The results are applied to Gibbs states of infinite chains of fermions whose interaction corresponds to a XY Hamiltonian with transverse magnetic field.
Fermions from classical statistics
Wetterich, C.
2010-12-15
We describe fermions in terms of a classical statistical ensemble. The states {tau} of this ensemble are characterized by a sequence of values one or zero or a corresponding set of two-level observables. Every classical probability distribution can be associated to a quantum state for fermions. If the time evolution of the classical probabilities p{sub {tau}} amounts to a rotation of the wave function q{sub {tau}}(t)={+-}{radical}(p{sub {tau}}(t)), we infer the unitary time evolution of a quantum system of fermions according to a Schroedinger equation. We establish how such classical statistical ensembles can be mapped to Grassmann functional integrals. Quantum field theories for fermions arise for a suitable time evolution of classical probabilities for generalized Ising models.
NASA Technical Reports Server (NTRS)
Strecker, Kevin; Truscott, Andrew; Partridge, Guthrie; Chen, Ying-Cheng
2003-01-01
Dual evaporation gives 50 million fermions at T = 0.1 T(sub F). Demonstrated suppression of interactions by coherent superposition - applicable to atomic clocks. Looking for evidence of Cooper pairing and superfluidity.
SAF - Sets and Fields parallel I/O and scientific data modeling system
Energy Science and Technology Software Center (ESTSC)
2005-07-01
SAF is being developed as part of the Data Models and Formats (DMF) component of the Accelerated Strategic Computing Initiative (ASCI). SAF represents a revolutionary approach to interoperation of high performance, scientific computing applications based upon rigorous, math oriented data modeling principles. Previous technologies have required all applications to use the same data structures and/or mesh objects to represent scientific data or lead to an ever expanding set of incrementally different data structures and/or meshmore » objects. SAF addresses this problem by providing a small set of mathematical building blocks, sets, relations and fields, out of which a wide variety of scientific data can be characterized. Applications literally model their data by assembling these building blocks. Sets and fields building blocks are at once, both primitive and abstract: * They are primitive enough to model a wide variety of scientific data. * They are abstract enough to model the data in terms of what it represents in a mathematical or physical sense independent of how it is represented in an implementation sense. For example, while there are many ways to represent the airflow over the wing of a supersonic aircraft in a computer program, there is only one mathematical/physical interpretation: a field of 3D velocity vectors over a 2D surface. This latter description is immutable. It is independent of any particular representation or implementation choices. Understanding this what versus how relationship, that is what is represented versus how it is represented, is key to developing a solution for large scale integration of scientific software.« less
SAF - Sets and Fields parallel I/O and scientific data modeling system
Matzke, Robb; Illescas, Eric; Espen, Peter; Jones, Jake S.; Sjaardema, Gregory; Miller, Mark C.; Schoof, Larry A.; Reus, James F.; Arrighi, William; Hitt, Ray T.; O'Brien, Matthew J.
2005-07-01
SAF is being developed as part of the Data Models and Formats (DMF) component of the Accelerated Strategic Computing Initiative (ASCI). SAF represents a revolutionary approach to interoperation of high performance, scientific computing applications based upon rigorous, math oriented data modeling principles. Previous technologies have required all applications to use the same data structures and/or mesh objects to represent scientific data or lead to an ever expanding set of incrementally different data structures and/or mesh objects. SAF addresses this problem by providing a small set of mathematical building blocks, sets, relations and fields, out of which a wide variety of scientific data can be characterized. Applications literally model their data by assembling these building blocks. Sets and fields building blocks are at once, both primitive and abstract: * They are primitive enough to model a wide variety of scientific data. * They are abstract enough to model the data in terms of what it represents in a mathematical or physical sense independent of how it is represented in an implementation sense. For example, while there are many ways to represent the airflow over the wing of a supersonic aircraft in a computer program, there is only one mathematical/physical interpretation: a field of 3D velocity vectors over a 2D surface. This latter description is immutable. It is independent of any particular representation or implementation choices. Understanding this what versus how relationship, that is what is represented versus how it is represented, is key to developing a solution for large scale integration of scientific software.
NASA Astrophysics Data System (ADS)
Javarone, Marco Alberto
2016-08-01
We study the structure of fermionic networks, i.e. a model of networks based on the behavior of fermionic gases, and we analyze dynamical processes over them. In this model, particle dynamics have been mapped to the domain of networks, hence a parameter representing the temperature controls the evolution of the system. In doing so, it is possible to generate adaptive networks, i.e. networks whose structure varies over time. As shown in previous works, networks generated by quantum statistics can undergo critical phenomena as phase transitions and, moreover, they can be considered as thermodynamic systems. In this study, we analyze fermionic networks and opinion dynamics processes over them, framing this network model as a computational model useful to represent complex and adaptive systems. Results highlight that a strong relation holds between the gas temperature and the structure of the achieved networks. Notably, both the degree distribution and the assortativity vary as the temperature varies, hence we can state that fermionic networks behave as adaptive networks. On the other hand, it is worth to highlight that we did not finding relation between outcomes of opinion dynamics processes and the gas temperature. Therefore, although the latter plays a fundamental role in gas dynamics, on the network domain, its importance is related only to structural properties of fermionic networks.
NASA Astrophysics Data System (ADS)
Stokes, George Gabriel; Larmor, Joseph
2010-06-01
Volume 1: Preface; Part I. Personal and Biographical; Part II. General Scientific Career; Part IIIa. Special Scientific Correspondence; Appendix; Index. Volume 2: Part. III. Special Scientific Correspondence; Index.
NASA Astrophysics Data System (ADS)
Wang, Zhijun; Alexandradinata, A.; Cava, Robert J.; Bernevig, B. Andrei
Spatial symmetries in crystals are distinguished by whether they preserve the spatial origin. We show how this basic geometric property gives rise to a new topology in band insulators. We study spatial symmetries that translate the origin by a fraction of the lattice period, and find that these nonsymmorphic symmetries protect a novel surface fermion whose dispersion is shaped like an hourglass; surface bands connect one hourglass to the next in an unbreakable zigzag pattern. These exotic fermions are materialized in the large-gap insulators: KHg X (X = As,Sb,Bi), which we propose as the first material class whose topology relies on nonsymmorphic symmetries. Beside the hourglass fermion, a different surface of KHg X manifests a 3D generalization of the quantum spin Hall effect. To describe the bulk topology of nonsymmorphic crystals, we propose a non-Abelian generalization of the geometric theory of polarization. Our nontrivial topology originates not from an inversion of the parity quantum numbers, but rather of the rotational quantum numbers, which we propose as a fruitful in the search for topological materials. Finally, KHg X uniquely exemplifies a cohomological insulator, a concept that we will introduce in a companion work.
Wang, Zhijun; Alexandradinata, A; Cava, R J; Bernevig, B Andrei
2016-04-14
Spatial symmetries in crystals may be distinguished by whether they preserve the spatial origin. Here we study spatial symmetries that translate the origin by a fraction of the lattice period, and find that these non-symmorphic symmetries protect an exotic surface fermion whose dispersion relation is shaped like an hourglass; surface bands connect one hourglass to the next in an unbreakable zigzag pattern. These 'hourglass' fermions are formed in the large-gap insulators, KHgX (X = As, Sb, Bi), which we propose as the first material class whose band topology relies on non-symmorphic symmetries. Besides the hourglass fermion, another surface of KHgX manifests a three-dimensional generalization of the quantum spin Hall effect, which has previously been observed only in two-dimensional crystals. To describe the bulk topology of non-symmorphic crystals, we propose a non-Abelian generalization of the geometric theory of polarization. Our non-trivial topology originates from an inversion of the rotational quantum numbers, which we propose as a criterion in the search for topological materials. PMID:27075096
Mead, Geoffrey; Lammerding, Anna M; Cox, Nelson; Doyle, Michael P; Humbert, Florence; Kulikovskiy, Alexander; Panin, Alexander; do Nascimento, Vladimir Pinheiro; Wierup, Martin
2010-08-01
Concerns about foodborne salmonellosis have led many countries to introduce microbiological criteria for certain food products. If such criteria are not well-grounded in science, they could be an unjustified obstacle to trade. Raw poultry products are an important part of the global food market. Import and export ambiguities and regulatory confusion resulting from different Salmonella requirements were the impetus for convening an international group of scientific experts from 16 countries to discuss the scientific and technical issues that affect the setting of a microbiological criterion for Salmonella contamination of raw chicken. A particular concern for the group was the use of criteria implying a zero tolerance for Salmonella and suggesting complete absence of the pathogen. The notion can be interpreted differently by various stakeholders and was considered inappropriate because there is neither an effective means of eliminating Salmonella from raw poultry nor any practical method for verifying its absence. Therefore, it may be more useful at present to set food safety metrics that involve reductions in hazard levels. Such terms as "zero tolerance" or "absence of a microbe" in relation to raw poultry should be avoided unless defined and explained by international agreement. Risk assessment provides a more meaningful approach than a zero tolerance philosophy, and new metrics, such as performance objectives that are linked to human health outcomes, should be utilized throughout the food chain to help define risk and identify ways to reduce adverse effects on public health. PMID:20819373
The Gaussian entropy of fermionic systems
Prokopec, Tomislav; Schmidt, Michael G.; Weenink, Jan
2012-12-15
We consider the entropy and decoherence in fermionic quantum systems. By making a Gaussian Ansatz for the density operator of a collection of fermions we study statistical 2-point correlators and express the entropy of a system fermion in terms of these correlators. In a simple case when a set of N thermalised environmental fermionic oscillators interacts bi-linearly with the system fermion we can study its time dependent entropy, which also represents a quantitative measure for decoherence and classicalization. We then consider a relativistic fermionic quantum field theory and take a mass mixing term as a simple model for the Yukawa interaction. It turns out that even in this Gaussian approximation, the fermionic system decoheres quite effectively, such that in a large coupling and high temperature regime the system field approaches the temperature of the environmental fields. - Highlights: Black-Right-Pointing-Pointer We construct the Gaussian density operator for relativistic fermionic systems. Black-Right-Pointing-Pointer The Gaussian entropy of relativistic fermionic systems is described in terms of 2-point correlators. Black-Right-Pointing-Pointer We explicitly show the growth of entropy for fermionic fields mixing with a thermal fermionic environment.
EUDAT and EPOS moving towards the efficient management of scientific data sets
NASA Astrophysics Data System (ADS)
Fiameni, Giuseppe; Bailo, Daniele; Cacciari, Claudio
2016-04-01
This abstract presents the collaboration between the European Collaborative Data Infrastructure (EUDAT) and the pan-European infrastructure for solid Earth science (EPOS) which draws on the management of scientific data sets through a reciprocal support agreement. EUDAT is a Consortium of European Data Centers and Scientific Communities whose focus is the development and realisation of the Collaborative Data Infrastructure (CDI), a common model for managing data spanning all European research data centres and data repositories and providing an interoperable layer of common data services. The EUDAT Service Suite is a set of a) implementations of the CDI model and b) standards, developed and offered by members of the EUDAT Consortium. These EUDAT Services include a baseline of CDI-compliant interface and API services - a "CDI Gateway" - plus a number of web-based GUIs and command-line client tools. On the other hand,the EPOS initiative aims at creating a pan-European infrastructure for the solid Earth science to support a safe and sustainable society. In accordance with this scientific vision, the mission of EPOS is to integrate the diverse and advanced European Research Infrastructures for solid Earth Science relying on new e-science opportunities to monitor and unravel the dynamic and complex Earth System. EPOS will enable innovative multidisciplinary research for a better understanding of the Earth's physical and chemical processes that control earthquakes, volcanic eruptions, ground instability and tsunami as well as the processes driving tectonics and Earth's surface dynamics. Through the integration of data, models and facilities EPOS will allow the Earth Science community to make a step change in developing new concepts and tools for key answers to scientific and socio-economic questions concerning geo-hazards and geo-resources as well as Earth sciences applications to the environment and to human welfare. To achieve this integration challenge and the
Cooling an acute muscle injury: can basic scientific theory translate into the clinical setting?
Bleakley, C M; Glasgow, P; Webb, M J
2012-03-01
Ice is commonly used after acute muscle strains but there are no clinical studies of its effectiveness. By comparison, there are a number of basic scientific studies on animals which show that applying ice after muscle injury has a consistent effect on a number of important cellular and physiological events relating to recovery. Some of these effects may be temperature dependant; most animal studies induce significant reductions in muscle temperature at the injury site. The aim of this short report was to consider the cooling magnitudes likely in human models of muscle injury and to discuss its relevance to the clinical setting. Current best evidence shows that muscle temperature reductions in humans are moderate in comparison to most animal models, limiting direct translation to the clinical setting. Further important clinical questions arise when we consider the heterogenous nature of muscle injury in terms of injury type, depth and insulating adipose thickness. Contrary to current practice, it is unlikely that a 'panacea' cooling dose or duration exists in the clinical setting. Clinicians should consider that in extreme circumstances of muscle strain (eg, deep injury with high levels of adipose thickness around the injury site), the clinical effectiveness of cooling may be significantly reduced. PMID:21677317
The Scientific Basis of Uncertainty Factors Used in Setting Occupational Exposure Limits
Dankovic, D. A.; Naumann, B. D.; Maier, A.; Dourson, M. L.; Levy, L. S.
2015-01-01
The uncertainty factor concept is integrated into health risk assessments for all aspects of public health practice, including by most organizations that derive occupational exposure limits. The use of uncertainty factors is predicated on the assumption that a sufficient reduction in exposure from those at the boundary for the onset of adverse effects will yield a safe exposure level for at least the great majority of the exposed population, including vulnerable subgroups. There are differences in the application of the uncertainty factor approach among groups that conduct occupational assessments; however, there are common areas of uncertainty which are considered by all or nearly all occupational exposure limit-setting organizations. Five key uncertainties that are often examined include interspecies variability in response when extrapolating from animal studies to humans, response variability in humans, uncertainty in estimating a no-effect level from a dose where effects were observed, extrapolation from shorter duration studies to a full life-time exposure, and other insufficiencies in the overall health effects database indicating that the most sensitive adverse effect may not have been evaluated. In addition, a modifying factor is used by some organizations to account for other remaining uncertainties—typically related to exposure scenarios or accounting for the interplay among the five areas noted above. Consideration of uncertainties in occupational exposure limit derivation is a systematic process whereby the factors applied are not arbitrary, although they are mathematically imprecise. As the scientific basis for uncertainty factor application has improved, default uncertainty factors are now used only in the absence of chemical-specific data, and the trend is to replace them with chemical-specific adjustment factors whenever possible. The increased application of scientific data in the development of uncertainty factors for individual chemicals also
The Scientific Basis of Uncertainty Factors Used in Setting Occupational Exposure Limits.
Dankovic, D A; Naumann, B D; Maier, A; Dourson, M L; Levy, L S
2015-01-01
The uncertainty factor concept is integrated into health risk assessments for all aspects of public health practice, including by most organizations that derive occupational exposure limits. The use of uncertainty factors is predicated on the assumption that a sufficient reduction in exposure from those at the boundary for the onset of adverse effects will yield a safe exposure level for at least the great majority of the exposed population, including vulnerable subgroups. There are differences in the application of the uncertainty factor approach among groups that conduct occupational assessments; however, there are common areas of uncertainty which are considered by all or nearly all occupational exposure limit-setting organizations. Five key uncertainties that are often examined include interspecies variability in response when extrapolating from animal studies to humans, response variability in humans, uncertainty in estimating a no-effect level from a dose where effects were observed, extrapolation from shorter duration studies to a full life-time exposure, and other insufficiencies in the overall health effects database indicating that the most sensitive adverse effect may not have been evaluated. In addition, a modifying factor is used by some organizations to account for other remaining uncertainties-typically related to exposure scenarios or accounting for the interplay among the five areas noted above. Consideration of uncertainties in occupational exposure limit derivation is a systematic process whereby the factors applied are not arbitrary, although they are mathematically imprecise. As the scientific basis for uncertainty factor application has improved, default uncertainty factors are now used only in the absence of chemical-specific data, and the trend is to replace them with chemical-specific adjustment factors whenever possible. The increased application of scientific data in the development of uncertainty factors for individual chemicals also has
Stereoscopy in Static Scientific Imagery in an Informal Education Setting: Does It Matter?
NASA Astrophysics Data System (ADS)
Price, C. Aaron; Lee, H.-S.; Malatesta, K.
2014-12-01
Stereoscopic technology (3D) is rapidly becoming ubiquitous across research, entertainment and informal educational settings. Children of today may grow up never knowing a time when movies, television and video games were not available stereoscopically. Despite this rapid expansion, the field's understanding of the impact of stereoscopic visualizations on learning is rather limited. Much of the excitement of stereoscopic technology could be due to a novelty effect, which will wear off over time. This study controlled for the novelty factor using a variety of techniques. On the floor of an urban science center, 261 children were shown 12 photographs and visualizations of highly spatial scientific objects and scenes. The images were randomly shown in either traditional (2D) format or in stereoscopic format. The children were asked two questions of each image—one about a spatial property of the image and one about a real-world application of that property. At the end of the test, the child was asked to draw from memory the last image they saw. Results showed no overall significant difference in response to the questions associated with 2D or 3D images. However, children who saw the final slide only in 3D drew more complex representations of the slide than those who did not. Results are discussed through the lenses of cognitive load theory and the effect of novelty on engagement.
NASA Astrophysics Data System (ADS)
Cook, H. M.; Cook, G. W.
2015-12-01
The mystery box is a well-known and well-loved teaching tool designed to encourage students to engage in making observations in order to draw conclusions. We have adapted this exercise, normally used in laboratory settings, for use in a lecture setting in introductory earth science classes. We have tied it to the scientific method such that students are engaging in mystery-box- based inquiry while exploring the steps of the scientific method. It is used in conjunction with a PowerPoint presentation that illustrates and discusses the steps and process integral to the scientific method, which is fundamental to science. Students are encouraged to explore the formal and informal use of the scientific method throughout their educational careers and in their daily lives. Furthermore, students are challenged to analyze the necessity of the scientific method as means for conducting scientific inquiry and exploring the results of such inquiry. A follow-up assignment to the activity asks students to evaluate the efficacy of the activity and associated PowerPoint and discussion. Students consistently report having enjoyed and learned from the process.
ERIC Educational Resources Information Center
Fives, Allyn; Russell, Daniel W.; Canavan, John; Lyons, Rena; Eaton, Patricia; Devaney, Carmel; Kearns, Norean; O'Brien, Aoife
2015-01-01
In a randomized controlled trial (RCT), treatments are assigned randomly and treatments are withheld from participants. Is it ethically permissible to conduct an RCT in a social setting? This paper addresses two conditions for justifying RCTs: that there should be a state of equipoise and that the trial should be scientifically promising.…
ERIC Educational Resources Information Center
Furberg, Anniken; Ludvigsen, Sten
2008-01-01
This article reports on a study concerning secondary school students' meaning-making of socio-scientific issues in Information and Communication Technology-mediated settings. Our theoretical argument has as its point of departure the analytical distinction between "doing science" and "doing school," as two different forms of classroom activity. In…
Fermionization and Hubbard models
NASA Astrophysics Data System (ADS)
Dargis, P.; Maassarani, Z.
1998-12-01
We introduce a transformation which allows the fermionization of operators of any one-dimensional spin-chain. This fermionization procedure is independent of any eventual integrable structure and is compatible with it. We illustrate this method on various integrable and non-integrable chains, and deduce some general results. In particular, we fermionize XXC spin-chains and study their symmetries. Fermionic realizations of certain Lie algebras and superalgebras appear naturally as symmetries of some models. We also fermionize recently obtained Hubbard models, and obtain for the first time multispecies analogues of the Hubbard model, in their fermionic form. We comment on the conflict between symmetry enhancement and integrability of these models. Finally, the fermionic versions of the non-integrable spin-1 and spin- {3}/{2} Heisenberg chains are obtained.
Open fermionic quantum systems
Artacho, E.; Falicov, L.M. Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 )
1993-01-15
A method to treat a quantum system in interaction with a fermionic reservoir is presented. Its most important feature is that the dynamics of the exchange of particles between the system and the reservoir is explicitly included via an effective interaction term in the Hamiltonian. This feature gives rise to fluctuations in the total number of particles in the system. The system is to be considered in its full structure, whereas the reservoir is described only in an effective way, as a source of particles characterized by a small set of parameters. Possible applications include surfaces, molecular clusters, and defects in solids, in particular in highly correlated electronic materials. Four examples are presented: a tight-binding model for an adsorbate on the surface of a one-dimensional lattice, the Anderson model of a magnetic impurity in a metal, a two-orbital impurity with interorbital hybridization (intermediate-valence center), and a two-orbital impurity with interorbital repulsive interactions.
Visualization and Evolution of the Scientific Structure of Fuzzy Sets Research in Spain
ERIC Educational Resources Information Center
Lopez-Herrera, A. G.; Cobo, M. J.; Herrera-Viedma, E.; Herrera, F.; Bailon-Moreno, R.; Jimenez-Contreras, E.
2009-01-01
Introduction: Presents the first bibliometric study on the evolution of the fuzzy sets theory field. It is specially focused on the research carried out by the Spanish community. Method. The CoPalRed software, for network analysis, and the co-word analysis technique are used. Analysis: Bibliometric maps showing the main associations among the…
Stereoscopy in Static Scientific Imagery in an Informal Education Setting: Does It Matter?
ERIC Educational Resources Information Center
Price, C. Aaron; Lee, H.-S.; Malatesta, K.
2014-01-01
Stereoscopic technology (3D) is rapidly becoming ubiquitous across research, entertainment and informal educational settings. Children of today may grow up never knowing a time when movies, television and video games were not available stereoscopically. Despite this rapid expansion, the field's understanding of the impact of stereoscopic…
An Analysis Framework Addressing the Scale and Legibility of Large Scientific Data Sets
Childs, H R
2006-11-20
Much of the previous work in the large data visualization area has solely focused on handling the scale of the data. This task is clearly a great challenge and necessary, but it is not sufficient. Applying standard visualization techniques to large scale data sets often creates complicated pictures where meaningful trends are lost. A second challenge, then, is to also provide algorithms that simplify what an analyst must understand, using either visual or quantitative means. This challenge can be summarized as improving the legibility or reducing the complexity of massive data sets. Fully meeting both of these challenges is the work of many, many PhD dissertations. In this dissertation, we describe some new techniques to address both the scale and legibility challenges, in hope of contributing to the larger solution. In addition to our assumption of simultaneously addressing both scale and legibility, we add an additional requirement that the solutions considered fit well within an interoperable framework for diverse algorithms, because a large suite of algorithms is often necessary to fully understand complex data sets. For scale, we present a general architecture for handling large data, as well as details of a contract-based system for integrating advanced optimizations into a data flow network design. We also describe techniques for volume rendering and performing comparisons at the extreme scale. For legibility, we present several techniques. Most noteworthy are equivalence class functions, a technique to drive visualizations using statistical methods, and line-scan based techniques for characterizing shape.
NASA Astrophysics Data System (ADS)
Raker, Jeffrey R.
Reform efforts in science education have called for instructional methods and resources that mirror the practice of science. Little research and design methods have been documented in the literature for designing such materials. The purpose of this study was to develop problems sets for sophomore-level organic chemistry instruction. This research adapted an instructional design methodology from the science education literature for the creation of new curricular problem sets. The first phase of this study was to establish an understanding of current curricular problems in sophomore-level organic chemistry instruction. A sample of 792 problems was collected from four organic chemistry courses. These problems were assessed using three literature reported problem typologies. Two of these problem typologies have previously been used to understand general chemistry problems; comparisons between general and organic chemistry problems were thus made. Data from this phase was used to develop a set of five problems for practicing organic chemists. The second phase of this study was to explore practicing organic chemists' experiences solving problems in the context of organic synthesis research. Eight practicing organic chemists were interviewed and asked to solve two to three of the problems developed in phase one of this research. These participants spoke of three problem types: project level, synthetic planning, and day-to-day. Three knowledge types (internal knowledge, knowledgeable others, and literature) were used in solving these problems in research practice and in the developed problems. A set of guiding factors and implications were derived from this data and the chemistry education literature for the conversion of the problems for practicing chemists to problems for undergraduate students. A subsequent conversion process for the five problems occurred. The third, and last phase, of this study was to explore undergraduate students' experiences solving problems in
NASA Astrophysics Data System (ADS)
Zeman, Antonín; Šmíd, Michal; Havelcová, Martina; Coufalová, Lucie; Kučková, Štěpánka; Velčovská, Martina; Hynek, Radovan
2013-11-01
Degenerative aortic stenosis has become a common and dangerous disease in recent decades. This disease leads to the mineralization of aortic valves, their gradual thickening and loss of functionality. We studied the detailed assessment of the proportion and composition of inorganic and organic components in the ossified aortic valve, using a set of analytical methods applied in science: polarized light microscopy, scanning electron microscopy, X-ray fluorescence, X-ray diffraction, gas chromatography/mass spectrometry and liquid chromatography-tandem mass spectrometry. The sample valves showed the occurrence of phosphorus and calcium in the form of phosphate and calcium carbonate, hydroxyapatite, fluorapatite and hydroxy-fluorapatite, with varying content of inorganic components from 65 to 90 wt%, and with phased development of degenerative disability. The outer layers of the plaque contained an organic component with peptide bonds, fatty acids, proteins and cholesterol. The results show a correlation between the formation of fluorapatite in aortic valves and in other parts of the human bodies, associated with the formation of bones.
Bold Diagrammatic Monte Carlo for Fermionic and Fermionized Systems
NASA Astrophysics Data System (ADS)
Svistunov, Boris
2013-03-01
In three different fermionic cases--repulsive Hubbard model, resonant fermions, and fermionized spins-1/2 (on triangular lattice)--we observe the phenomenon of sign blessing: Feynman diagrammatic series features finite convergence radius despite factorial growth of the number of diagrams with diagram order. Bold diagrammatic Monte Carlo technique allows us to sample millions of skeleton Feynman diagrams. With the universal fermionization trick we can fermionize essentially any (bosonic, spin, mixed, etc.) lattice system. The combination of fermionization and Bold diagrammatic Monte Carlo yields a universal first-principle approach to strongly correlated lattice systems, provided the sign blessing is a generic fermionic phenomenon. Supported by NSF and DARPA
NASA Astrophysics Data System (ADS)
Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran
2016-03-01
We study the conformal bootstrap for a 4-point function of fermions < ψψψψ> in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ × ψ OPE, and also on the central charge C T . We observe features in our bounds that coincide with scaling dimensions in the GrossNeveu models at large N . We also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.
NASA Astrophysics Data System (ADS)
Weiner, Richard M.
2010-05-01
It is conjectured that all known fermions are topological solitons. This could explain the non-observation of bosonic leptons and baryons and provide a physical mechanism for the Pauli exclusion principle.
Canonical gravity with fermions
Bojowald, Martin; Das, Rupam
2008-09-15
Canonical gravity in real Ashtekar-Barbero variables is generalized to allow for fermionic matter. The resulting torsion changes several expressions in Holst's original vacuum analysis, which are summarized here. This in turn requires adaptations to the known loop quantization of gravity coupled to fermions, which is discussed on the basis of the classical analysis. As a result, parity invariance is not manifestly realized in loop quantum gravity.
A geometrical formulation of fermionic integrable systems
Das, A.; Huang, W.; Roy, S. )
1991-10-01
A fermionic Hamiltonian system is formulated on a supermanifold. It is shown that if the system possesses a bi-Hamiltonian structure, one can naturally define a Lax equation associated with a (1,1) tensor on this supermanifold and this allows one to construct a set of conserved quantities. Furthermore, if the corresponding Nijenhuis tensor vanishes, it is shown that all these conserved quantities would be in involution which is a sufficient condition for integrability of the system. The fermionic extension of the KdV equation with a bi-Hamiltonian structure within this geometrical approach is studied.
NASA Astrophysics Data System (ADS)
Marino, Eduardo
The electron, discovered by Thomson by the end of the nineteenth century, was the first experimentally observed particle. The Weyl fermion, though theoretically predicted since a long time, was observed in a condensed matter environment in an experiment reported only a few weeks ago. Is there any linking thread connecting the first and the last observed fermion (quasi)particles? The answer is positive. By generalizing the method known as bosonization, the first time in its full complete form, for a spacetime with 3+1 dimensions, we are able to show that both electrons and Weyl fermions can be expressed in terms of the same boson field, namely the Kalb-Ramond anti-symmetric tensor gauge field. The bosonized form of the Weyl chiral currents lead to the angle-dependent magneto-conductance behavior observed in these systems.
Grossman, Yuval; Harnik, Roni; Perez, Gilad; Schwartz, MatthewD.; Surujon, Ze'ev
2004-07-30
The observed flavor structure of the standard model arises naturally in ''split fermion'' models which localize fermions at different places in an extra dimension. It has, until now, been assumed that the bulk masses for such fermions can be chosen to be flavor diagonal simultaneously at every point in the extra dimension, with all the flavor violation coming from the Yukawa couplings to the Higgs. We consider the more natural possibility in which the bulk masses cannot be simultaneously diagonalized, that is, that they are twisted in flavor space. We show that, in general, this does not disturb the natural generation of hierarchies in the flavor parameters. Moreover, it is conceivable that all the flavor mixing and CP-violation in the standard model may come only from twisting, with the five-dimensional Yukawa couplings taken to be universal.
Grossman, Y
2004-07-24
The observed flavor structure of the standard model arises naturally in ''split fermion'' models which localize fermions at different places in an extra dimension. It has, until now, been assumed that the bulk masses for such fermions can be chosen to be flavor diagonal simultaneously at every point in the extra dimension, with all the flavor violation coming from the Yukawa couplings to the Higgs. We consider the more natural possibility in which the bulk masses cannot be simultaneously diagonalized, that is, that they are twisted in flavor space. We show that, in general, this does not disturb the natural generation of hierarchies in the flavor parameters. Moreover, it is conceivable that all the flavor mixing and CP-violation in the standard model may come only from twisting, with the five-dimensional Yukawa couplings taken to be universal.
Technology Transfer Automated Retrieval System (TEKTRAN)
On September 11-14, 2012, the US Environmental Protection Agency convened a public meeting of the FIFRA Scientific Advisory Panel (SAP) to address scientific issues associated with the Office of Pesticides Program’s (OPP) proposed “Pollinator Risk Assessment Framework”. Several sources have reporte...
s-Wave collisional frequency shift of a fermion clock.
Hazlett, Eric L; Zhang, Yi; Stites, Ronald W; Gibble, Kurt; O'Hara, Kenneth M
2013-04-19
We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, θ(1). The fermion shift instead depends strongly on the second pulse area θ(2). It allows the shift to be canceled, nominally at θ(2)=π/2, but correlations perturb the null to slightly larger θ(2). The frequency shift is relevant for optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally larger at optical frequencies. PMID:23679589
NASA Technical Reports Server (NTRS)
Schofield, Norman J. (Editor); Parthasarathy, R. (Editor); Hills, H. Kent (Editor)
1988-01-01
The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of data sets from geostationary and high altitude scientific spacecraft and investigations. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also provided.
NASA Technical Reports Server (NTRS)
Jackson, John E. (Editor); Horowitz, Richard (Editor)
1986-01-01
The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of data sets from low and medium altitude scientific spacecraft and investigations. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also provided.
Hadron Properties with FLIC Fermions
James Zanotti; Wolodymyr Melnitchouk; Anthony Williams; J Zhang
2003-07-01
The Fat-Link Irrelevant Clover (FLIC) fermion action provides a new form of nonperturbative O(a)-improvement in lattice fermion actions offering near continuum results at finite lattice spacing. It provides computationally inexpensive access to the light quark mass regime of QCD where chiral nonanalytic behavior associated with Goldstone bosons is revealed. The motivation and formulation of FLIC fermions, its excellent scaling properties and its low-lying hadron mass phenomenology are presented.
The Set Point Theory of Well-Being Has Serious Flaws: On the Eve of a Scientific Revolution?
ERIC Educational Resources Information Center
Headey, Bruce
2010-01-01
Set-point theory is the main research paradigm in the field of subjective well-being (SWB). It has been extended and refined for 30 years to take in new results. The central plank of the theory is that adult set-points do not change, except temporarily in the face of major life events. There was always some "discordant data," including evidence…
Nucleon Resonances from FLIC Fermions
Derek Leinweber; J. Hedditch; Wally Melnitchouk; Anthony Williams
2003-01-01
The Fat Link Irrelevant Glover (FL1C) fermion action and its associated phenomenology is described. The scaling analysis indicates FLIC fermions provide a new form of nonperturbative O(a) improvement where near-continuum results are obtained at finite lattice spacing spin-1/2 and spin-3/2 , even and odd parity nucleon resonances are investigated.
Unconventional superconductivity in heavy-fermion compounds
White, B. D.; Thompson, J. D.; Maple, M. B.
2015-02-27
Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion com- pounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates andmore » iron-based superconductors. Lastly, we conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.« less
Unconventional superconductivity in heavy-fermion compounds
White, B. D.; Thompson, J. D.; Maple, M. B.
2015-02-27
Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion com- pounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates and iron-based superconductors. Lastly, we conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.
Mather, M. E.; Parrish, D.L.; Dettmers, J.M.
2008-01-01
In the last 25 years, the number and scope of fish-related journals have changed. New and existing journals are increasingly specialized. Journals that are read and cited are changing because of differential accessibility via electronic databases. In this review, we examine shifts in numbers and foci of existing fish-related journals. We ask how these fish-related metrics differ across type of application, ecological system, taxa, and discipline. Although many journals overlap to some extent in content, there are distinct groups of journals for authors to consider. By systematically reviewing the focus of an individual manuscript, comparing it to the suite of journals available and examining the audience for the manuscript, we believe that authors can make informed decisions about which journals are most suitable for their work. Our goal here is to help authors find relevant journals and deliver scientific publications to the appropriate readership.
ERIC Educational Resources Information Center
Graves, Chiron; Rutherford, Sandra
2012-01-01
Educational research focused on questioning techniques used in classroom settings is quite extensive. However, research regarding a teacher's ability to generate research questions is virtually nonexistent. Posing research or "testable" questions is a key component of inquiry-based instruction, and teachers must be able to both generate these…
Technology Transfer Automated Retrieval System (TEKTRAN)
The purpose of this statement is to provide an overview of new and emerging tools and strategies for discussing weight and assisting overweight and obese patients. Only tools and strategies that can be used practically in busy ambulatory settings are included. The goal is to provide clinicians with ...
EDITORIAL: International Conference on Finite Fermionic Systems: Nilsson Model 50 Years
NASA Astrophysics Data System (ADS)
2006-06-01
In 1955 Sven Gösta Nilsson published the paper `Binding States of Individual Nucleons in Strongly Deformed Nuclei'. This eminent work has been crucial for the understanding of the structure of deformed atomic nuclei. Moreover, the so-called Nilsson model has been widely used for the description of other types of finite systems of fermions such as quantum dots and cold fermionic atoms. During one week in June 2005 we celebrated in Lund the 50th anniversary of the Nilsson model with the International Conference on Finite Fermionic Systems - Nilsson Model 50 Years. With the historical view in mind, the conference focused on present and future problems in nuclear structure physics as well as on the physics of other types of finite Fermi systems. As a background to the recent developments Nobel Laureate Ben Mottelson presented a recollection of early applications and achievements of the Nilsson model in the first talk of the conference, including a personal view of Sven Gösta Nilsson. We are particularly pleased that this contribution could be included in these proceedings. The scientific programme was structured according to the following subjects: Shell structure and deformations The heaviest elements and beyond Nuclei far from stability Pairing correlations Nuclear spectroscopy: large deformations Nuclear spectroscopy: rotational states Order and chaos Cold fermionic atoms Quantum dots Many new and interesting results were presented in the 15 invited talks, 30 oral contributions, and in the 33 papers of the poster sessions. The present volume of Physica Scripta contains most of the talks, as well as the short contributions of the posters. We thank the speakers and all participants who actively contributed to give this memorable conference a very high scientific level in the presented contributions, as well as in numerous discussions inside and outside the sessions. We also thank the international advisory committee for their invaluable work in helping us setting up
Unlocking fermionic mode entanglement
NASA Astrophysics Data System (ADS)
Friis, Nicolai
2016-06-01
Aside from other puzzling features of entanglement, it has been debated whether a physically meaningful notion of entanglement requires two (or more) particles as carriers of the correlated degrees-of-freedom, or if a single particle could be considered to be entangled as well. While the usefulness of single-boson entanglement has been demonstrated some time ago, the restrictions of superselection rules have previously thwarted attempts at similar arguments for single fermions. In Dasenbrook et al (2016 New J. Phys. 18 043036) this obstacle is overcome. The authors propose a scheme for a Bell test on two copies of single-electron states whose entanglement is individually not accessible. The discussed scheme, which makes use of recent progress in electronic quantum optics, provides an experimentally viable and theoretically unambiguous way to assert that certain single-electron states can be considered to be entangled.
Dynamical symmetries for fermions
Guidry, M.
1989-01-01
An introduction is given to the Fermion Dynamical Symmetry Model (FDSM). The analytical symmetry limits of the model are then applied to the calculation of physical quantities such as ground-state masses and B(E{sub 2}) values in heavy nuclei. These comparisons with data provide strong support for a new principle of collective motion, the Dynamical Pauli Effect, and suggest that dynamical symmetries which properly account for the pauli principle are much more persistent in nuclear structure than the corresponding boson symmetries. Finally, we present an assessment of criticisms which have been voiced concerning the FDSM, and a discussion of new phenomena and exotic spectroscopy'' which may be suggested by the model. 14 refs., 8 figs., 4 tabs.
FLIC Fermions and Hadron Phenomenology
D. Leinweber; J.N. Hedditch; W. Melnitchouk; A.W. Thomas; A.G. Williams; R.D. Young; J.M. Zanotti; J.B. Zhang
2002-06-01
A pedagogical overview of the formulation of the Fat Link Irrelevant Clover (FLIC) fermion action and its associated phenomenology is described. The scaling analysis indicates FLIC fermions provide a new form of nonperturbative order (a) improvement where near-continuum results are obtained at finite lattice spacing. Spin-1/2 and spin-3/2, even and odd parity baryon resonances are investigated in quenched QCD, where the nature of the Roper resonance and Lambda (1405) are of particular interest. FLIC fermions allow efficient access to the light quark-mass regime, where evidence of chiral nonanalytic behavior in the Delta mass is observed.
NASA Astrophysics Data System (ADS)
Hofmeister, Richard; Lemmen, Carsten; Nasermoaddeli, Hassan; Klingbeil, Knut; Wirtz, Kai
2015-04-01
Data and models for describing coastal systems span a diversity of disciplines, communities, ecosystems, regions and techniques. Previous attempts of unifying data exchange, coupling interfaces, or metadata information have not been successful. We introduce the new Modular System for Shelves and Coasts (MOSSCO, http://www.mossco.de), a novel coupling framework that enables the integration of a diverse array of models and data from different disciplines relating to coastal research. In the MOSSCO concept, the integrating framework imposes very few restrictions on contributed data or models; in fact, there is no distinction made between data and models. The few requirements are: (1) principle coupleability, i.e. access to I/O and timing information in submodels, which has recently been referred to as the Basic Model Interface (BMI) (2) open source/open data access and licencing and (3) communication of metadata, such as spatiotemporal information, naming conventions, and physical units. These requirements suffice to integrate different models and data sets into the MOSSCO infrastructure and subsequently built a modular integrated modeling tool that can span a diversity of processes and domains. We demonstrate how diverse coastal system constituents were integrated into this modular framework and how we deal with the diverging development of constituent data sets and models at external institutions. Finally, we show results from simulations with the fully coupled system using OGC WebServices in the WiMo geoportal (http://kofserver3.hzg.de/wimo), from where stakeholders can view the simulation results for further dissemination.
AdS{sub 5} black holes with fermionic hair
Burrington, Benjamin A.; Liu, James T.; Sabra, W. A.
2005-05-15
The study of new Bogomol'nyi-Prasad-Sommerfield (BPS) objects in AdS{sub 5} has led to a deeper understanding of AdS/CFT. To help complete this picture, and to fully explore the consequences of the supersymmetry algebra, it is also important to obtain new solutions with bulk fermions turned on. In this paper we construct superpartners of the 1/2 BPS black hole in AdS{sub 5} using a natural set of fermion zero modes. We demonstrate that these superpartners, carrying fermionic hair, have conserved charges differing from the original bosonic counterpart. To do so, we find the R-charge and dipole moment of the new system, as well as the mass and angular momentum, defined through the boundary stress tensor. The complete set of superpartners fits nicely into a chiral representation of AdS{sub 5} supersymmetry, and the spinning solutions have the expected gyromagnetic ratio, g=1.
Observing remnants by fermions' tunneling
Chen, D.Y.; Wu, H.W.; Yang, H. E-mail: iverwu@uestc.edu.cn
2014-03-01
The standard Hawking formula predicts the complete evaporation of black holes. In this paper, we introduce effects of quantum gravity into fermions' tunneling from Reissner-Nordstrom and Kerr black holes. The quantum gravity effects slow down the increase of Hawking temperatures. This property naturally leads to a residue mass in black hole evaporation. The corrected temperatures are affected by the quantum numbers of emitted fermions. Meanwhile, the temperature of the Kerr black hole is a function of θ due to the rotation.
Standard electromagnetically driven cosmology coupled with fermionic source
Mello, M. M. C.; Klippert, R.
2015-03-10
Dirac fermions and electromagnetic fields are considered as the source of gravitation in the framework of standard Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology. It is shown that all solutions for the scale-factor a(t) are non-singular, provided the cosmological constant Λ is set to be less than the positive inverse of a quantum scale.
Fermionic corrections to fluid dynamics from BTZ black hole
NASA Astrophysics Data System (ADS)
Gentile, L. G. C.; Grassi, P. A.; Mezzalira, A.
2015-11-01
We reconstruct the complete fermionic orbit of the non-extremal BTZ black hole by acting with finite supersymmetry transformations. The solution satisfies the exact supergravity equations of motion to all orders in the fermonic expansion and the final result is given in terms of fermionic bilinears. By fluid/gravity correspondence, we derive linearized Navier-Stokes equations and a set of new differential equations from Rarita-Schwinger equation. We compute the boundary energy-momentum tensor and we interpret the result as a perfect fluid with a modified definition of fluid velocity. Finally, we derive the modified expression for the entropy of the black hole in terms of the fermionic bilinears.
Staggered fermions, zero modes, and flavor-singlet mesons
Donald, Gordon C; Davies, Christine T.H.; Follana, Eduardo; Kronfeld, Andreas S.
2011-09-12
We examine the taste structure of eigenvectors of the staggered-fermion Dirac operator. We derive a set of conditions on the eigenvectors of modes with small eigenvalues (near-zero modes), such that staggered fermions reproduce the 't Hooft vertex in the continuum limit. We also show that, assuming these conditions, the correlators of flavor-singlet mesons are free of contributions singular in 1/m, where m is the quark mass. This conclusion holds also when a single flavor of sea quark is represented by the fourth root of the staggered-fermion determinant. We then test numerically, using the HISQ action, whether these conditions hold on realistic lattice gauge fields. We find that the needed structure does indeed emerge.
Staggered fermions, zero modes, and flavor-singlet mesons
Donald, Gordon C; Davies, Christine T.H.; Follana, Eduardo; Kronfeld, Andreas S.
2011-09-12
We examine the taste structure of eigenvectors of the staggered-fermion Dirac operator. We derive a set of conditions on the eigenvectors of modes with small eigenvalues (near-zero modes), such that staggered fermions reproduce the 't Hooft vertex in the continuum limit. We also show that, assuming these conditions, the correlators of flavor-singlet mesons are free of contributions singular in 1/m, where m is the quark mass. This conclusion holds also when a single flavor of sea quark is represented by the fourth root of the staggered-fermion determinant. We then test numerically, using the HISQ action, whether these conditions hold onmore » realistic lattice gauge fields. We find that the needed structure does indeed emerge.« less
Fermion localization on thick branes
Melfo, Alejandra; Pantoja, Nelson; Tempo, Jose David
2006-02-15
We consider chiral fermion confinement in scalar thick branes, which are known to localize gravity, coupled through a Yukawa term. The conditions for the confinement and their behavior in the thin-wall limit are found for various different BPS branes, including double walls and branes interpolating between different AdS{sub 5} spacetimes. We show that only one massless chiral mode is localized in all these walls, whenever the wall thickness is keep finite. We also show that, independently of wall's thickness, chiral fermionic modes cannot be localized in dS{sub 4} walls embedded in a M{sub 5} spacetime. Finally, massive fermions in double wall spacetimes are also investigated. We find that, besides the massless chiral mode localization, these double walls support quasilocalized massive modes of both chiralities.
Fermion production during and after axion inflation
Adshead, Peter; Sfakianakis, Evangelos I.
2015-11-11
We study derivatively coupled fermions in axion-driven inflation, specifically m{sub ϕ}{sup 2}ϕ{sup 2} and monodromy inflation, and calculate particle production during the inflationary epoch and the post-inflationary axion oscillations. During inflation, the rolling axion acts as an effective chemical potential for helicity which biases the gravitational production of one fermion helicity over the other. This mechanism allows for efficient gravitational production of heavy fermion states that would otherwise be highly suppressed. Following inflation, the axion oscillates and fermions with both helicities are produced as the effective frequency of the fermion field changes non-adiabatically. For certain values of the fermion mass and axion-fermion coupling strength, the two helicity states are produced asymmetrically, resulting in unequal number-densities of left- and right-helicity fermions.
Fermionic influence on inflationary fluctuations
NASA Astrophysics Data System (ADS)
Boyanovsky, Daniel
2016-04-01
Motivated by apparent persistent large scale anomalies in the cosmic microwave background we study the influence of fermionic degrees of freedom on the dynamics of inflaton fluctuations as a possible source of violations of (nearly) scale invariance on cosmological scales. We obtain the nonequilibrium effective action of an inflaton-like scalar field with Yukawa interactions (YD ,M) to light fermionic degrees of freedom both for Dirac and Majorana fields in de Sitter space-time. The effective action leads to Langevin equations of motion for the fluctuations of the inflaton-like field, with self-energy corrections and a stochastic Gaussian noise. We solve the Langevin equation in the super-Hubble limit implementing a dynamical renormalization group resummation. For a nearly massless inflaton its power spectrum of super-Hubble fluctuations is enhanced, P (k ;η )=(H/2 π )2eγt[-k η ] with γt[-k η ]=1/6 π2 [∑i =1 NDYi,D 2+2 ∑j =1 NMYj,M 2]{ln2[-k η ]-2 ln [-k η ]ln [-k η0]} for ND Dirac and NM Majorana fermions, and η0 is the renormalization scale at which the inflaton mass vanishes. The full power spectrum is shown to be renormalization group invariant. These corrections to the super-Hubble power spectrum entail a violation of scale invariance as a consequence of the coupling to the fermionic fields. The effective action is argued to be exact in the limit of a large number of fermionic fields. A cancellation between the enhancement from fermionic degrees of freedom and suppression from light scalar degrees of freedom conformally coupled to gravity suggests the possibility of a finely tuned supersymmetry among these fields.
Fermionic composite models from complementarity
NASA Astrophysics Data System (ADS)
Bordi, F.; Casalbuoni, R.; Dominici, D.; Gatto, R.
1982-08-01
Composite models for (in principle massless) quarks and leptons without fundamental scalars are constructed with the aim of providing for fermionic realizations of models which include elementary bosons (by Abbott and Farhi, Casalbuoni and Gatto and Barbieri, Mohapatra and Masiero). The models use one confining unitary (subcolor) group (with left-handed fermions in the fundamental, in its conjugate, and either in the adjoint, or in the symmetric, or in the antisymmetric representation of subcolor) or two confining groups. Families may arise from discrete symmetries.
NASA Astrophysics Data System (ADS)
Colangeli, Matteo; Pezzotti, Federica; Pulvirenti, Mario
2015-05-01
We introduce a stochastic N-particle system and show that, as N → ∞, an effective description ruled by the homogeneous fermionic Uehling-Uhlenbeck equation is recovered. The particle model we consider is the same as the Kac model for the homogeneous Boltzmann equation with an additional exclusion constraint taking into account the Pauli Exclusion Principle.
Searches for Fourth Generation Fermions
Ivanov, A.; /Fermilab
2011-09-01
We present the results from searches for fourth generation fermions performed using data samples collected by the CDF II and D0 Detectors at the Fermilab Tevatron p{bar p} collider. Many of these results represent the most stringent 95% C. L. limits on masses of new fermions to-date. A fourth chiral generation of massive fermions with the same quantum numbers as the known fermions is one of the simplest extensions of the SM with three generations. The fourth generation is predicted in a number of theories, and although historically have been considered disfavored, stands in agreement with electroweak precision data. To avoid Z {yields} {nu}{bar {nu}} constraint from LEP I a fourth generation neutrino {nu}{sub 4} must be heavy: m({nu}{sub 4}) > m{sub Z}/2, where m{sub Z} is the mass of Z boson, and to avoid LEP II bounds a fourth generation charged lepton {ell}{sub 4} must have m({ell}{sub 4}) > 101 GeV/c{sup 2}. At the same time due to sizeable radiative corrections masses of fourth generation fermions cannot be much higher the current lower bounds and masses of new heavy quarks t' and b' should be in the range of a few hundred GeV/c{sup 2}. In the four-generation model the present bounds on the Higgs are relaxed: the Higgs mass could be as large as 1 TeV/c{sup 2}. Furthermore, the CP violation is significantly enhanced to the magnitude that might account for the baryon asymmetry in the Universe. Additional chiral fermion families can also be accommodated in supersymmetric two-Higgs-doublet extensions of the SM with equivalent effect on the precision fit to the Higgs mass. Another possibility is heavy exotic quarks with vector couplings to the W boson Contributions to radiative corrections from such quarks with mass M decouple as 1/M{sup 2} and easily evade all experimental constraints. At the Tevatron p{bar p} collider 4-th generation chiral or vector-like quarks can be either produced strongly in pairs or singly via electroweak production, where the latter can be
Technology Transfer Automated Retrieval System (TEKTRAN)
On December 2-4, 2014, the US Environmental Protection Agency convened a public meeting of the FIFRA Scientific Advisory Panel (SAP) to address scientific issues associated with the agency’s “Integrated Endocrine Bioactivity and Exposure-Based Prioritization and Screening” methods. EPA is proposing ...
Radiative fermion masses in local D-brane models
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Krippendorf, Sven; Maharana, Anshuman; Quevedo, Fernando
2011-05-01
In the context of D-brane model building, we present a realistic framework for generating fermion masses that are forbidden by global symmetries. We show that the string theoretical Large volume scenario circumvents the standard lore that fermion masses generated by loop effects are too small in generic gravity mediated scenarios. We argue that the fact that in toric singularity models, the up quark masses have always a zero eigenvalue, corresponding to the lightest generation, is due to the presence of approximate global symmetries that we explicitly identify in del Pezzo singularities. These symmetries are broken by global effects and therefore proportional to inverse powers of the volume. We estimate the generic size of radiative corrections to fermion masses in different phenomenological manifestations of the Large volume scenario. Concrete realizations in terms of flavor violating soft-terms are estimated and contrasted with current bounds on flavour changing neutral currents. Contributions from generic extra Higgs-like fields set bounds on their masses close to the GUT scale to produce realistic fermion masses.
Domain wall fermion quenched spectroscopy
NASA Astrophysics Data System (ADS)
Malureanu, Catalin Ionut
We measure y and the hadron spectrum on quenched ensembles using the domain wall fermion formulation. For the first time a 1/mf behavior of y for small valence masses has been observed. Our measurements of y on two different volumes of 83 x 32 and 163 x 32 at β = 5.85 suggest the behavior goes away on large enough volumes. Extensive spectrum calculations were done on 8 3 x 32 lattices at β = 5.7 and 5.85 corresponding roughly to a box size of 1.6 fm and 1.0 fm respectively. We have investigated five values of the extent of the fifth dimension Ls = 10, 16, 24, 32 and 48 with valence masses in the range 0.02 to 0.2 for the β = 5.7 ensemble and two values of Ls = 10 and 16 with valence masses in the range 0.02 to 0.08 for the β = 5.85 ensemble. Our pion remains massive in the infinite Ls extrapolation. This may be a finite volume effect. The nucleon to rho mass ratio stays constant at 1.4(1). Scaling violations for domain wall fermions are smaller roughly by a factor of four compared to the scaling violations in similar calculations done with staggered fermions.
Superdeformations and fermion dynamical symmetries
Wu, Cheng-Li . Dept. of Physics and Atmospheric Science Tennessee Univ., Knoxville, TN . Dept. of Physics and Astronomy Joint Inst. for Heavy Ion Research, Oak Ridge, TN )
1990-01-01
In this talk, I will present a link between nuclear collective motions and their underlying fermion dynamical symmetries. In particular, I will focus on the microscopic understanding of deformations. It is shown that the SU{sub 3} of the one major shell fermion dynamical symmetry model (FDSM) is responsible for the physics of low and high spins in normal deformation. For the recently observed phenomena of superdeformation, the physics of the problem dictates a generalization to a supershell structure (SFDSM), which also has an SU{sub 3} fermion dynamical symmetry. Many recently discovered feature of superdeformation are found to be inherent in such an SU{sub 3} symmetry. In both cases the dynamical Pauli effect plays a vital role. A particularly noteworthy discovery from this model is that the superdeformed ground band is not the usual unaligned band but the D-pair aligned (DPA) band, which sharply crosses the excited bands. The existence of such DPA band is a key point to understand many properties of superdeformation. Our studies also poses new experimental challenge. This is particularly interesting since there are now plans to build new and exciting {gamma}-ray detecting systems, like the GAMMASPHERE, which could provide answers to some of these challenges. 34 refs., 11 figs., 5 tabs.
Dephasing time of composite fermions
Lee, P.A.; Mucciolo, E.R.
1996-09-01
We study the dephasing of fermions interacting with a fluctuating transverse-gauge field. The divergence of the imaginary part of the fermion self-energy at finite temperatures is shown to result from a breakdown of Fermi{close_quote}s golden rule due to a faster than exponential decay in time. The strong dephasing affects experiments where phase coherence is probed. This result is used to describe the suppression of Shubnikov{endash}de Haas (SdH) oscillations of composite fermions (oscillations in the conductivity near the half-filled Landau level). We find that it is important to take into account both the effect of dephasing and the mass renormalization. We conclude that while it is possible to use the conventional theory to extract an effective mass from the temperature dependence of the SdH oscillations, the resulting effective mass differs from the {ital m}{sup {asterisk}} of the quasiparticle in Fermi-liquid theory. {copyright} {ital 1996 The American Physical Society.}
Light scattering of degenerate fermions
NASA Astrophysics Data System (ADS)
Aubin, S.; Leblanc, L. J.; Myrskog, S.; Extavour, M. H. T.; McKay, D.; Stummer, A.; Thywissen, J. H.
2006-05-01
We report on progress in measuring the suppression of resonant light scattering in a gas of degenerate fermions. A gas of trapped degenerate fermions is expected to exhibit narrower optical linewidths and longer excited state lifetimes than single atoms when the Fermi energy is larger than the photon recoil energy [1-3]. In this case, the number of available states into which a scattered atom can recoil is significantly reduced due to the filling of the Fermi sea. We produce a degenerate gas of 4x10^4 ultra-cold fermionic ^40K atoms by sympathetic cooling with bosonic ^87Rb in a micro-magnetic chip trap. The atoms can then be loaded into a tight dipole trap just above the surface of the chip and probed with a near resonance laser pulse. [1] Th. Busch, J. R. Anglin, J. I. Cirac, and P. Zoller, Europhys. Lett. 44, 1 (1998). [2] B. DeMarco and D. S. Jin, Phys. Rev. A 58, R4267 (1998). [3] J. Javanainen and J. Ruostekosky, Phys. Rev. A 52, 3033 (1995). Work supported by NSERC, CFI, OIT, Research Corporation, and PRO.
Issues in heavy fermions and in high-T c superconductive materials raised at this conference
NASA Astrophysics Data System (ADS)
Varma, C. M.
1991-05-01
In this closing session at the conference I would like, in the light of the presentations at this conference to briefly summarize the remarkable progress achieved in the heavy-fermion and heavy-fermion superconductivity problems, and point to what seem to me the principal problems remaining. The situation in the theory of high- Tc materials, on the face of it, appears much less bright. Unlike the heavy fermions, there is no agreement on what model represents the essentials of the problem. I believe, the difficulty in achieving a consensus here is only partly scientific. It is also sociological. I will paint a rather sanguine picture of the scientific developments there as well.
Fermionic thermocoherent state: Efficiency of electron transport
NASA Astrophysics Data System (ADS)
Karmakar, Anirban; Gangopadhyay, Gautam
2016-02-01
On the basis of the fermionic coherent state of Cahill and Glauber [Phys. Rev. A 59, 1538 (1999)], 10.1103/PhysRevA.59.1538, we have introduced here the fermionic thermocoherent state in terms of the quasiprobability distribution which shows the appropriate thermal and coherent limits as in the bosonic case or the Glauber-Lachs state. It is shown that the fermionic thermocoherent state can be realized as a displaced thermal state of fermions. Its relation with the fermionic displaced number state and the fermion-added coherent state are explored in the spirit of the bosonic case. We have investigated the nature of the average current and the suppression of noise due to the thermocoherent character of the source. The theory is applied to the problem of electronic conduction. A modification of the Landauer conductance formula is suggested which reflects the role of nonzero coherence of the source in electron transport.
NASA Astrophysics Data System (ADS)
Baisden, T. W.
2013-12-01
Setting limits on pollution is an inherently political process negotiated between stakeholders within society. Science has a critical, but not dominant role in setting environmental limits. Over the past 20 years, nations have had the opportunity to build on a period of major international successes, limiting ozone-depleting chemicals and sulphur emissions causing acid rain. The science and politics of solutions attempted during this time has become vastly more complicated, and the outcome has been disappointing: global greenhouse gas emissions remain at business-as-usual trajectories. It seems logical and timely to examine the landscape before forging onward. In a brief review of lessons learned from the perspective of earth-system science within New Zealand, I highlight key examples and opportunities for creating more promising way forward. Among the lessons are that small-scale limit setting can host important innovation, while collapses can occur when systems that are too-big-to-fail but lack critical pre-requisites. In this sense, implementation of cap-and-trade for water quality may represent the former, while the collapse of C prices highlight the latter. Of critical importance is the simple observation that perceived uncertainties must be brought within bounds that make decisions possible. The way in which system are framed scientifically can be of overarching significance. Cap and trade for nutrients in New Zealand catchments has enabled small-scale illustrations of how the system frame can be vital in successful policy. For example, the N budget of Lake Taupo is simplified by focusing on inputs to the land, while 100-year forcing equivalence still raises questions about managing climate change. Relationships between emissions and activity must be distilled based on sound science, in a manner simple and certain enough for people and businesses to meaningfully consider in decisions that are made every day. With trust becoming a major limiting factor in the
Cold collisions between boson or fermion molecules
Kajita, Masatoshi
2004-01-01
We theoretically investigate collisions between electrostatically trapped cold polar molecules and compare boson and fermion isotopes. Evaporative cooling seems possible for fermion molecules as the ratio of the collision loss cross section to the elastic collision cross section (R) gets smaller as the molecular temperature T lowers. With boson molecules, R gets larger as T lowers, which makes evaporative cooling difficult. The elastic collision cross section between fermion molecules can be larger than that for boson molecules with certain conditions.
Fermion back reaction and the sphaleron
Roberge, A. )
1994-02-15
Using a simple model, a new sphaleron solution which incorporates finite fermionic density effects is obtained. The main result is that the height of the potential barrier (sphaleron energy) decreases as the fermion density increases. This suggests that the rate of sphaleron-induced transitions increases when the fermionic density increases. However the rate increase is not expected to change significantly the predictions from the standard sphaleron-induced baryogenesis scenarios.
Light quark simulations with FLIC fermions
J.M. Zanotti; D.B. Leinweber; W. Melnitchouk; A.G. Williams; J.B. Zhang
2002-06-01
Hadron masses are calculated in quenched lattice QCD in order to probe the scaling behavior of a novel fat-link clover fermion action in which only the irrelevant operators of the fermion action are constructed using APE-smeared links. Light quark masses corresponding to an m{sub pi}/m{sub p} ratio of 0.35 are considered to assess the exceptional configuration problem of clover-fermion actions. This Fat-Link Irrelevant Clover (FLIC) fermion action provides scaling which is superior to mean-field improvement and offers advantages over nonperturbative improvement, including reduced exceptional configurations.
Aharonov-Bohm radiation of fermions
Chu Yizen; Mathur, Harsh; Vachaspati, Tanmay
2010-09-15
We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cutoff, suggesting strong emission at an energy scale comparable to the string energy scale.
Myers, Teresa A; Maibach, Edward; Peters, Ellen; Leiserowitz, Anthony
2015-01-01
Human-caused climate change is happening; nearly all climate scientists are convinced of this basic fact according to surveys of experts and reviews of the peer-reviewed literature. Yet, among the American public, there is widespread misunderstanding of this scientific consensus. In this paper, we report results from two experiments, conducted with national samples of American adults, that tested messages designed to convey the high level of agreement in the climate science community about human-caused climate change. The first experiment tested hypotheses about providing numeric versus non-numeric assertions concerning the level of scientific agreement. We found that numeric statements resulted in higher estimates of the scientific agreement. The second experiment tested the effect of eliciting respondents' estimates of scientific agreement prior to presenting them with a statement about the level of scientific agreement. Participants who estimated the level of agreement prior to being shown the corrective statement gave higher estimates of the scientific consensus than respondents who were not asked to estimate in advance, indicating that incorporating an "estimation and reveal" technique into public communication about scientific consensus may be effective. The interaction of messages with political ideology was also tested, and demonstrated that messages were approximately equally effective among liberals and conservatives. Implications for theory and practice are discussed. PMID:25812121
Myers, Teresa A.; Maibach, Edward; Peters, Ellen; Leiserowitz, Anthony
2015-01-01
Human-caused climate change is happening; nearly all climate scientists are convinced of this basic fact according to surveys of experts and reviews of the peer-reviewed literature. Yet, among the American public, there is widespread misunderstanding of this scientific consensus. In this paper, we report results from two experiments, conducted with national samples of American adults, that tested messages designed to convey the high level of agreement in the climate science community about human-caused climate change. The first experiment tested hypotheses about providing numeric versus non-numeric assertions concerning the level of scientific agreement. We found that numeric statements resulted in higher estimates of the scientific agreement. The second experiment tested the effect of eliciting respondents’ estimates of scientific agreement prior to presenting them with a statement about the level of scientific agreement. Participants who estimated the level of agreement prior to being shown the corrective statement gave higher estimates of the scientific consensus than respondents who were not asked to estimate in advance, indicating that incorporating an “estimation and reveal” technique into public communication about scientific consensus may be effective. The interaction of messages with political ideology was also tested, and demonstrated that messages were approximately equally effective among liberals and conservatives. Implications for theory and practice are discussed. PMID:25812121
ERIC Educational Resources Information Center
Shapero, Albert
This is a second report of a study of the use of scientific and technical information in industrial and nonprofit settings. It focuses on mapping the information-communication behavior of the engineering division of the Southwest Research Institute. Data include questionnaires, library records, travel records, telephone records, and contractual…
STOUT SMEARING FOR TWISTED FERMIONS.
SCHOLZ,W.; JANSEN, K.; McNEILE, C.; MONTVAY, I.; RICHARDS, C.; URBACH, C.; WENGER, U.
2007-07-30
The effect of Stout smearing is investigated in numerical simulations with twisted mass Wilson quarks. The phase transition near zero quark mass is studied on 12{sup 3} x 24, 16{sup 3} x 32 and 24{sup 3} x 48 lattices at lattice spacings a {approx_equal} 0.1-0.125 fm. The phase structure of Wilson fermions with twisted mass ({mu}) has been investigated in [1,2]. As it is explained there, the observed first order phase transition limits the minimal pion mass which can be reached in simulations at a given lattice spacing: m{sub k}{sup min} {approx_equal} {theta}(a). The phase structure is schematically depicted in the left panel of Fig. I . The phase transition can be observed in simulations with twisted mass fermions, for instance, as a ''jump'' or even metastabilities in the average plaquette value as a function of the hopping parameter ({kappa}). One possibility to weaken the phase transition and therefore allow for lighter pion masses at a given lattice spacing is to use an improved gauge action like the DBW2, Iwasaki, or tree-level Symanzik (tlSym) improved gauge action instead of the simple Wilson gauge action. This has been successfully demonstrated in [3,4,5]. Here we report on our attempts to use a smeared gauge field in the fermion lattice Dirac operator to further reduce the strength of the phase transition. This is relevant in simulations with N{sub f} = 2 + 1 + 1 (u,d,s,c) quark flavors [6] where the first order phase transition becomes stronger compared to N{sub f} = 2 simulations. The main impact of the above mentioned improved gauge actions on the gauge fields occurring in simulations is to suppress short range fluctuations (''dislocations'') and the associated ''exceptionally small'' eigenvalues of the fermion matrix. The same effect is expected from smearing the gauge field links in the fermion action. The cumulated effect of the improved gauge action and smeared links should allow for a smaller pion mass at a given lattice spacing and volume. Our
Paired States of Composite Fermions
NASA Astrophysics Data System (ADS)
Bonesteel, N. E.
2002-03-01
There is compelling theoretical evidence(R. Morf, Phys. Rev. Lett. 80), 1505 (1998). that the ν=5/2 fractional quantum Hall state is a Moore-Read state(G. Moore and N. Read, Nucl. Phys. B 360), 362 (1991). -- a state which can be viewed as a spin-polarized p-wave `superconductor' of composite fermions. The question remains, how can one test this hypothesis experimentally? To address this we have developed a semi-phenomenological description of this state in which the Halperin-Lee-Read(B.I. Halperin, P.A. Lee, and N. Read, Phys. Rev. B 47), 7312 (1993). theory of the half-filled Landau level is modified by adding a p-wave pairing interaction between composite fermions by hand. The electromagnetic response functions for the resulting mean-field superconducting state are then calculated and used in an RPA calculation of the physical electronic response. For a clean enough sample, and for q << k_f, the transverse electromagnetic response function for composite fermions is governed by type-II coherence factors and shows a `Hebel-Slichter'-like peak as a function of temperature for low enough frequency. The possibility (and potential difficulties) of observing this peak indirectly in surface-acoustic-wave propagation experiments will be discussed. The observation of such a coherence peak would provide strong evidence of BCS pairing in the 5/2 state. Work supported by US DOE Grant No. DE-FG02-97ER45639. Work done in collaboration with K.C. Foster (FSU) and S.H. Simon (Lucent). note
Fermion dipole moment and holography
NASA Astrophysics Data System (ADS)
Kulaxizi, Manuela; Rahman, Rakibur
2015-12-01
In the background of a charged AdS black hole, we consider a Dirac particle endowed with an arbitrary magnetic dipole moment. For non-zero charge and dipole coupling of the bulk fermion, we find that the dual boundary theory can be plagued with superluminal modes. Requiring consistency of the dual CFT amounts to constraining the strength of the dipole coupling by an upper bound. We briefly discuss the implications of our results for the physics of holographic non-Fermi liquids.
Fermionic Quantization of Hopf Solitons
NASA Astrophysics Data System (ADS)
Krusch, S.; Speight, J. M.
2006-06-01
In this paper we show how to quantize Hopf solitons using the Finkelstein-Rubinstein approach. Hopf solitons can be quantized as fermions if their Hopf charge is odd. Symmetries of classical minimal energy configurations induce loops in configuration space which give rise to constraints on the wave function. These constraints depend on whether the given loop is contractible. Our method is to exploit the relationship between the configuration spaces of the Faddeev-Hopf and Skyrme models provided by the Hopf fibration. We then use recent results in the Skyrme model to determine whether loops are contractible. We discuss possible quantum ground states up to Hopf charge Q=7.
Coulomb interactions and fermion condensation
Capstick, S.; Cutkosky, R.E.; Joensen, M.A. ); Wang, K.C. )
1990-08-15
The influence of the Coulomb interaction in states containing massless and flavorless fermion-antifermion pairs is studied, using a continuum formulation within the finite volume {ital S}{sup 3}. Several different forms for the Coulomb interaction are examined, including confining potentials as well as nonconfining potentials. The calculations show that if the interaction is strong enough, the Coulomb interaction leads to condensation of pairs, and that this condensation has a chiral character. The condensation does not depend on whether the interaction is confining. It is found that simplified variational approximations are not accurate enough for an adequate description of the states.
Superalgebra and fermion-boson symmetry
Miyazawa, Hironari
2010-01-01
Fermions and bosons are quite different kinds of particles, but it is possible to unify them in a supermultiplet, by introducing a new mathematical scheme called superalgebra. In this article we discuss the development of the concept of symmetry, starting from the rotational symmetry and finally arriving at this fermion-boson (FB) symmetry. PMID:20228617
Mass-induced transition in fermion number
Aragao de Carvalho, C.; Pureza, J. M.
1989-05-15
We show that if we increase the mass of fermions in interaction with a topological (kink) scalar background in 1+1 dimensions, the fractional fermion number of the system will eventually vanish. The transition is sharp and corresponds to the disappearance of localized states from the spectrum of a Dirac operator which is exactly solvable. Possible applications to different physical systems are discussed.
Quantum electrodynamics with complex fermion mass
McKellar, B.J.H. . School of Physics); Wu, D.D. . School of Physics Academia Sinica, Beijing, BJ . Inst. of High Energy Physics Superconducting Super Collider Lab., Dallas, TX )
1991-08-01
The quantum electrodynamics (QED) with a complex fermion mass -- that is, a fermion mass with a chiral phase -- is restudied, together with its chirally rotated version. We show how fake electric dipole moment can be obtained and how to avoid it. 10 refs.
Scientific Literacy: Whose Responsibility?
ERIC Educational Resources Information Center
Evans, Thomas P.
1970-01-01
Identifies various components of scientific literacy and characteristics of scientifically literate people. Discusses factors inhibiting scientific literacy. Suggested remedies: federal support for special programs, redesign of teacher education programs and science content courses at all levels, and setting up means of interpreting science to the…
Fermionic T-Duality a Snapshot Review
NASA Astrophysics Data System (ADS)
Ó Colgáin, Eoin
2012-11-01
Through a self-dual mapping of the geometry AdS5 ×S5, fermionic T-duality provides a beautiful geometric interpretation of hidden symmetries for scattering amplitudes in N = 4 super-Yang-Mills. Starting with Green-Schwarz sigma-models, we consolidate developments in this area into this small review. In particular, we discuss the translation of fermionic T-duality into the supergravity fields via pure spinor formalism and show that a general class of fermionic transformations can be identified directly in the supergravity. In addition to discussing fermionic T-duality for the geometry AdS4 × ℂP3, dual to N = 6 ABJM theory, we review work on other self-dual geometries. Finally, we present a short round-up of studies with a formal interest in fermionic T-duality.
Tunable Dirac Fermion Dynamics in Topological Insulators
NASA Astrophysics Data System (ADS)
Chen, Chaoyu; Xie, Zhuojin; Feng, Ya; Yi, Hemian; Liang, Aiji; He, Shaolong; Mou, Daixiang; He, Junfeng; Peng, Yingying; Liu, Xu; Liu, Yan; Zhao, Lin; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Yu, Li; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Zhou, X. J.
2013-08-01
Three-dimensional topological insulators are characterized by insulating bulk state and metallic surface state involving relativistic Dirac fermions which are responsible for exotic quantum phenomena and potential applications in spintronics and quantum computations. It is essential to understand how the Dirac fermions interact with other electrons, phonons and disorders. Here we report super-high resolution angle-resolved photoemission studies on the Dirac fermion dynamics in the prototypical Bi2(Te,Se)3 topological insulators. We have directly revealed signatures of the electron-phonon coupling and found that the electron-disorder interaction dominates the scattering process. The Dirac fermion dynamics in Bi2(Te3-xSex) topological insulators can be tuned by varying the composition, x, or by controlling the charge carriers. Our findings provide crucial information in understanding and engineering the electron dynamics of the Dirac fermions for fundamental studies and potential applications.
Fermion hierarchy from sfermion anarchy
Altmannshofer, Wolfgang; Frugiuele, Claudia; Harnik, Roni
2014-12-31
We present a framework to generate the hierarchical flavor structure of Standard Model quarks and leptons from loops of superpartners. The simplest model consists of the minimal supersymmetric standard model with tree level Yukawa couplings for the third generation only and anarchic squark and slepton mass matrices. Agreement with constraints from low energy flavor observables, in particular Kaon mixing, is obtained for supersymmetric particles with masses at the PeV scale or above. In our framework both the second and the first generation fermion masses are generated at 1-loop. Despite this, a novel mechanism generates a hierarchy among the first andmore » second generations without imposing a symmetry or small parameters. A second-to-first generation mass ratio of order 100 is typical. The minimal supersymmetric standard model thus includes all the necessary ingredients to realize a fermion spectrum that is qualitatively similar to observation, with hierarchical masses and mixing. The minimal framework produces only a few quantitative discrepancies with observation, most notably the muon mass is too low. Furthermore, we discuss simple modifications which resolve this and also investigate the compatibility of our model with gauge and Yukawa coupling Unification.« less
Fermion hierarchy from sfermion anarchy
NASA Astrophysics Data System (ADS)
Altmannshofer, Wolfgang; Frugiuele, Claudia; Harnik, Roni
2014-12-01
We present a framework to generate the hierarchical flavor structure of Standard Model quarks and leptons from loops of superpartners. The simplest model consists of the minimal supersymmetric standard model with tree level Yukawa couplings for the third generation only and anarchic squark and slepton mass matrices. Agreement with constraints from low energy flavor observables, in particular Kaon mixing, is obtained for supersymmetric particles with masses at the PeV scale or above. In our framework both the second and the first generation fermion masses are generated at 1-loop. Despite this, a novel mechanism generates a hierarchy among the first and second generations without imposing a symmetry or small parameters. A second-to-first generation mass ratio of order 100 is typical. The minimal supersymmetric standard model thus includes all the necessary ingredients to realize a fermion spectrum that is qualitatively similar to observation, with hierarchical masses and mixing. The minimal framework produces only a few quantitative discrepancies with observation, most notably the muon mass is too low. We discuss simple modifications which resolve this and also investigate the compatibility of our model with gauge and Yukawa coupling Unification.
Fermion hierarchy from sfermion anarchy
Altmannshofer, Wolfgang; Frugiuele, Claudia; Harnik, Roni
2014-12-31
We present a framework to generate the hierarchical flavor structure of Standard Model quarks and leptons from loops of superpartners. The simplest model consists of the minimal supersymmetric standard model with tree level Yukawa couplings for the third generation only and anarchic squark and slepton mass matrices. Agreement with constraints from low energy flavor observables, in particular Kaon mixing, is obtained for supersymmetric particles with masses at the PeV scale or above. In our framework both the second and the first generation fermion masses are generated at 1-loop. Despite this, a novel mechanism generates a hierarchy among the first and second generations without imposing a symmetry or small parameters. A second-to-first generation mass ratio of order 100 is typical. The minimal supersymmetric standard model thus includes all the necessary ingredients to realize a fermion spectrum that is qualitatively similar to observation, with hierarchical masses and mixing. The minimal framework produces only a few quantitative discrepancies with observation, most notably the muon mass is too low. Furthermore, we discuss simple modifications which resolve this and also investigate the compatibility of our model with gauge and Yukawa coupling Unification.
A new phase from compression of carbon nanotubes with anisotropic Dirac fermions
Dong, Xiao; Hu, Meng; He, Julong; Tian, Yongjun; Wang, Hui-Tian
2015-01-01
Searching for novel functional carbon materials is an enduring topic of scientific investigations, due to its diversity of bonds, including sp-, sp2-, and sp3-hybridized bonds. Here we predict a new carbon allotrope, bct-C12 with the body-centered tetragonal I4/mcm symmetry, from the compression of carbon nanotubes. In particular, this structure behaviors as the Dirac fermions in the kz direction and the classic fermions in the kx and ky directions. This anisotropy originates from the interaction among zigzag chains, which is inherited from (n, n)-naotubes. PMID:26030232
A new phase from compression of carbon nanotubes with anisotropic Dirac fermions.
Dong, Xiao; Hu, Meng; He, Julong; Tian, Yongjun; Wang, Hui-Tian
2015-01-01
Searching for novel functional carbon materials is an enduring topic of scientific investigations, due to its diversity of bonds, including sp-, sp(2)-, and sp(3)-hybridized bonds. Here we predict a new carbon allotrope, bct-C12 with the body-centered tetragonal I4/mcm symmetry, from the compression of carbon nanotubes. In particular, this structure behaviors as the Dirac fermions in the kz direction and the classic fermions in the kx and ky directions. This anisotropy originates from the interaction among zigzag chains, which is inherited from (n, n)-naotubes. PMID:26030232
Resonances of Spin-1/2 Fermions in Eddington-Inspired Born-Infeld Gravity
NASA Astrophysics Data System (ADS)
Fu, Qi-Ming; Zhao, Li; Du, Yun-Zhi; Gu, Bao-Min
2016-03-01
We investigate the fermionic resonances for both chiralities in five-dimensional Eddington-inspired Born-Infeld (EiBI) theory. In order to localize fermion on the brane, it needs to be considered the Yukawa coupling between the fermion and the background scalar field. In our models, since the background scalar field has kink, double kink, or anti-kink solution, the system has rich resonant Kaluza–Klein (KK) modes structure. The massive KK fermionic modes feel a volcano potential, which result in a fermionic zero mode and a set of continuous massive KK modes. The inner structure of the branes and a free parameter in background scalar field influence the resonant behaviors of the massive KK fermions. Supported in part by the National Natural Science Foundation of China under Grant No. 11075065, the Huo Ying-Dong Education Foundation of Chinese Ministry of Education under Grant No. 121106 and the Fundamental Research Funds for the Central Universities under Grant No. lzujbky-2014-31
Cooling a Band Insulator with a Metal: Fermionic Superfluid in a Dimerized Holographic Lattice
NASA Astrophysics Data System (ADS)
Haldar, Arijit; Shenoy, Vijay B.
A cold atomic realization of a quantum correlated state of many fermions on a lattice, eg. superfluid, has eluded experimental realization due to the entropy problem. Here we propose a route to realize such a state using holographic lattice and confining potentials. The potentials are designed to produces a band insulating state (low heat capacity) at the trap center, and a metallic state (high heat capacity) at the periphery. The metal ``cools'' the central band insulator by extracting out the excess entropy. The central band insulator can be turned into a superfluid by tuning an attractive interaction between the fermions. Crucially, the holographic lattice allows the emergent superfluid to have a high transition temperature - even twice that of the effective trap temperature. The scheme provides a promising route to a laboratory realization of a fermionic lattice superfluid, even while being adaptable to simulate other many body states. Reference: Scientific Reports 4, 6665 (2014). Work supported by CSIR, DST and DAE.
Fermion tunneling from dynamical horizons
NASA Astrophysics Data System (ADS)
Di Criscienzo, R.; Vanzo, L.
2008-06-01
The instability against emission of fermionic particles by the trapping horizon of an evolving black hole is analyzed and confirmed using the Hamilton-Jacobi tunneling method. This method automatically selects one special expression for the surface gravity of a changing horizon. The results also apply to point masses embedded in an expanding universe. As a bonus of the tunneling method, we gain the insight that the surface gravity still defines a temperature parameter as long as the evolution is sufficiently slow that the black-hole pass through a sequence of quasi-equilibrium states, and that black holes should be semi-classically unstable even in a hypothetical world without bosonic fields.
Green's functions for a CPn - 1 model with massless fermions
NASA Astrophysics Data System (ADS)
Schaposnik, F. A.
1983-07-01
We study the CPn - 1 model with massless fermions making a chiral change in the fermionic variables. We construct the generating functional and discuss relevant features of the theory. The factorization of a pure fermionic part shows a power law correction to the free fermion Green's function. The dynamical gauge field becomes massive and a screening phenomenon occurs. Member of CIC, Buenos Aires, Argentina
Flavor symmetries and fermion masses
Rasin, A.
1994-04-01
We introduce several ways in which approximate flavor symmetries act on fermions and which are consistent with observed fermion masses and mixings. Flavor changing interactions mediated by new scalars appear as a consequence of approximate flavor symmetries. We discuss the experimental limits on masses of the new scalars, and show that the masses can easily be of the order of weak scale. Some implications for neutrino physics are also discussed. Such flavor changing interactions would easily erase any primordial baryon asymmetry. We show that this situation can be saved by simply adding a new charged particle with its own asymmetry. The neutrality of the Universe, together with sphaleron processes, then ensures a survival of baryon asymmetry. Several topics on flavor structure of the supersymmetric grand unified theories are discussed. First, we show that the successful predictions for the Kobayashi-Maskawa mixing matrix elements, V{sub ub}/V{sub cb} = {radical}m{sub u}/m{sub c} and V{sub td}/V{sub ts} = {radical}m{sub d}/m{sub s}, are a consequence of a large class of models, rather than specific properties of a few models. Second, we discuss how the recent observation of the decay {beta} {yields} s{gamma} constrains the parameter space when the ratio of the vacuum expectation values of the two Higgs doublets, tan{Beta}, is large. Finally, we discuss the flavor structure of proton decay. We observe a surprising enhancement of the branching ratio for the muon mode in SO(10) models compared to the same mode in the SU(5) model.
Fitting fermion masses and mixings in F-theory GUTs
NASA Astrophysics Data System (ADS)
Carta, Federico; Marchesano, Fernando; Zoccarato, Gianluca
2016-03-01
We analyse the structure of Yukawa couplings in local SU(5) F-theory models with E 7 enhancement. These models are the minimal setting in which the whole flavour structure for the MSSM charged fermions is encoded in a small region of the entire compactification space. In this setup the E 7 symmetry is broken down to SU(5) by means of a 7-brane T-brane background, and further to the MSSM gauge group by means of a hypercharge flux that also implements doublet-triplet splitting. At tree-level only one family of quarks and charged leptons is massive, while the other two obtain hierarchically smaller masses when stringy non-perturbative effects are taken into account. We find that there is a unique E 7 model with such hierarchical flavour structure. The relative simplicity of the model allows to perform the computation of Yukawa couplings for a region of its parameter space wider than previous attempts, obtaining realistic fermion masses and mixings for large parameter regions. Our results are also valid for local models with E 8 enhancement, pointing towards a universal structure to describe realistic fermion masses within this framework.
Zimbardi, Kirsten; Bugarcic, Andrea; Colthorpe, Kay; Good, Jonathan P; Lluka, Lesley J
2013-12-01
Science graduates require critical thinking skills to deal with the complex problems they will face in their 21st century workplaces. Inquiry-based curricula can provide students with the opportunities to develop such critical thinking skills; however, evidence suggests that an inappropriate level of autonomy provided to underprepared students may not only be daunting to students but also detrimental to their learning. After a major review of the Bachelor of Science, we developed, implemented, and evaluated a series of three vertically integrated courses with inquiry-style laboratory practicals for early-stage undergraduate students in biomedical science. These practical curricula were designed so that students would work with increasing autonomy and ownership of their research projects to develop increasingly advanced scientific thinking and communication skills. Students undertaking the first iteration of these three vertically integrated courses reported learning gains in course content as well as skills in scientific writing, hypothesis construction, experimental design, data analysis, and interpreting results. Students also demonstrated increasing skills in both hypothesis formulation and communication of findings as a result of participating in the inquiry-based curricula and completing the associated practical assessment tasks. Here, we report the specific aspects of the curricula that students reported as having the greatest impact on their learning and the particular elements of hypothesis formulation and communication of findings that were more challenging for students to master. These findings provide important implications for science educators concerned with designing curricula to promote scientific thinking and communication skills alongside content acquisition. PMID:24292906
Instantons and Massless Fermions in Two Dimensions
DOE R&D Accomplishments Database
Callan, C. G. Jr.; Dashen, R.; Gross, D. J.
1977-05-01
The role of instantons in the breakdown of chiral U(N) symmetry is studied in a two dimensional model. Chiral U(1) is always destroyed by the axial vector anomaly. For N = 2 chiral SU(N) is also spontaneously broken yielding massive fermions and three (decoupled) Goldstone bosons. For N greater than or equal to 3 the fermions remain massless. Realistic four dimensional theories are believed to behave in a similar way but the critical N above which the fermions cease to be massive is not known in four dimensions.
Fermion localization on a split brane
Chumbes, A. E. R.; Vasquez, A. E. O.; Hott, M. B.
2011-05-15
In this work we analyze the localization of fermions on a brane embedded in five-dimensional, warped and nonwarped, space-time. In both cases we use the same nonlinear theoretical model with a nonpolynomial potential featuring a self-interacting scalar field whose minimum energy solution is a soliton (a kink) which can be continuously deformed into a two-kink. Thus a single brane splits into two branes. The behavior of spin 1/2 fermions wave functions on the split brane depends on the coupling of fermions to the scalar field and on the geometry of the space-time.
Fermionic quantum critical point of spinless fermions on a honeycomb lattice
NASA Astrophysics Data System (ADS)
Wang, Lei; Corboz, Philippe; Troyer, Matthias
2014-10-01
Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of the Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recent discovery (Huffman and Chandrasekharan 2014 Phys. Rev. B 89 111101) of the absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous-time quantum Monte Carlo method with a worm-sampling technique. We estimate the transition point V/t=1.356(1) with the critical exponents ν =0.80(3) and η =0.302(7). Compatible results for the transition point are also obtained with infinite projected entangled-pair states.
Pfaffian wave functions and topology of fermion nodes
NASA Astrophysics Data System (ADS)
Mitas, Lubos
2007-03-01
Pfaffian is defined as a signed sum of all pair partitions of even number of elements and it can be viewed as a nontrivial generalization of determinant. Pfaffian enables to define the simplest possible antisymmetric wave function based on pair spinorbital(s) and therefore represents a pairing generalization of the Slater determinant of one-particle orbitals. Pfaffians actually accomodate several types of pairing wave functions, for example, one special case is the Bardeen-Cooper- Schrieffer wave function. Using this platform we propose pfaffian wave functions with simultaneous pairings both in singlet and triplet channels and we benchmark their performance in fixed-node quantum Monte Carlo. We implement Gaussian elimination-like algorithm which enables to calculate pfaffians with efficiency similar to calculation of determinants. For a testing set of first row atoms and molecules we show that single pfaffians provide correlation energies systematically at the level of about 95%. Linear combinations of small number of pfaffians recover another fraction of the missing correlation energy comparable to significantly larger determinantal expansions. In addition, we show that pfaffians possess an important property of fermionic wave functions, namely, the minimal number of two nodal domains defined by fermion nodes. This is related to the proof that under rather general conditions closed-shell ground state wave functions of fermionic systems in d>1 have two nodal domains for arbitrary system size. The explicit proofs cover a number of paradigmatic models such as fermions on a sphere surface, in a periodic box, atomic states, etc, and we discuss the implications of this on efficient construction of wave functions and on several types of many-body effects. Supported by NSF and done in collaboration with M. Bajdich, L.K. Wagner, G. Drobny, and K.E Schmidt.Refs: L. Mitas, PRL 96, 240402 (2006); L. Mitas, cond-mat/0605550; M. Bajdich et al, PRL 96, 130201 (2006); cond
Kizilersue, Ayse; Pennington, Michael R.
2009-06-15
In principle, calculation of a full Green's function in any field theory requires knowledge of the infinite set of multipoint Green's functions, unless one can find some way of truncating the corresponding Schwinger-Dyson equations. For the fermion and boson propagators in QED this requires an ansatz for the full 3-point vertex. Here we illustrate how the properties of gauge invariance, gauge covariance and multiplicative renormalizability impose severe constraints on this fermion-boson interaction, allowing a consistent truncation of the propagator equations. We demonstrate how these conditions imply that the 3-point vertex in the propagator equations is largely determined by the behavior of the fermion propagator itself and not by knowledge of the many higher-point functions. We give an explicit form for the fermion-photon vertex, which in the fermion and photon propagator fulfills these constraints to all orders in leading logarithms for massless QED, and accords with the weak coupling limit in perturbation theory at O({alpha}). This provides the first attempt to deduce nonperturbative Feynman rules for strong physics calculations of propagators in massless QED that ensure a more consistent truncation of the 2-point Schwinger-Dyson equations. The generalization to next-to-leading order and masses will be described in a longer publication.
Quantum-gas microscope for fermionic atoms.
Cheuk, Lawrence W; Nichols, Matthew A; Okan, Melih; Gersdorf, Thomas; Ramasesh, Vinay V; Bakr, Waseem S; Lompe, Thomas; Zwierlein, Martin W
2015-05-15
We realize a quantum-gas microscope for fermionic ^{40}K atoms trapped in an optical lattice, which allows one to probe strongly correlated fermions at the single-atom level. We combine 3D Raman sideband cooling with high-resolution optics to simultaneously cool and image individual atoms with single-lattice-site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site-resolved imaging of fermions enables the direct observation of magnetic order, time-resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement. PMID:26024169
Chiral fermions in asymptotically safe quantum gravity
NASA Astrophysics Data System (ADS)
Meibohm, J.; Pawlowski, J. M.
2016-05-01
We study the consistency of dynamical fermionic matter with the asymptotic safety scenario of quantum gravity using the functional renormalisation group. Since this scenario suggests strongly coupled quantum gravity in the UV, one expects gravity-induced fermion self-interactions at energies of the Planck scale. These could lead to chiral symmetry breaking at very high energies and thus to large fermion masses in the IR. The present analysis which is based on the previous works (Christiansen et al., Phys Rev D 92:121501, 2015; Meibohm et al., Phys Rev D 93:084035, 2016), concludes that gravity-induced chiral symmetry breaking at the Planck scale is avoided for a general class of NJL-type models. We find strong evidence that this feature is independent of the number of fermion fields. This finding suggests that the phase diagram for these models is topologically stable under the influence of gravitational interactions.
Lifetime of a one-dimensional fermion
NASA Astrophysics Data System (ADS)
Khodas, Maxim; Ussishkin, Iddo; Pustilnik, Michael; Kamenev, Alex; Glazman, Leonid
2007-03-01
Interaction between fermions in one dimension is usually accounted for within the exactly solvable Tomonaga-Luttinger model. The crucial simplification made in this model is the linearization of the fermionic spectrum. That simplification leads to an infinite lifetime of a fermion at the mass shell, i.e., the corresponding Green function G(,k) diverges at ɛ=ξk. We find that inclusion of the curvature of electron spectrum, ξk=vFk+k^2/2m, yields a finite decay rate of a fermion, 1/τ(ξk)θ(k)k^8/m^3; here for definiteness we consider right-moving particles, and k is measured from the Fermi wave vector. The found finite lifetime allows one to assess the limitations of the Luttinger liquid paradigm.
Quantum Materials: Weyl fermions go into orbit
NASA Astrophysics Data System (ADS)
Dai, Xi
2016-08-01
Due to their chirality, the massless fermions inside Weyl semimetals can take unusual paths that are governed by chiral dynamics, potentially providing a direct method to explore their topological nature.
Majorana Fermions and Topology in Superconductors
NASA Astrophysics Data System (ADS)
Sato, Masatoshi; Fujimoto, Satoshi
2016-07-01
Topological superconductors are novel classes of quantum condensed phases, characterized by topologically nontrivial structures of Cooper pairing states. On the surfaces of samples and in vortex cores of topological superconductors, Majorana fermions, which are particles identified with their own anti-particles, appear as Bogoliubov quasiparticles. The existence and stability of Majorana fermions are ensured by bulk topological invariants constrained by the symmetries of the systems. Majorana fermions in topological superconductors obey a new type of quantum statistics referred to as non-Abelian statistics, which is distinct from bose and fermi statistics, and can be utilized for application to topological quantum computation. Also, Majorana fermions give rise to various exotic phenomena such as "fractionalization", non-local correlation, and "teleportation". A pedagogical review of these subjects is presented. We also discuss interaction effects on topological classification of superconductors, and the basic properties of Weyl superconductors.
Quantum-Gas Microscope for Fermionic Atoms
NASA Astrophysics Data System (ADS)
Cheuk, Lawrence W.; Nichols, Matthew A.; Okan, Melih; Gersdorf, Thomas; Ramasesh, Vinay V.; Bakr, Waseem S.; Lompe, Thomas; Zwierlein, Martin W.
2015-05-01
We realize a quantum-gas microscope for fermionic 40K atoms trapped in an optical lattice, which allows one to probe strongly correlated fermions at the single-atom level. We combine 3D Raman sideband cooling with high-resolution optics to simultaneously cool and image individual atoms with single-lattice-site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site-resolved imaging of fermions enables the direct observation of magnetic order, time-resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement.
Ground state degeneracy of interacting spinless fermions
NASA Astrophysics Data System (ADS)
Wei, Zhong-Chao; Han, Xing-Jie; Xie, Zhi-Yuan; Xiang, Tao
2015-10-01
We propose an eigenoperator scheme to study the lattice model of interacting spinless fermions at half filling and show that this model possesses a hidden form of reflection positivity in its Majorana fermion representation. Based on this observation, we prove rigourously that the ground state of this model is either unique or doubly degenerate if the lattice size N is even, and is always doubly degenerate if N is odd. This proof holds in all dimensions with arbitrary lattice structures.
Creutz fermions on an orthogonal lattice
Borici, Artan
2008-10-01
In a recent paper, Creutz has given a new action describing two species of Dirac fermions with exact chiral symmetry on the lattice. This action depends on parameters which may be fixed at certain values in order to get the right continuum limit. In this letter, we elaborate more on this idea and present an action which is free of any other parameter except the fermion mass.
Dual of QCD with one adjoint fermion
Mojaza, Matin; Nardecchia, Marco; Pica, Claudio; Sannino, Francesco
2011-03-15
We construct the magnetic dual of QCD with one adjoint Weyl fermion. The dual is a consistent solution of the 't Hooft anomaly matching conditions, allows for flavor decoupling, and remarkably constitutes the first nonsupersymmetric dual valid for any number of colors. The dual allows to bound the anomalous dimension of the Dirac fermion mass operator to be less than one in the conformal window.
The physics and chemistry of heavy fermions.
Fisk, Z; Sarrao, J L; Smith, J L; Thompson, J D
1995-01-01
The heavy fermions are a subset of the f-electron intermetallic compounds straddling the magnetic/nonmagnetic boundary. Their low-temperature properties are characterized by an electronic energy scale of order 1-10 K. Among the low-temperature ground states observed in heavy fermion compounds are exotic superconductors and magnets, as well as unusual semiconductors. We review here the current experimental and theoretical understanding of these systems. PMID:11607558
Fermionic Subspaces of the Bosonic String
NASA Astrophysics Data System (ADS)
Chattaraputi, A.; Englert, F.; Houart, L.; Taormina, A.
A universal symmetric truncation of the bosonic string Hilbert space yields all known closed fermionic string theories in ten dimensions, their D-branes and their open descendants. We highlight the crucial role played by group theory and two-dimensional conformal field theory in the construction and emphasize the predictive power of the truncation. Such circumstantial evidence points towards the existence of a mechanism which generates space-time fermions out of bosons dynamically within the framework of bosonic string theory.
Fermionic subspaces of the bosonic string
NASA Astrophysics Data System (ADS)
Chattaraputi, Auttakit; Englert, François; Houart, Laurent; Taormina, Anne
2003-06-01
A universal symmetric truncation of the bosonic string Hilbert space yields all known closed fermionic string theories in ten dimensions, their D-branes and their open descendants. We highlight the crucial role played by group theory and two-dimensional conformal field theory in the construction and emphasize the predictive power of the truncation. Such circumstantial evidence points towards the existence of a mechanism which generates spacetime fermions out of bosons dynamically within the framework of bosonic string theory.
Quantum Gas Microscope for Fermionic Atoms
NASA Astrophysics Data System (ADS)
Okan, Melih; Cheuk, Lawrence; Nichols, Matthew; Lawrence, Katherine; Zhang, Hao; Zwierlein, Martin
2016-05-01
Strongly interacting fermions define the properties of complex matter throughout nature, from atomic nuclei and modern solid state materials to neutron stars. Ultracold atomic Fermi gases have emerged as a pristine platform for the study of many-fermion systems. In this poster we demonstrate the realization of a quantum gas microscope for fermionic 40 K atoms trapped in an optical lattice and the recent experiments which allows one to probe strongly correlated fermions at the single atom level. We combine 3D Raman sideband cooling with high- resolution optics to simultaneously cool and image individual atoms with single lattice site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site resolved imaging of fermions enables the direct observation of magnetic order, time resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement. NSF, AFOSR-PECASE, AFOSR-MURI on Exotic Phases of Matter, ARO-MURI on Atomtronics, ONR, a Grant from the Army Research Office with funding from the DARPA OLE program, and the David and Lucile Packard Foundation.
Iterants, Fermions and Majorana Operators
NASA Astrophysics Data System (ADS)
Kauffman, Louis H.
Beginning with an elementary, oscillatory discrete dynamical system associated with the square root of minus one, we study both the foundations of mathematics and physics. Position and momentum do not commute in our discrete physics. Their commutator is related to the diffusion constant for a Brownian process and to the Heisenberg commutator in quantum mechanics. We take John Wheeler's idea of It from Bit as an essential clue and we rework the structure of that bit to a logical particle that is its own anti-particle, a logical Marjorana particle. This is our key example of the amphibian nature of mathematics and the external world. We show how the dynamical system for the square root of minus one is essentially the dynamics of a distinction whose self-reference leads to both the fusion algebra and the operator algebra for the Majorana Fermion. In the course of this, we develop an iterant algebra that supports all of matrix algebra and we end the essay with a discussion of the Dirac equation based on these principles.
Fermionic pentagons and NMHV hexagon
NASA Astrophysics Data System (ADS)
Belitsky, A. V.
2015-05-01
We analyze the near-collinear limit of the null polygonal hexagon super Wilson loop in the planar N = 4 super-Yang-Mills theory. We focus on its Grassmann components which are dual to next-to-maximal helicity-violating (NMHV) scattering amplitudes. The kinematics in question is studied within a framework of the operator product expansion that encodes propagation of excitations on the background of the color flux tube stretched between the sides of Wilson loop contour. While their dispersion relation is known to all orders in 't Hooft coupling from previous studies, we find their form factor couplings to the Wilson loop. This is done making use of a particular tessellation of the loop where pentagon transitions play a fundamental role. Being interested in NMHV amplitudes, the corresponding building blocks carry a nontrivial charge under the SU(4) R-symmetry group. Restricting the current consideration to twist-two accuracy, we analyze two-particle contributions with a fermion as one of the constituents in the pair. We demonstrate that these nonsinglet pentagons obey bootstrap equations that possess consistent solutions for any value of the coupling constant. To confirm the correctness of these predictions, we calculate their contribution to the super Wilson loop demonstrating agreement with recent results to four-loop order in 't Hooft coupling.
Heavy fermion behavior explained by bosons
NASA Technical Reports Server (NTRS)
Kallio, A.; Poykko, S.; Apaja, V.
1995-01-01
Conventional heavy fermion (HF) theories require existence of massive fermions. We show that heavy fermion phenomena can also be simply explained by existence of bosons with moderate mass but temperature dependent concentration below the formation temperature T(sub B), which in turn is close to room temperature. The bosons B(++) are proposed to be in chemical equilibrium with a system of holes h(+): B(++) = h(+) + h(+). This equilibrium is governed by a boson breaking function f(T), which determines the decreasing boson density and the increasing fermion density with increasing temperature. Since HF-compounds are hybridized from minimum two elements, we assume in addition existence of another fermion component h(sub s)(+) with temperature independent density. This spectator component is thought to be the main agent in binding the bosons in analogy with electronic or muonic molecules. Using a linear boson breaking function we can explain temperature dependence of the giant linear specific heat coefficient gamma(T) coming essentially from bosons. The maxima in resistivity, Hall coefficient, and susceptibility are explained by boson localization effects due to the Wigner crystallization. The antiferromagnetic transitions in turn are explained by similar localization of the pairing fermion system when their density n(sub h)(T(sub FL)) becomes lower than n(sub WC), the critical density of Wigner crystallization. The model applies irrespective whether a compound is superconducting or not. The same model explains the occurrence of low temperature antiferromagnetism also in high-T(sub c) superconductors. The double transition in UPt3 is proposed to be due to the transition of the pairing fermion liquid from spin polarized to unpolarized state.
Fermionic entanglement that survives a black hole
Martin-Martinez, Eduardo; Leon, Juan
2009-10-15
We introduce an arbitrary number of accessible modes when analyzing bipartite entanglement degradation due to Unruh effect between two partners Alice and Rob. Under the single mode approximation (SMA) a fermion field only had a few accessible levels due to Pauli exclusion principle conversely to bosonic fields which had an infinite number of excitable levels. This was argued to justify entanglement survival in the fermionic case in the SMA infinite acceleration limit. Here we relax SMA. Hence, an infinite number of modes are excited as the observer Rob accelerates, even for a fermion field. We will prove that, despite this analogy with the bosonic case, entanglement loss is limited. We will show that this comes from fermionic statistics through the characteristic structure it imposes on the infinite dimensional density matrix for Rob. Surprisingly, the surviving entanglement is independent of the specific maximally entangled state chosen, the kind of fermionic field analyzed, and the number of accessible modes considered. We shall discuss whether this surviving entanglement goes beyond the purely statistical correlations, giving insight concerning the black hole information paradox.
Instabilities in fermions and BEC mixtures
NASA Astrophysics Data System (ADS)
Tsai, Shan-Wen; Kalas, Ryan M.; Timmermans, Eddy
2010-03-01
We study instabilities in a mixture of interacting fermionic and bosonic ultra-cold atoms. We focus on BCS transitions of the fermions that can be generated from attractive interactions mediated by bosons that are in a BEC phase. We study the p-wave instability [1] for indistinguishable (single spin) fermions in detail, taking into account the dynamical part of the mediated interaction. We employ a functional renormalization-group approach that takes retardation effects into account [2], calculate the renormalized interaction vertices and self-energies for this system, and obtain the phase diagram, sub-dominant instabilities, and transition temperatures, giving estimates for realistic parameters. We also investigate what happens in this system close to the phase-separation transition [3], and explore other possible fermionic phases, including fermion BCS pairings with other pairing symmetries. [4pt] [1] D. V. Efremov and L. Viverit, Phys. Rev. B 65, 134519 (2002)[0pt] [2] S.-W. Tsai et al., Phys. Rev. B 72, 054531 (2005)[0pt] [3] D. H. Santamore and E. Timmermans, Phys. Rev. A 78, 013619 (2008)
Fermionic entanglement that survives a black hole
NASA Astrophysics Data System (ADS)
Martín-Martínez, Eduardo; León, Juan
2009-10-01
We introduce an arbitrary number of accessible modes when analyzing bipartite entanglement degradation due to Unruh effect between two partners Alice and Rob. Under the single mode approximation (SMA) a fermion field only had a few accessible levels due to Pauli exclusion principle conversely to bosonic fields which had an infinite number of excitable levels. This was argued to justify entanglement survival in the fermionic case in the SMA infinite acceleration limit. Here we relax SMA. Hence, an infinite number of modes are excited as the observer Rob accelerates, even for a fermion field. We will prove that, despite this analogy with the bosonic case, entanglement loss is limited. We will show that this comes from fermionic statistics through the characteristic structure it imposes on the infinite dimensional density matrix for Rob. Surprisingly, the surviving entanglement is independent of the specific maximally entangled state chosen, the kind of fermionic field analyzed, and the number of accessible modes considered. We shall discuss whether this surviving entanglement goes beyond the purely statistical correlations, giving insight concerning the black hole information paradox.
Contraction of fermionic operator circuits and the simulation of strongly correlated fermions
NASA Astrophysics Data System (ADS)
Barthel, Thomas; Pineda, Carlos; Eisert, Jens
2009-10-01
A fermionic operator circuit is a product of fermionic operators of usually different and partially overlapping support. Further elements of fermionic operator circuits (FOCs) are partial traces and partial projections. The presented framework allows for the introduction of fermionic versions of known qudit operator circuits (QUOC), important for the simulation of strongly correlated d -dimensional systems: the multiscale entanglement renormalization ansätze (MERA), tree tensor networks (TTN), projected entangled pair states (PEPS), or their infinite-size versions (iPEPS etc.). After the definition of a FOC, we present a method to contract it with the same computation and memory requirements as a corresponding QUOC, for which all fermionic operators are replaced by qudit operators of identical dimension. A given scheme for contracting the QUOC relates to an analogous scheme for the corresponding fermionic circuit, where additional marginal computational costs arise only from reordering of modes for operators occurring in intermediate stages of the contraction. Our result hence generalizes efficient schemes for the simulation of d -dimensional spin systems, as MERA, TTN, or PEPS to the fermionic case.
QCD with many fermions and QCD topology
NASA Astrophysics Data System (ADS)
Shuryak, Edward
2013-04-01
Major nonperturbative phenomena in QCD - confinement and chiral symmetry breaking - are known to be related with certain topological objects. Recent lattice advances into the domain of many Nf = O(10) fermion flavors have shown that both phase transitions had shifted in this case to much stronger coupling. We discuss confinement in terms of monopole Bose condensation, and discuss how it is affected by fermions "riding" on the monopoles, ending with the Nf dependence of the critical line. Chiral symmetry breaking is discussed in terms of the (anti)selfdual dyons, the instanton constituents. The fermionic zero modes of those have a different meaning and lead to strong interaction between dyons and antidyons. We report some qualitative consequences of this theory and also some information about our first direct numerical study of the dyonic ensemble, in respect to both chiral symmetry breaking and confinement (via back reaction to the holonomy potential).
Fermionic semi-annihilating dark matter
NASA Astrophysics Data System (ADS)
Cai, Yi; Spray, Andrew
2016-01-01
Semi-annihilation is a generic feature of dark matter theories with symmetries larger than Z_2 . We investigate two examples with multi-component dark sectors comprised of an SU(2) L singlet or triplet fermion besides a scalar singlet. These are respectively the minimal fermionic semi-annihilating model, and the minimal case for a gauge-charged fermion. We study the relevant dark matter phenomenology, including the interplay of semi-annihilation and the Sommerfeld effect. We demonstrate that semi-annihilation in the singlet model can explain the gamma ray excess from the galactic center. For the triplet model we scan the parameter space, and explore how signals and constraints are modified by semi-annihilation. We find that the entire region where the model comprises all the observed dark matter is accessible to current and planned direct and indirect searches.
Fermions on one or fewer kinks
Chu Yizen; Vachaspati, Tanmay
2008-01-15
We find the full spectrum of fermion bound states on a Z{sub 2} kink. In addition to the zero mode, there are int[2m{sub f}/m{sub s}] bound states, where m{sub f} is the fermion and m{sub s} the scalar mass. We also study fermion modes on the background of a well-separated kink-antikink pair. Using a variational argument, we prove that there is at least one bound state in this background, and that the energy of this bound state goes to zero with increasing kink-antikink separation, 2L, and faster than e{sup -a2L} where a=min(m{sub s},2m{sub f}). By numerical evaluation, we find some of the low lying bound states explicitly.
Plutonium-Based Heavy-Fermion Systems
NASA Astrophysics Data System (ADS)
Bauer, E. D.; Thompson, J. D.
2015-03-01
An effective mass of charge carriers that is significantly larger than the mass of a free electron develops at low temperatures in certain lanthanide- and actinide-based metals, including those formed with plutonium, owing to strong electron-electron interactions. This heavy-fermion mass is reflected in a substantially enhanced electronic coefficient of specific heat Î³, which for elemental Pu is much larger than that of normal metals. By our definition, there are twelve Pu-based heavy-fermion compounds, most discovered recently, whose basic properties are known and discussed. Relative to other examples, these Pu-based heavy-fermion systems are particularly complex owing in part to the possible simultaneous presence of multiple, nearly degenerate 5fn configurations. This complexity poses significant opportunities as well as challenges, including understanding the origin of unconventional superconductivity in some of these materials.
Apparatus for Ultra-Cold Fermion Interferometry
NASA Astrophysics Data System (ADS)
Aubin, Seth; Garcia, Aiyana; Desalvo, Brian
2008-05-01
We present progress on the construction of an apparatus for ultra-cold fermion interferometry experiments. The apparatus consists of two connected glass vacuum cells: Fermionic potassium (^40K) and bosonic rubidium (^87Rb) atoms are cooled and collected in a dual-species magneto-optical trap (MOT) in the first cell and are then transported magnetically to the second cell, where they are loaded into a micro-magnetic chip trap. We use radio-frequency (RF) evaporation to cool the rubidium atoms, which in turn sympathetically cool the potassium atoms. The apparatus takes advantage of the rapid cooling inherent to micro-magnetic traps, while also benefiting from the ultra high vacuum achievable with a two chamber vacuum system. In describing our experimental approach, we address the experimental challenges and possible force-sensing applications of fermion interferometers on chips.
Search for Majorana Fermions in Superconductors
NASA Astrophysics Data System (ADS)
Beenakker, C. W. J.
2013-04-01
Majorana fermions (particles that are their own antiparticle) may or may not exist in nature as elementary building blocks, but in condensed matter they can be constructed out of electron and hole excitations. What is needed is a superconductor to hide the charge difference and a topological (Berry) phase to eliminate the energy difference from zero-point motion. A pair of widely separated Majorana fermions, bound to magnetic or electrostatic defects, has non-Abelian exchange statistics. A qubit encoded in this Majorana pair is expected to have an unusually long coherence time. I discuss strategies to detect Majorana fermions in a topological superconductor, as well as possible applications in a quantum computer. The status of the experimental search is reviewed.
Dark Energy from Interacting Dark Fermions
NASA Astrophysics Data System (ADS)
Goldman, Terrence; McKellar, Bruce; Alsing, Paul; Stephenson, Gerard
2010-11-01
Physics is rife with interacting systems that exhibit negative pressure: atomic nuclei are very well known examples. We examine the range of parameters, for neutral fermions interacting only by exchange of an extraordinarily light scalar particle, that produce a negative pressure on the scale of the Universe over time periods where Dark Energy is or may be relevant. Of known or expected neutral Majorana fermions, active neutrinos can be ruled out but sterile neutrinos would work, as well as the LSP, to describe the recent observations of Dark Energy effects. After a phase change required by the instability responsible for the negative pressure, the resulting clouds of neutral fermions will contribute to Dark Matter. Nothing requires that this can only happen once.
Fermion boson metamorphosis in field theory
Ha, Y.K.
1982-01-01
In two-dimensional field theories many features are especially transparent if the Fermi fields are represented by non-local expressions of the Bose fields. Such a procedure is known as boson representation. Bilinear quantities appear in the Lagrangian of a fermion theory transform, however, as simple local expressions of the bosons so that the resulting theory may be written as a theory of bosons. Conversely, a theory of bosons may be transformed into an equivalent theory of fermions. Together they provide a basis for generating many interesting equivalences between theories of different types. In the present work a consistent scheme for constructing a canonical Fermi field in terms of a real scalar field is developed and such a procedure is valid and consistent with the tenets of quantum field theory is verified. A boson formulation offers a unifying theme in understanding the structure of many theories. This is illustrated by the boson formulation of a multifermion theory with chiral and internal symmetries. The nature of dynamical generation of mass when the theory undergoes boson transmutation and the preservation of continuous chiral symmetry in the massive case are examined. The dynamics of the system depends to a great extent on the specific number of fermions and different models of the same system can have very different properties. Many unusual symmetries of the fermion theory, such as hidden symmetry, duality and triality symmetries, are only manifest in the boson formulation. The underlying connections between some models with U(N) internal symmetry and another class of fermion models built with Majorana fermions which have O(2N) internal symmetry are uncovered.
Coffman-Kundu-Wootters inequality for fermions
NASA Astrophysics Data System (ADS)
Sárosi, Gábor; Lévay, Péter
2014-11-01
We derive an inequality for three fermions with six single-particle states which reduces to the sum of the famous Coffman-Kundu-Wootters inequalities when an embedded three-qubit system is considered. We identify the quantities which are playing the role of the concurrence, the three-tangle and the invariant detρA+detρB+detρC for this tripartite system. We show that this latter one is almost interchangeable with the von Neumann entropy and conjecture that it measures the entanglement of one fermion with the rest of the system. We prove that the vanishing of the fermionic "concurrence" implies that the two-particle reduced-density matrix is a mixture of separable states. Also, the vanishing of this quantity is only possible in the Greenberger-Horne-Zeilinger class, where some genuine tripartite entanglement is present and in the separable class. Based on this, we conjecture that this "concurrence" measures the amount of entanglement between pairs of fermions. We identify the well-known "spin-flipped" density matrix in the fermionic context as the reduced-density matrix of a special particle-hole dual state. We show that, in general, this dual state is always canonically defined by the Hermitian inner product of the fermionic Fock space and that it can be used to calculate covariants under stochastic local operations and classical communication (SLOCC). We show that Fierz identities known from the theory of spinors relate SLOCC covariants with reduced-density-matrix elements of the state and its spin-flipped dual.
Fermion-fermion scattering in quantum field theory with superconducting circuits.
García-Álvarez, L; Casanova, J; Mezzacapo, A; Egusquiza, I L; Lamata, L; Romero, G; Solano, E
2015-02-20
We propose an analog-digital quantum simulation of fermion-fermion scattering mediated by a continuum of bosonic modes within a circuit quantum electrodynamics scenario. This quantum technology naturally provides strong coupling of superconducting qubits with a continuum of electromagnetic modes in an open transmission line. In this way, we propose qubits to efficiently simulate fermionic modes via digital techniques, while we consider the continuum complexity of an open transmission line to simulate the continuum complexity of bosonic modes in quantum field theories. Therefore, we believe that the complexity-simulating-complexity concept should become a leading paradigm in any effort towards scalable quantum simulations. PMID:25763944
Scaling of fat-link irrelevant-clover fermions
Zanotti, J.M.; Lasscock, B.; Leinweber, D.B.; Williams, A.G.
2005-02-01
Hadron masses are calculated in quenched lattice QCD on a variety of lattices in order to probe the scaling behavior of the Fat-Link Irrelevant Clover (FLIC) fermion action, a fat-link clover fermion action in which the purely irrelevant operators of the fermion action are constructed using APE-smeared links. The scaling analysis indicates FLIC fermions provide a new form of nonperturbative O(a) improvement where near-continuum results are obtained at finite lattice spacing.
Origin of fermion masses without spontaneous symmetry breaking
NASA Astrophysics Data System (ADS)
Ayyar, Venkitesh; Chandrasekharan, Shailesh
2016-04-01
Using large scale Monte Carlo calculations in a simple three dimensional lattice fermion model, we establish the existence of a second order quantum phase transition between a massless fermion phase and a massive one, both of which have the same symmetries. This shows that fermion masses can arise due to dynamics without the need for spontaneous symmetry breaking. Universality suggests that this alternate origin of the fermion mass should be of fundamental interest.
The bosonic mother of fermionic D-branes
NASA Astrophysics Data System (ADS)
Chattaraputi, Auttakit; Englert, François; Houart, Laurent; Taormina, Anne
2002-09-01
We extend the search for fermionic subspaces of the bosonic string compactified on E8 × SO(16) lattices to include all fermionic D-branes. This extension constraints the truncation procedure previously proposed and relates the fermionic strings, supersymmetric or not, to the global structure of the SO(16) group. The specific properties of all the fermionic D-branes are found to be encoded in its universal covering, whose maximal toroid defines the configuration space torus of their mother bosonic theory.
Resonant pairing between fermions with unequal masses
Wu, Shin-Tza; Pao, C.-H.; Yip, S.-K.
2006-12-01
We study via mean-field theory the pairing between fermions of different masses, especially at the unitary limit. At equal populations, the thermodynamic properties are identical with the equal mass case provided an appropriate rescaling is made. At unequal populations, for sufficiently light majority species, the system does not phase separate. For sufficiently heavy majority species, the phase separated normal phase have a density larger than that of the superfluid. For atoms in harmonic traps, the density profiles for unequal mass fermions can be drastically different from their equal-mass counterparts.
Fermion path integrals and topological phases
NASA Astrophysics Data System (ADS)
Witten, Edward
2016-07-01
Symmetry-protected topological (SPT) phases of matter have been interpreted in terms of anomalies, and it has been expected that a similar picture should hold for SPT phases with fermions. Here a description is given in detail of what this picture means for phases of quantum matter that can be understood via band theory and free fermions. The main examples considered are time-reversal invariant topological insulators and superconductors in two or three space dimensions. Along the way, the precise meaning of the statement that in the bulk of a 3D topological insulator, the electromagnetic θ angle is equal to π , is clarified.
Quark seesaw, vectorlike fermions and diphoton excess
NASA Astrophysics Data System (ADS)
Dev, P. S. Bhupal; Mohapatra, Rabindra N.; Zhang, Yongchao
2016-02-01
We present a possible interpretation of the recent diphoton excess reported by the early √{s}=13 TeV LHC data in quark seesaw left-right models with vectorlike fermions proposed to solve the strong CP problem without the axion. The gauge singlet real scalar field responsible for the mass of the vectorlike fermions has the right production cross section and diphoton branching ratio to be identifiable with the reported excess at around 750 GeV diphoton invariant mass. Various ways to test this hypothesis as more data accumulates at the LHC are proposed.
Condensation of gauge interacting massless fermions
Siringo, Fabio
2004-09-15
A single massless fermionic field with an Abelian U(1) gauge interaction (electrodynamics of a massless Dirac fermion) is studied by a variational method. Even without the insertion of any extra interaction the vacuum is shown to be unstable towards a particle-antiparticle condensate. The single particle excitations do acquire a mass and behave as massive Fermi particles. An explicit low-energy gap equation has been derived and numerically solved. Some consequences of condensation and mass generation are discussed in the framework of the standard model.
Massless rotating fermions inside a cylinder
Ambruş, Victor E.; Winstanley, Elizabeth
2015-12-07
We study rotating thermal states of a massless quantum fermion field inside a cylinder in Minkowski space-time. Two possible boundary conditions for the fermion field on the cylinder are considered: the spectral and MIT bag boundary conditions. If the radius of the cylinder is sufficiently small, rotating thermal expectation values are finite everywhere inside the cylinder. We also study the Casimir divergences on the boundary. The rotating thermal expectation values and the Casimir divergences have different properties depending on the boundary conditions applied at the cylinder. This is due to the local nature of the MIT bag boundary condition, while the spectral boundary condition is nonlocal.
Novel Fat-Link Fermion Actions
J. M. Zanotti; S. Bilson-Thompson; F. D. R. Bonnet; P. D. Coddington; D. B. Leinweber; A. G. Williams; J. B. Zhang; W. Melnitchouk; F. X. Lee
2001-07-01
The hadron mass spectrum is calculated in lattice QCD using a novel fat-link clover fermion action in which only the irrelevant operators in the fermion action are constructed using smeared links. The simulations are performed on a 16{sup 3} x 32 lattice with a lattice spacing of a=0.125 fm. We compare actions with n=4 and 12 smearing sweeps with a smearing fraction of 0.7. The n=4 Fat-Link Irrelevant Clover (FLIC) action provides scaling which is superior to mean-field improvement, and offers advantages over nonperturbative 0(a) improvement.
Global analysis of fermion mixing with exotics
NASA Technical Reports Server (NTRS)
Nardi, Enrico; Roulet, Esteban; Tommasini, Daniele
1991-01-01
The limits are analyzed on deviation of the lepton and quark weak-couplings from their standard model values in a general class of models where the known fermions are allowed to mix with new heavy particles with exotic SU(2) x U(1) quantum number assignments (left-handed singlets or right-handed doublets). These mixings appear in many extensions of the electroweak theory such as models with mirror fermions, E(sub 6) models, etc. The results update previous analyses and improve considerably the existing bounds.
Non-Markovian dynamics with fermions
NASA Astrophysics Data System (ADS)
Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Lacroix, D.
2014-08-01
Employing the quadratic fermionic Hamiltonians for the collective and internal subsystems with a linear coupling, we studied the role of fermionic statistics on the dynamics of the collective motion. The transport coefficients are discussed as well as the associated fluctuation-dissipation relation. Due to different nature of the particles, the path to equilibrium is slightly affected. However, in the weak-coupling regime, the time scale for approaching equilibrium is found to be globally unchanged. The Pauli-blocking effect can modify the usual picture in open quantum system. In some limits, contrary to boson, this effect can strongly hinder the influence of the bath by blocking the interacting channels.
Spontaneous polarization of composite fermions in the n = 1 Landau level of graphene
NASA Astrophysics Data System (ADS)
Coimbatore Balram, Ajit; Tőke, Csaba; Wójs, Arkadiusz; Jain, Jainendra
Motivated by experiments that reveal expansive fractional quantum Hall states in the n = 1 graphene Landau level and suggest a nontrivial role of the spin degree of freedom [Amet et al., Nat. Commun. 6, 5838 (2014)], we perform accurate quantitative study of the the competition between fractional quantum Hall states with different spin polarizations in the n = 1 graphene Landau level. We find that the fractional quantum Hall effect is well described in terms of composite fermions, but the spin physics is qualitatively different from that in the n = 0 Landau level. In particular, for the states at filling factors ν = s / (2 s +/- 1) , s integer, a combination of exact diagonalization and the composite fermion theory shows that the ground state is fully spin polarized and supports a robust spin wave mode even in the limit of vanishing Zeeman coupling. Thus, even though composite fermions are formed, a mean field description that treats them as weakly interacting particles breaks down, and the exchange interaction between them is strong enough to cause a qualitative change in the behavior by inducing full spin polarization. We also find that the fully spin polarized composite fermion Fermi sea has lower energy than the paired Pfaffian state at the relevant half fillings. Award No. DE-SC0005042 (ACB, JKJ), Hungarian Scientific Research Funds No. K105149 (CT), the Polish NCN Grant 2014/14/A/ST3/00654 and the EU Marie Curie Grant PCIG09-GA-2011-294186 (AW).
Zero-energy modes, charge conjugation, and fermion number
Sudarshan, E.C.G.; Yajnik, U.A.
1986-03-15
States with a half-integer fermion number occur when a fermionic field coupled to a soliton possesses a zero mode. This paper spells out the circumstances under which one can retain an integer fermion number as also a charge-conjugation-invariant ground state. It is necessary to make the representation reducible but it is kept irreducible by introducing an additional operator.
Fermionic computation is non-local tomographic and violates monogamy of entanglement
NASA Astrophysics Data System (ADS)
D'Ariano, G. M.; Manessi, F.; Perinotti, P.; Tosini, A.
2014-07-01
We show that the computational model based on local fermionic modes in place of qubits does not satisfy local tomography and monogamy of entanglement, and has mixed states with maximal entanglement of formation. These features directly follow from the parity superselection rule. We generalize quantum superselection rules to general probabilistic theories as sets of linear constraints on the convex set of states. We then provide a link between the cardinality of the superselection rule and the degree of holism of the resulting theory.
Fermion-fermion interaction in a dilute gas-mixture Bose condensate
Mogilyuk, T. I.
2011-11-15
A mixture of a one-component Bose gas and two-component Fermi gas is considered at temperatures at which the Bose gas is completely condensed. Two fermions in such a mixture can interact with each other exchanging bosons from the condensate or supercondensate. The interaction potential, a change in the effective mass, the decay, and fermion spectrum are calculated in this quantum Fermi-Bose mixture.
Fermions Living in a Flat World
Jesus Anguiano-Galicia, Ma. de; Bashir, A.
2006-09-25
In a plane, parity transformation, which changes the sign of only one spatial coordinate, swaps the fermion fields living in two inequivalent representations. A parity invariant Lagrangian thus contains fields corresponding to both the representations. For such a Lagrangian, we show that we can also define a chiral symmetry.
Estimation for entanglement negativity of free fermions
NASA Astrophysics Data System (ADS)
Herzog, Christopher P.; Wang, Yihong
2016-07-01
In this letter we study the negativity of one dimensional free fermions. We derive the general form of the {{{Z}}N} symmetric term in moments of the partial transposed (reduced) density matrix, which is an algebraic function of the end points of the system. Such a path integral turns out to be a convenient tool for making estimations for the negativity.
Observation of Weyl fermions in condensed matter
NASA Astrophysics Data System (ADS)
Ding, Hong
In 1929, a German mathematician and physicist Hermann Weyl proposed that a massless solution of the Dirac equation represents a pair of new type of particles, the so-called Weyl fermions. However, their existence in particle physics remains elusive after more than eight decades, e.g., neutrino has been regarded as a Weyl fermion in the Standard Model until it was found to have mass. Recently, significant advances in topological materials have provided an alternative way to realize Weyl fermions in condensed matter as an emergent phenomenon. Weyl semimetals are predicted as a class of topological materials that can be regarded as three-dimensional analogs of graphene breaking time reversal or inversion symmetry. Electrons in a Weyl semimetal behave exactly as Weyl fermions, which have many exotic properties, such as chiral anomaly, magnetic monopoles in the crystal momentum space, and open Fermi arcs on the surface. In this talk I will report our experimental discovery of a Weyl semimetal in TaAs by observing Fermi arcs with a characteristic spin texture in the surface states and Weyl nodes in the bulk states using angle-resolved photoemission spectroscopy.
Finite volume renormalization scheme for fermionic operators
Monahan, Christopher; Orginos, Kostas
2013-11-01
We propose a new finite volume renormalization scheme. Our scheme is based on the Gradient Flow applied to both fermion and gauge fields and, much like the Schr\\"odinger functional method, allows for a nonperturbative determination of the scale dependence of operators using a step-scaling approach. We give some preliminary results for the pseudo-scalar density in the quenched approximation.
Ideal fermion delocalization in Higgsless models
Chivukula, R. Sekhar; Simmons, Elizabeth H.; He, Hong-Jian; Kurachi, Masafumi; Tanabashi, Masaharu
2005-07-01
In this note we examine the properties of deconstructed Higgsless models for the case of a fermion whose SU(2) properties arise from delocalization over many sites of the deconstructed lattice. We derive expressions for the correlation functions and use these to establish a generalized consistency relation among correlation functions. We discuss the form of the W boson wavefunction and show that if the probability distribution of the delocalized fermions is appropriately related to the W wavefunction, then deviations in precision electroweak parameters are minimized. In particular, we show that this ''ideal fermion delocalization'' results in the vanishing of three of the four leading zero-momentum electroweak parameters defined by Barbieri et al. We then discuss ideal fermion delocalization in the context of two continuum Higgsless models, one in Anti-deSitter space and one in flat space. Our results may be applied to any Higgsless linear moose model with multiple SU(2) groups, including those with only a few extra vector bosons.
Unpaired Floquet Majorana fermions without magnetic fields
NASA Astrophysics Data System (ADS)
Reynoso, Andres A.; Frustaglia, Diego
2013-03-01
Quantum wires subject to the combined action of spin-orbit and Zeeman coupling in the presence of s-wave pairing potentials (superconducting proximity effect in semiconductors or superfluidity in cold atoms) are one of the most promising systems for the developing of topological phases hosting Majorana fermions. The breaking of time-reversal symmetry is essential for the appearance of unpaired Majorana fermions. By implementing a time-dependent spin rotation, we show that the standard magnetostatic model maps into a nonmagnetic one where the breaking of time-reversal symmetry is guaranteed by a periodical change of the spin-orbit coupling axis as a function of time. This suggests the possibility of developing the topological superconducting state of matter driven by external forces in the absence of magnetic fields and magnetic elements. From a practical viewpoint, the scheme avoids the disadvantages of conjugating magnetism and superconductivity, even though the need of a high-frequency driving of spin-orbit coupling may represent a technological challenge. We describe the basic properties of this Floquet system by showing that finite samples host unpaired Majorana fermions at their edges despite the fact that the bulk Floquet quasienergies are gapless and that the Hamiltonian at each instant of time preserves time-reversal symmetry. Remarkably, we identify the mean energy of the Floquet states as a topological indicator. We additionally show that the localized Floquet Majorana fermions are robust under local perturbations. Our results are supported by complementary numerical Floquet simulations.
Odd frequency pairing of interacting Majorana fermions
NASA Astrophysics Data System (ADS)
Huang, Zhoushen; Woelfle, Peter; Balatsky, Alexandar
Majorana fermions are rising as a promising key component in quantum computation. While the prevalent approach is to use a quadratic (i.e. non-interacting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory allowing to discuss a possible subleading admixture of even-frequency pairing. Work supported by USDOE DE-AC52-06NA25396 E304, Knut and Alice Wallenberg Foundation, and ERC DM-321031.
Flavor Constraints on Split Fermion Models
Lillie, Ben
2003-06-26
We examine the contributions to rare processes that arise in models where the Standard Model fermions are localized at distinct points in compact extra dimensions. Tree-level flavor changing neutral current interactions for the Kaluza-Klein (KK) gauge field excitations are induced in such models, and hence strong constraints are thought to exist on the size of the additional dimensions. We find a general parameterization of the model which does not depend on any specific fermion geography and show that typical values of the parameters can reproduce the fermion hierarchy pattern. Using this parameterization, we reexamine the contributions to neutral meson mixing, rare meson decays, and single top-quark production in e{sup +}e{sup -} collisions. We find that is it possible to evade the stringent bounds for natural regions of the parameters, while retaining finite separations between the fermion fields and without introducing a new hierarchy. The resulting limits on the size of the compact dimension can be as low as TeV{sup -1}.
Ideal fermion delocalization in Higgsless models
NASA Astrophysics Data System (ADS)
Chivukula, R. Sekhar; Simmons, Elizabeth H.; He, Hong-Jian; Kurachi, Masafumi; Tanabashi, Masaharu
2005-07-01
In this note we examine the properties of deconstructed Higgsless models for the case of a fermion whose SU(2) properties arise from delocalization over many sites of the deconstructed lattice. We derive expressions for the correlation functions and use these to establish a generalized consistency relation among correlation functions. We discuss the form of the W boson wavefunction and show that if the probability distribution of the delocalized fermions is appropriately related to the W wavefunction, then deviations in precision electroweak parameters are minimized. In particular, we show that this “ideal fermion delocalization” results in the vanishing of three of the four leading zero-momentum electroweak parameters defined by Barbieri et al. We then discuss ideal fermion delocalization in the context of two continuum Higgsless models, one in Anti-deSitter space and one in flat space. Our results may be applied to any Higgsless linear moose model with multiple SU(2) groups, including those with only a few extra vector bosons.
Gross, Charles
2016-01-01
Scientific misconduct has been defined as fabrication, falsification, and plagiarism. Scientific misconduct has occurred throughout the history of science. The US government began to take systematic interest in such misconduct in the 1980s. Since then, a number of studies have examined how frequently individual scientists have observed scientific misconduct or were involved in it. Although the studies vary considerably in their methodology and in the nature and size of their samples, in most studies at least 10% of the scientists sampled reported having observed scientific misconduct. In addition to studies of the incidence of scientific misconduct, this review considers the recent increase in paper retractions, the role of social media in scientific ethics, several instructional examples of egregious scientific misconduct, and potential methods to reduce research misconduct. PMID:26273897
Fermionic-mode entanglement in non-Markovian environment
Cheng, Jiong; Han, Yan; An, Qing-zhi; Zhou, Ling
2015-03-15
We evaluate the non-Markovian effects on the entanglement dynamics of a fermionic system interacting with two dissipative vacuum reservoirs. The exact solution of density matrix is derived by utilizing the Feynman–Vernon influence functional theory in the fermionic coherent state representation and the Grassmann calculus, which are valid for both the fermionic and bosonic baths, and their difference lies in the dependence of the parity of the initial states. The fermionic entanglement dynamics is presented by adding an additional restriction to the density matrix known as the superselection rules. Our analysis shows that the usual decoherence suppression schemes implemented in qubits systems can also be achieved for systems of identical fermions, and the initial state proves its importance in the evolution of fermionic entanglement. Our results provide a potential way to decoherence controlling of identical fermions.
Superfluid state of repulsively interacting three-component fermionic atoms in optical lattices
NASA Astrophysics Data System (ADS)
Suga, Sei-Ichiro; Inaba, Kensuke
2013-03-01
We investigate the superfluid state of repulsively interacting three-component (color) fermionic atoms in optical lattices using Feynman diagrammatic approaches and the dynamical mean field theory. When the anisotropy of the three repulsive interactions is strong, atoms of two of the three colors form Cooper pairs and atoms of the third color remain a Fermi liquid. This superfluid emerges close to half filling at which the Mott insulating state characteristic of the three-component repulsive fermions appears. An effective attractive interaction is induced by density fluctuations of the third-color atoms. The superfluid state is stable against the phase separation that occurs in the strongly repulsive region. We determine the phase diagrams in terms of temperature, filling, and the anisotropy of the repulsive interactions. This work was supported by Grant-in-Aid for Scientific Research (C) (No. 23540467) from the Japan Society for the Promotion of Science.
NASA Astrophysics Data System (ADS)
Xiang-Guo, Meng; Ji-Suo, Wang; Hong-Yi, Fan; Cheng-Wei, Xia
2016-04-01
We solve the fermionic master equation for a thermal bath to obtain its explicit Kraus operator solutions via the fermionic state approach. The normalization condition of the Kraus operators is proved. The matrix representation for these solutions is obtained, which is incongruous with the result in the book completed by Nielsen and Chuang [Quantum Computation and Quantum Information, Cambridge University Press, 2000]. As especial cases, we also present the Kraus operator solutions to master equations for describing the amplitude-decay model and the diffusion process at finite temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11347026), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2013AM012 and ZR2012AM004), and the Research Fund for the Doctoral Program and Scientific Research Project of Liaocheng University, Shandong Province, China.
Utilizing Traditional Knowledge in a Scientific Setting.
ERIC Educational Resources Information Center
Boyne, Grace M.
2003-01-01
A nuclear physicist feels that his Navajo upbringing, with its emphasis on the structure of nature and abstract reasoning, prepared him well for the world of physics. Traditional Navajo sandpaintings helped him understand physics concepts. Native American students show strengths in learning visual, perceptual, or spatial information, and they…
Exact holographic mapping in free fermion systems
NASA Astrophysics Data System (ADS)
Lee, Ching Hua; Qi, Xiao-Liang
2016-01-01
In this paper, we perform a detailed analysis of the exact holographic mapping first introduced in arXiv:1309.6282, which was proposed as an explicit example of holographic duality between quantum many-body systems and gravitational theories. We obtain analytic results for free fermion systems that not only confirm previous numerical results, but also elucidate the exact relationships between the various physical properties of the bulk and boundary systems. These analytic results allow us to study the asymptotic properties that are difficult to probe numerically, such as the near-horizon regime of the black-hole geometry. We shall also explore a few interesting but hitherto unexplored bulk geometries, such as that corresponding to a boundary critical fermion with a nontrivial dynamical critical exponent. Our analytic framework also allows us to study the holographic mapping of some of these boundary theories in dimensions 2+1 or higher.
A closer look at the elementary fermions
Goldhaber, Maurice
2002-01-01
Although there have been many experimental and theoretical efforts to measure and interpret small deviations from the standard model of particle physics, the gap that the model leaves in understanding why there are only three generations of the elementary fermions, with hierarchical masses, has not received the attention it deserves. I present here an attempt to fill this gap. Although our findings are mostly only qualitative, they nevertheless may be of heuristic value. Rules concerning the elementary fermions, some previously known and some new, lead to a number of conclusions and questions that seem worth pursuing. Some clarify the standard model, and others suggest possible modifications, the implications of which are discussed. PMID:11773637
Functional representation for fermionic quantum fields
NASA Astrophysics Data System (ADS)
Floreanini, R.; Jackiw, R.
1988-04-01
A functional representation for fermionic quantum fields is developed in analogy to familiar results for bosonic fields. The infinite Clifford algebra of the field anticommutator is realized reducibly on a Grassmann functional space. On this space, transformation groups may be represented without normal ordering with respect to a Fock vacuum, and a projective representation for the two-dimensional conformal group is found, which is compared to the corresponding representation in terms of bosonic fields. When a quadratic Hamiltonian for the Fermi fields is posited, a Fock space can be constructed after a prescription for filling the Dirac sea is selected. Different filling prescriptions lead to inequivalent Fock spaces within the functional space. Explicit eigenfunctionals exhibit the peculiarities of fermionic field theory, such as fractional charge, Berry's phase, and anomalies.
Peltier cooling of fermionic quantum gases.
Grenier, Ch; Georges, A; Kollath, C
2014-11-14
We propose a cooling scheme for fermionic quantum gases, based on the principles of the Peltier thermoelectric effect and energy filtering. The system to be cooled is connected to another harmonically trapped gas acting as a reservoir. The cooling is achieved by two simultaneous processes: (i) the system is evaporatively cooled, and (ii) cold fermions from deep below the Fermi surface of the reservoir are injected below the Fermi level of the system, in order to fill the "holes" in the energy distribution. This is achieved by a suitable energy dependence of the transmission coefficient connecting the system to the reservoir. The two processes can be viewed as simultaneous evaporative cooling of particles and holes. We show that both a significantly lower entropy per particle and faster cooling rate can be achieved in this way than by using only evaporative cooling. PMID:25432033
Ultrasoft fermionic excitation at finite chemical potential
NASA Astrophysics Data System (ADS)
Blaizot, Jean-Paul; Satow, Daisuke
2014-05-01
It has been suggested previously that an ultrasoft fermionic excitation develops, albeit with a small spectral weight, in a system of massless fermions and scalar bosons with Yukawa interaction at high temperature T. In this paper we study how this excitation is modified at finite chemical potential μ. We relate the existence of the ultrasoft mode to symmetries, in particular charge conjugation, and a supersymmetry of the free system which is spontaneously broken by finite temperature and finite density effects, as argued earlier by Lebedev and Smilga. A nonvanishing chemical potential breaks both symmetries explicitly and maximally at zero temperature where the mode ceases to exist. A detailed calculation indicates that the ultrasoft excitation persists as long as T≥0.71μ.
Playing with fermion couplings in Higgsless models
Casalbuoni, R.; De Curtis, S.; Dolce, D.; Dominici, D.
2005-04-01
We discuss the fermion couplings in a four dimensional SU(2) linear moose model by allowing for direct couplings between the left-handed fermions on the boundary and the gauge fields in the internal sites. This is realized by means of a product of nonlinear {sigma}-model scalar fields which, in the continuum limit, is equivalent to a Wilson line. The effect of these new nonlocal couplings is a contribution to the {epsilon}{sub 3} parameter which can be of opposite sign with respect to the one coming from the gauge fields along the string. Therefore, with some fine-tuning, it is possible to satisfy the constraints from the electroweak data.
Fermionic field theory for trees and forests.
Caracciolo, Sergio; Jacobsen, Jesper Lykke; Saleur, Hubert; Sokal, Alan D; Sportiello, Andrea
2004-08-20
We prove a generalization of Kirchhoff's matrix-tree theorem in which a large class of combinatorial objects are represented by non-Gaussian Grassmann integrals. As a special case, we show that unrooted spanning forests, which arise as a q-->0 limit of the Potts model, can be represented by a Grassmann theory involving a Gaussian term and a particular bilocal four-fermion term. We show that this latter model can be mapped, to all orders in perturbation theory, onto the N-vector model at N=-1 or, equivalently, onto the sigma model taking values in the unit supersphere in R(1|2). It follows that, in two dimensions, this fermionic model is perturbatively asymptotically free. PMID:15447166
A Quantum Gas Microscope for Fermionic Potassium
NASA Astrophysics Data System (ADS)
Cheuk, Lawrence; Nichols, Matthew; Okan, Melih; Lawrence, Katherine; Zhang, Hao; Zwierlein, Martin
2016-05-01
Ultracold atoms in optical lattices have enabled experimental studies of quantum many-body physics in Hubbard-type lattice systems in a clean and well-controlled environment. In particular, the advent of quantum gas microscopes has made available new experimental probes ideally suited for observing magnetic order and spatial correlations. In the past year, several groups, including ours, first realized quantum gas microscopes for fermionic atoms. In this talk, we describe our experimental setup, which combines high-resolution imaging with Raman sideband cooling to achieve single-site-resolved fluorescent imaging of fermionic 40 K atoms. We also report on recent progress towards observing quantum phases of the Fermi-Hubbard model with single-site resolution.
Unextendible product basis for fermionic systems
NASA Astrophysics Data System (ADS)
Chen, Jianxin; Chen, Lin; Zeng, Bei
2014-08-01
We discuss the concept of unextendible product basis (UPB) and generalized UPB for fermionic systems, using Slater determinants as an analogue of product states, in the anti-symmetric subspace wedge ^ N {{C}}^M. We construct an explicit example of generalized fermionic unextendible product basis (FUPB) with minimum cardinality N(M - N) + 1 for any N ⩾ 2, M ⩾ 4. We also show that any bipartite anti-symmetric space wedge ^ 2 {{C}}^M of codimension two is spanned by Slater determinants, and the spaces of higher codimension may not be spanned by Slater determinants. Furthermore, we construct an example of complex FUPB of N = 2, M = 4 with minimum cardinality 5. In contrast, we show that a real FUPB does not exist for N = 2, M = 4. Finally, we provide a systematic construction for FUPBs of higher dimensions by using FUPBs and UPBs of lower dimensions.
Explicit Hamiltonians inducing volume law for entanglement entropy in fermionic lattices
NASA Astrophysics Data System (ADS)
Gori, Giacomo; Paganelli, Simone; Sharma, Auditya; Sodano, Pasquale; Trombettoni, Andrea
2015-06-01
We show how the area law for entanglement entropy may be violated by free fermions on a lattice, and we look for conditions leading to the emergence of a volume law. We give an explicit construction of the states with maximal entanglement entropy based on the fact that, once a bipartition of the lattice in two complementary sets A and A ¯ is given, the states with maximal entanglement entropy (volume law) may be factored into Bell pairs (BPs) formed by two states with support on A and A ¯. We then exhibit, for translational invariant fermionic systems on a lattice, a Hamiltonian whose ground state is such that it yields an exact volume law. As expected, the corresponding Fermi surface has a fractal topology. We also provide some examples of fermionic models for which the ground state may have an entanglement entropy SA between the area and the volume law, building an explicit example of a one-dimensional free fermion model where SA(L ) ∝Lβ , with β being intermediate between β =0 (area law) and β =1 (BP state inducing volume law). For this model, the dispersion relation has a "zigzag" structure leading to a fractal Fermi surface whose counting box dimension equals, for large lattices, β . Our analysis clearly relates the violation of the area law for the entanglement entropy of the ground state to the emergence of a nontrivial topology of the Fermi surface.
Sen, Aditi; Sen, Ujjwal; Gromek, Bartosz; Lewenstein, Maciej
2007-02-15
We consider information transmission through a noiseless quantum channel, where the information is encoded into massive indistinguishable particles: bosons or fermions. We study the situation in which the particles are noninteracting. The encoding input states obey a set of physically motivated constraints on the mean values of the energy and particle number. In such a case, the determination of both classical and quantum capacity reduces to a constrained maximization of entropy. In the case of noninteracting bosons, signatures of Bose-Einstein condensation can be observed in the behavior of the capacity. A major motivation for these considerations is to compare the information-carrying capacities of channels that carry bosons with those that carry fermions. We show analytically that fermions generally provide higher channel capacity, i.e., they are better suited for transferring bits as well as qubits, in comparison to bosons. This holds for a large range of power-law potentials, and for moderate to high temperatures. Numerical simulations seem to indicate that the result holds for all temperatures. Also, we consider the low-temperature behavior for the three-dimensional box and harmonic trap, and again we show that the fermionic capacity is higher than the bosonic one for sufficiently low temperatures.
Strong coupling QED with two fermionic flavors
Wang, K.C.
1990-11-01
We report the recent results of our simulation of strong coupling QED, with non-compact action, on lattices 10{sup 4} and 16{sup 4}. Since we are dealing with two staggered fermionic flavors, we use hybrid algorithm to do the simulation. In addition to the measurement of the chiral order parameter {l angle}{bar {psi}}{psi}{r angle}, we also measure magnetic monopole susceptibility, {chi}, throughout the region of chiral transition. 6 refs., 6 figs.
Point contact spectroscopy of heavy fermions
NASA Astrophysics Data System (ADS)
Moser, M.; Wachter, P.; Franse, J. J. M.; Meisner, G. P.; Walker, E.
Point contact spectroscopy (PCS) has been performed on the heavy fermion systems CeAl3, CeCu6, UPt3, U6Co and U2PtC2. The dynamical resistance dU/dI is a function of the electronic density of states (EDS) at E/sub F/. The width of the EDS inferred from the PC measurements can be compared with the (GAMMA)-value of the specific heat.
Magnetization of planar four-fermion systems
Caldas, Heron; Ramos, Rudnei O.
2009-09-15
We consider a planar system of fermions, at finite temperature and density under a static magnetic field parallel to the two-dimensional plane. This magnetic field generates a Zeeman effect and then a spin polarization of the system. The critical properties are studied from the Landau's free energy. The possible observable consequences of the magnetization of planar systems such as polymer films and graphene are discussed.
Fermion masses from SO(10) Hermitian matrices
Moorhouse, R. G.
2008-03-01
Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126 scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.
Fermion masses from SO(10) Hermitian matrices
NASA Astrophysics Data System (ADS)
Moorhouse, R. G.
2008-03-01
Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126¯ scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.
Renormalization group for non-relativistic fermions.
Shankar, R
2011-07-13
A brief introduction is given to the renormalization group for non-relativistic fermions at finite density. It is shown that Landau's theory of the Fermi liquid arises as a fixed point (with the Landau parameters as marginal couplings) and its instabilities as relevant perturbations. Applications to related areas, nuclear matter, quark matter and quantum dots, are briefly discussed. The focus will be on explaining the main ideas to people in related fields, rather than addressing the experts. PMID:21646269
ERIC Educational Resources Information Center
Goodstein, David
1991-01-01
A discussion of fraud in the presentation of results of scientific research cites cases looks at variations in the degree of misrepresentation, kinds and intents of fraud, attention given by public agencies (National Institutes of Health, National Science Foundation, Public Health Service), and differences between scientific and civil fraud. (MSE)
Strong CP, Flavor, and Twisted Split Fermions
Harnik, Roni; Perez, Gilad; Schwartz, Matthew D.; Shirman, Yuri
2004-11-10
We present a natural solution to the strong CP problem in the context of split fermions. By assuming CP is spontaneously broken in the bulk, a weak CKM phase is created in the standard model due to a twisting in flavor space of the bulk fermion wavefunctions. But the strong CP phase remains zero, being essentially protected by parity in the bulk and CP on the branes. As always in models of spontaneous CP breaking, radiative corrections to theta bar from the standard model are tiny, but even higher dimension operators are not that dangerous. The twisting phenomenon was recently shown to be generic, and not to interfere with the way that split fermions naturally weaves small numbers into the standard model. It follows that out approach to strong CP is compatible with flavor, and we sketch a comprehensive model. We also look at deconstructed version of this setup which provides a viable 4D model of spontaneous CP breaking which is not in the Nelson-Barr class.
Rotating fermions inside a cylindrical boundary
NASA Astrophysics Data System (ADS)
Ambruş, Victor E.; Winstanley, Elizabeth
2016-05-01
We study a quantum fermion field inside a cylinder in Minkowski space-time. On the surface of the cylinder, the fermion field satisfies either spectral or MIT bag boundary conditions. We define rigidly-rotating quantum states in both cases, assuming that the radius of the cylinder is sufficiently small that the speed-of-light surface is excluded from the space-time. With this assumption, we calculate rigidly-rotating thermal expectation values of the fermion condensate, neutrino charge current and stress-energy tensor relative to the bounded vacuum state. These rigidly-rotating thermal expectation values are finite everywhere inside and on the surface of the cylinder, and their detailed properties depend on the choice of boundary conditions. We also compute the Casimir divergence of the expectation values of these quantities in the bounded vacuum state relative to the unbounded Minkowski vacuum. We find that the rate of divergence of the Casimir expectation values depends on the conditions imposed on the boundary.
Composite gauge-bosons made of fermions
NASA Astrophysics Data System (ADS)
Suzuki, Mahiko
2016-07-01
We construct a class of Abelian and non-Abelian local gauge theories that consist only of matter fields of fermions. The Lagrangian is local and does not contain an auxiliary vector field nor a subsidiary condition on the matter fields. It does not involve an extra dimension nor supersymmetry. This Lagrangian can be extended to non-Abelian gauge symmetry only in the case of SU(2) doublet matter fields. We carry out an explicit diagrammatic computation in the leading 1 /N order to show that massless spin-one bound states appear with the correct gauge coupling. Our diagram calculation exposes the dynamical features that cannot be seen in the formal auxiliary vector-field method. For instance, it shows that the s -wave fermion-antifermion interaction in the 3S1 channel (ψ ¯ γμψ ) alone cannot form the bound gauge bosons; the fermion-antifermion pairs must couple to the d -wave state too. One feature common to our class of Lagrangian is that the Noether current does not exist. Therefore it evades possible conflict with the no-go theorem of Weinberg and Witten on the formation of the non-Abelian gauge bosons.
Scalar meson spectroscopy with lattice staggered fermions
Bernard, Claude; DeTar, Carleton; Fu Ziwen; Prelovsek, Sasa
2007-11-01
With sufficiently light up and down quarks the isovector (a{sub 0}) and isosinglet (f{sub 0}) scalar meson propagators are dominated at large distance by two-meson states. In the staggered-fermion formulation of lattice quantum chromodynamics, taste-symmetry breaking causes a proliferation of two-meson states that further complicates the analysis of these channels. Many of them are unphysical artifacts of the lattice approximation. They are expected to disappear in the continuum limit. The staggered-fermion fourth-root procedure has its purported counterpart in rooted staggered chiral perturbation theory (rS{chi}PT). Fortunately, the rooted theory provides a strict framework that permits the analysis of scalar meson correlators in terms of only a small number of low-energy couplings. Thus the analysis of the point-to-point scalar meson correlators in this context gives a useful consistency check of the fourth-root procedure and its proposed chiral realization. Through numerical simulation we have measured correlators for both the a{sub 0} and f{sub 0} channels in the 'Asqtad' improved staggered-fermion formulation in a lattice ensemble with lattice spacing a=0.12 fm. We analyze those correlators in the context of rS{chi}PT and obtain values of the low-energy chiral couplings that are reasonably consistent with previous determinations.
The Feynman problem and fermionic entanglement: Fermionic theory versus qubit theory
NASA Astrophysics Data System (ADS)
D'Ariano, Giacomo Mauro; Manessi, Franco; Perinotti, Paolo; Tosini, Alessandro
2014-06-01
The present paper is both a review on the Feynman problem, and an original research presentation on the relations between Fermionic theories and qubits theories, both regarded in the novel framework of operational probabilistic theories. The most relevant results about the Feynman problem of simulating Fermions with qubits are reviewed, and in the light of the new original results, the problem is solved. The answer is twofold. On the computational side, the two theories are equivalent, as shown by Bravyi and Kitaev [S. B. Bravyi and A. Y. Kitaev, Ann. Phys. 298, 210 (2002)]. On the operational side, the quantum theory of qubits and the quantum theory of Fermions are different, mostly in the notion of locality, with striking consequences on entanglement. Thus the emulation does not respect locality, as it was suspected by Feynman [R. Feynman, Int. J. Theor. Phys. 21, 467 (1982)].
Mixtures of Bosonic and Fermionic atoms
NASA Astrophysics Data System (ADS)
Albus, Alexander
2003-12-01
The theory of atomic Boson-Fermion mixtures in the dilute limit beyond mean-field is considered in this thesis. Extending the formalism of quantum field theory we derived expressions for the quasi-particle excitation spectra, the ground state energy, and related quantities for a homogenous system to first order in the dilute gas parameter. In the framework of density functional theory we could carry over the previous results to inhomogeneous systems. We then determined to density distributions for various parameter values and identified three different phase regions: (i) a stable mixed regime, (ii) a phase separated regime, and (iii) a collapsed regime. We found a significant contribution of exchange-correlation effects in the latter case. Next, we determined the shift of the Bose-Einstein condensation temperature caused by Boson-Fermion interactions in a harmonic trap due to redistribution of the density profiles. We then considered Boson-Fermion mixtures in optical lattices. We calculated the criterion for stability against phase separation, identified the Mott-insulating and superfluid regimes both, analytically within a mean-field calculation, and numerically by virtue of a Gutzwiller Ansatz. We also found new frustrated ground states in the limit of very strong lattices. ----Anmerkung: Der Autor ist Träger des durch die Physikalische Gesellschaft zu Berlin vergebenen Carl-Ramsauer-Preises 2004 für die jeweils beste Dissertation der vier Universitäten Freie Universität Berlin, Humboldt-Universität zu Berlin, Technische Universität Berlin und Universität Potsdam. Ziel der Arbeit war die systematische theoretische Behandlung von Gemischen aus bosonischen und fermionischen Atomen in einem Parameterbereich, der sich zur Beschreibung von aktuellen Experimenten mit ultra-kalten atomaren Gasen eignet. Zuerst wurde der Formalismus der Quantenfeldtheorie auf homogene, atomare Boson-Fermion Gemische erweitert, um grundlegende Größen wie Quasiteilchenspektren
Scientific Globish versus scientific English.
Tychinin, Dmitry N; Kamnev, Alexander A
2013-10-01
The proposed adoption of 'scientific Globish' as a simplified language standard for scholarly communication may appeal to authors who have difficulty with English proficiency. However, Globish might not justify the hopes being pinned on it and might open the door to further deterioration of the quality of English-language scientific writing. PMID:23928006
Trapped resonant fermions above the superfluid transition temperature
Cheng, C.-H.; Yip, S.-K.
2007-01-01
We investigate trapped resonant fermions with unequal populations within the local density approximation above the superfluid transition temperature. By tuning the attractive interaction between fermions via Feshbach resonance, the system evolves from weakly interacting fermi gas to strongly interacting fermi gas, and finally becomes a Bose-Fermi mixture. The density profiles of fermions are examined and compared with experiments. We also point out the simple relationships between the local density, the axial density, and the gas pressure within the local density approximation.
Semiclassical fermion pair creation in de Sitter spacetime
Stahl, Clément Eckhard, Strobel
2015-12-17
We present a method to semiclassically compute the pair creation rate of bosons and fermions in de Sitter spacetime. The results in the bosonic case agree with the ones in the literature. We find that for the constant electric field the fermionic and bosonic pair creation rate are the same. This analogy of bosons and fermions in the semiclassical limit is known from several flat spacetime examples.
Drone-fermions in the two-dimensional antiferromagnet
NASA Astrophysics Data System (ADS)
Krivenko, S.; Khaliullin, G.
1995-02-01
Two different representations of spins - via the conventional fermions, or via the Mattis drone-fermions - are compared considering the planar antiferromagnetic Heisenberg model as an example. Mean-field spin correlation functions calculated for the uniform and flux RVB states show that the drone-fermion approach has an advantage in giving the lower energy and the enhanced AF correlations, because of the absence of unphysical spinless states in this representation.
NASA Astrophysics Data System (ADS)
de Vega, H. J.; Medrano, M. Ramon; Sanchez, N.
1992-07-01
We investigate the physical implications and particle content of superstring scattering in the supergravity shock-wave background recently found by us. The amplitudes for the different particle transmutation processes taking place in this geometry are explicitly computed for Gree-Schwarz superstring, including the new phenomena of fermion to boson and boson to fermion transmutations. Transition amplitudes among the ground states, first and second excited states are obtained. Particularly interesting are the amplitudes within the massless particle sector, which lead to physical massive particles upon supersymmetry breaking at low energies.
Quantum Hall Effect of Massless Dirac Fermions and Free Fermions in Hofstadter's Butterfly
NASA Astrophysics Data System (ADS)
Yoshioka, Nobuyuki; Matsuura, Hiroyasu; Ogata, Masao
2016-06-01
We propose a new physical interpretation of the Diophantine equation of σxy for the Hofstadter problem. First, we divide the energy spectrum, or Hofstadter's butterfly, into smaller self-similar areas called "subcells", which were first introduced by Hofstadter to describe the recursive structure. We find that in the energy gaps between subcells, there are two ways to account for the quantization rule of σxy, that are consistent with the Diophantine equation: Landau quantization of (i) massless Dirac fermions or (ii) free fermions in Hofstadter's butterfly.
Fermion frontiers in vector lattice gauge theories: Proceedings. Volume 8
1998-11-01
The inclusion of fermions into simulations of lattice gauge theories is very difficult both theoretically and numerically. With the presence of Teraflops-scale computers for lattice gauge theory, the authors wanted a forum to discuss new approaches to lattice fermions. The workshop concentrated on approaches which are ripe for study on such large machines. Although lattice chiral fermions are vitally important to understand, there is not technique at hand which is viable on these Teraflops-scale machines for real-world problems. The discussion was therefore focused on recent developments and future prospects for QCD-like theories. For the well-known fermion formulations, the Aoki phase in Wilson fermions, novelties of U{sub A}(1) symmetry and the {eta}{prime} for staggered fermions and new approaches for simulating the determinant for Wilson fermions were discussed. The newer domain-wall fermion formulation was reviewed, with numerical results given by many speakers. The fermion proposal of Friedberg, Lee and Pang was introduced. They also were able to compare and contrast the dependence of QCD and QCD-like SUSY theories on the number of quark flavors. These proceedings consist of several transparencies and a summary page from each speaker. This should serve to outline the major points made in each talk.
Four-fermion interaction from torsion as dark energy
NASA Astrophysics Data System (ADS)
Popławski, Nikodem J.
2012-02-01
The observed small, positive cosmological constant may originate from a four-fermion interaction generated by the spin-torsion coupling in the Einstein-Cartan-Sciama-Kibble gravity if the fermions are condensing. In particular, such a condensation occurs for quark fields during the quark-gluon/hadron phase transition in the early Universe. We study how the torsion-induced four-fermion interaction is affected by adding two terms to the Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the curvature tensor and a spinor-bilinear scalar density which measures the nonminimal coupling of fermions to torsion.
Wilson Fermions and Axion Electrodynamics in Optical Lattices
Bermudez, A.; Martin-Delgado, M. A.; Mazza, L.; Rizzi, M.; Goldman, N.; Lewenstein, M.
2010-11-05
We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.
Chiral lattice fermions with correct vacuum polarization and chiral anomaly
Pryor, C. )
1991-04-15
An action for chiral lattice fermions is proposed, which avoids the Nielsen-Ninomiya theorem by virtue of its nonlocality and nonbilinearity. The action is constructed by eliminating the extra fermion modes with a gauge-violating Majorana-type Wilson mass, which is then rendered invariant by an integration over gauge transformations. The free propagator is calculated, and the one-loop vacuum polarization is shown to be identical to that for Wilson fermions, even at nonzero lattice spacing. Also the chiral anomaly is shown to be the same as for Wilson fermions in the continuum limit.
ERIC Educational Resources Information Center
Goodstein, David
2002-01-01
Explores scientific fraud, asserting that while few scientists actually falsify results, the field has become so competitive that many are misbehaving in other ways; an example would be unreasonable criticism by anonymous peer reviewers. (EV)
Continuum regularization of gauge theory with fermions
Chan, H.S.
1987-03-01
The continuum regularization program is discussed in the case of d-dimensional gauge theory coupled to fermions in an arbitrary representation. Two physically equivalent formulations are given. First, a Grassmann formulation is presented, which is based on the two-noise Langevin equations of Sakita, Ishikawa and Alfaro and Gavela. Second, a non-Grassmann formulation is obtained by regularized integration of the matter fields within the regularized Grassmann system. Explicit perturbation expansions are studied in both formulations, and considerable simplification is found in the integrated non-Grassmann formalism.
Boson formulation of fermion field theories
Ha, Y.K.
1984-04-15
The nonperturbative connection between a canonical Fermi field and a canonical Bose field in two dimensions is developed and its validity verified according to the tenets of quantum field theory. We advocate the point of view that a boson formulation offers a unifying theme in understanding the structure of many theories. This is illustrated by the boson formulation of a multifermion theory with chiral and internal symmetries. Many features of the massless theory, such as dynamical mass generation with asymptotic-freedom behavior, hidden chiral symmetry, and connections with models of apparently different internal symmetries, are readily transparent through such fermion-boson metamorphosis.
Discovering correlated fermions using quantum Monte Carlo.
Wagner, Lucas K; Ceperley, David M
2016-09-01
It has become increasingly feasible to use quantum Monte Carlo (QMC) methods to study correlated fermion systems for realistic Hamiltonians. We give a summary of these techniques targeted at researchers in the field of correlated electrons, focusing on the fundamentals, capabilities, and current status of this technique. The QMC methods often offer the highest accuracy solutions available for systems in the continuum, and, since they address the many-body problem directly, the simulations can be analyzed to obtain insight into the nature of correlated quantum behavior. PMID:27518859
8B structure in Fermionic Molecular Dynamics
NASA Astrophysics Data System (ADS)
Henninger, K. R.; Neff, T.; Feldmeier, H.
2015-04-01
The structure of the light exotic nucleus 8B is investigated in the Fermionic Molecular Dynamics (FMD) model. The decay of 8B is responsible for almost the entire high- energy solar-neutrino flux, making structure calculations of 8B important for determining the solar core temperature. 8B is a proton halo candidate thought to exhibit clustering. FMD uses a wave-packet basis and is well-suited for modelling clustering and halos. For a multiconfiguration treatment we construct the many-body Hilbert space from antisymmetrised angular-momentum projected 8-particle states. First results show formation of a proton halo.
Discovering correlated fermions using quantum Monte Carlo
NASA Astrophysics Data System (ADS)
Wagner, Lucas K.; Ceperley, David M.
2016-09-01
It has become increasingly feasible to use quantum Monte Carlo (QMC) methods to study correlated fermion systems for realistic Hamiltonians. We give a summary of these techniques targeted at researchers in the field of correlated electrons, focusing on the fundamentals, capabilities, and current status of this technique. The QMC methods often offer the highest accuracy solutions available for systems in the continuum, and, since they address the many-body problem directly, the simulations can be analyzed to obtain insight into the nature of correlated quantum behavior.
Complete Boson-Fermion Model of Superconductivity
NASA Astrophysics Data System (ADS)
de Llano, Manuel
2003-03-01
The unification of the 1957 BCS theory with that of Bose-Einstein condensation (BEC) that gives roughly good first-principles transition temperature Tc predictions in either 2D or 3D for all of the ``Uemura plot'' ``exotic'' or conventional superconductors without abandoning the much-maligned phonon interaction mechanism has recently been achieved [1]-[3]. The same dynamical mechanism also allows for room-temperature superconductivity. The only condition is that one depart moderately from the perfect electron (e)-/hole (h)-Cooper-pair (CP) symmetry to which BCS (and indeed also the somewhat more general BCS-Bose crossover) theory are restricted by construction. It now becomes feasible to explain, among other things, why largely all superconductors empirically have substantially higher T_c's if their normal-state charge carriers are holes rather than electrons. A complete (in the sense that 2h-CPs are not ignored) boson-fermion model (CBFM) has been developed that reduces in the appropriate special cases to: a) ordinary BCS theory for weak boson-fermion coupling; b) the BCS-Bose ``crossover'' theory dating back to 1967; and, for no 2h-CPs to: c) the 1989 boson-fermion (BF) BEC model by T.D. Lee et al. of superconductors which without 2h-CPs is unrelated to BCS theory; d) an ideal BF binary-gas model [4] predicting nonzero BEC T_c's even in 2D; and finally to e) ordinary BEC (1925). The CBFM is a BF statistical model similar to those developed in the mid-50's by Schafroth, Blatt & Butler but which now includes 2h-CPs on an equal footing with 2e-CPs, and which unlike these models also contains the empirically well-established fermionic energy gap. [1] V.V. Tolmachev, Phys. Lett. A 266, 400 (2000). [2] M. Fortes, M.A. Solis, M. de Llano & V.V. Tolmachev, Physica C 364, 95 (2001). [3] M. de Llano & V.V. Tolmachev, Physica A 317, 546 (2003). [4] M. Casas, N.J. Davidson, M. de Llano, T.A. Mamedov, A. Puente, R.M. Quick, A. Rigo & M.A. Solis, Physica A 295, 146 (2001
Generating functions for canonical systems of fermions.
Pain, Jean-Christophe; Gilleron, Franck; Porcherot, Quentin
2011-06-01
The method proposed by Pratt to derive recursion relations for systems of degenerate fermions [S. Pratt, Phys. Rev. Lett. 84, 4255 (2000)] relies on diagrammatic techniques. This efficient formalism assumes no explicit two-body interactions, makes possible the inclusion of conservation laws, and requires low computational time. In this Brief Report, we show that such recursion relations can be obtained from generating functions, without any restriction in relation to the number of conservation laws (e.g., total energy or angular momentum). PMID:21797523
Some Improved Nonperturbative Bounds for Fermionic Expansions
NASA Astrophysics Data System (ADS)
Lohmann, Martin
2016-06-01
We reconsider the Gram-Hadamard bound as it is used in constructive quantum field theory and many body physics to prove convergence of Fermionic perturbative expansions. Our approach uses a recursion for the amplitudes of the expansion, discovered in a model problem by Djokic (2013). It explains the standard way to bound the expansion from a new point of view, and for some of the amplitudes provides new bounds, which avoid the use of Fourier transform, and are therefore superior to the standard bounds for models like the cold interacting Fermi gas.
Zero-point energy of confined fermions
Milton, K.A.
1980-01-01
A closed form for the reduced Green's function of massless fermions in the interior of a spherical bag is obtained. In terms of this Green's function, the corresponding zero-point or Casimir energy is computed. It is proposed that a resulting quadratic divergence can be absorbed by renormalizing a suitable parameter in the bag model (that is, absorbed by a contact term). The residual Casimir stress is attractive, but smaller than the repulsive Casimir stress of gluons in the model. The result for the total zero-point energy is in substantial disagreement with bag model phenomenological values.
Elementary formula for entanglement entropies of fermionic systems
Levay, Peter; Nagy, Szilvia; Pipek, Janos
2005-08-15
An elementary formula for the von Neumann and Renyi entropies describing quantum correlations in two-fermionic systems having four single-particle states is presented. An interesting geometric structure of fermionic entanglement is revealed. A connection with the generalized Pauli principle is established.
Reducing finite lattice spacing errors for staggered fermions
NASA Astrophysics Data System (ADS)
Luo, Yubing
1998-12-01
In this thesis we study on-shell-improved lattice QCD with staggered fermions using Symanzik's improvement program. We present a complete and detailed discussion of the finite lattice spacing corrections to staggered fermion matrix elements. Expanding upon arguments of Sharpe, we explicitly implement the Symanzik improvement program demonstrating the absence of order a terms in the on-shell-improved action. We propose a general program to improve fermion operators to remove all O(a) corrections from their matrix elements, and demonstrate this program for the examples of matrix elements of fermion bilinears and BK. We find the former does have O(a) corrections while the latter does not. Also, we give an explicit form of lattice currents which are accurate to order a2 at the tree-level. Furthermore, we find that there are as many as 15 independent lattice operators of dimension-6 (including both gauge and fermion operators) which must be added to the unimproved action to form an O(a2)-improved action. Among them, the total number of dimension-6 gauge operators and fermion bilinears is 5. The other ten terms are four- fermion operators. At the tree level and tadpole-improved tree level, all ten four-fermion operators are absent.
A streamlined method for chiral fermions on the lattice
Bodwin, G.T. . High Energy Physics Div.); Kovacs, E.V. )
1992-11-10
We discussed the use of renormalization counterterms to restore the chiral gauge symmetry in a lattice theory of Wilson fermions. We show that a large class of counterterms can be implemented automatically by making a simple modification to the fermion determinant.
Charged fermions tunneling from accelerating and rotating black holes
Rehman, Mudassar; Saifullah, K. E-mail: saifullah@qau.edu.pk
2011-03-01
We study Hawking radiation of charged fermions from accelerating and rotating black holes with electric and magnetic charges. We calculate the tunneling probabilities of incoming and outgoing fermionic particles and find the Hawking temperature of these black holes. We also provide an explicit expression of the classical action for the massive and massless particles in the background of these black holes.
Kink modes and effective four dimensional fermion and Higgs brane models
George, Damien P.; Volkas, Raymond R.
2007-05-15
In the construction of a classical smoothed out brane world model in five dimensions, one uses a dynamically generated domain wall (a kink) to localize an effective four dimensional theory. At the level of the Euler-Lagrange equations the kink sets up a potential well, a mechanism which has been employed extensively to obtain localized, four dimensional, massless chiral fermions. We present the generalization of this kink trapping mechanism for both scalar and fermionic fields, and retain all degrees of freedom that were present in the higher dimensional theory. We show that a kink background induces a symmetric modified Poeschl-Teller potential well, and give explicit analytic forms for all the bound modes and a restricted set of the continuum modes. We demonstrate that it is possible to confine an effective four dimensional scalar field with a quartic potential of arbitrary shape. This can be used to place the standard model electroweak Higgs field on the brane, and also generate nested kink solutions. We also consider the limits of the parameters in the theory which give thin kinks and localized and delocalized scalar and fermionic fields.
Weinberg, A.M.
1997-12-01
Today, for the first time, scientific concerns are seriously being addressed that span future times--hundreds, even thousands, or more years in the future. One is witnessing what the author calls scientific millenarianism. Are such concerns for the distant future exercises in futility, or are they real issues that, to the everlasting gratitude of future generations, this generation has identified, warned about and even suggested how to cope with in the distant future? Can the four potential catastrophes--bolide impact, CO{sub 2} warming, radioactive wastes and thermonuclear war--be avoided by technical fixes, institutional responses, religion, or by doing nothing? These are the questions addressed in this paper.
NASA Astrophysics Data System (ADS)
Hoelbling, Christian; Zielinski, Christian
2016-07-01
We follow up on a suggestion by Adams and construct explicit domain wall fermion operators with staggered kernels. We compare different domain wall formulations, namely the standard construction as well as Boriçi's modified and Chiu's optimal construction, utilizing both Wilson and staggered kernels. In the process, we generalize the staggered kernels to arbitrary even dimensions and introduce both truncated and optimal staggered domain wall fermions. Some numerical investigations are carried out in the (1 +1 )-dimensional setting of the Schwinger model, where we explore spectral properties of the bulk, effective and overlap Dirac operators in the free-field case, on quenched thermalized gauge configurations and on smooth topological configurations. We compare different formulations using the effective mass, deviations from normality and violations of the Ginsparg-Wilson relation as measures of chirality.
Many-body formalism for fermions: Enforcing the Pauli principle on paper
NASA Astrophysics Data System (ADS)
Watson, D. K.
2015-07-01
Confined quantum systems involving N identical interacting fermions are found in many areas of physics, including condensed matter, atomic, nuclear, and chemical physics. In a previous series of papers, a many-body perturbation method that is applicable to both weakly and strongly interacting systems of bosons has been set forth by the author and coworkers. A symmetry-invariant perturbation theory was developed that uses group theory coupled with the dimension of space as the perturbation parameter to obtain an analytic correlated wave function through first order for a system under spherical confinement with a general two-body interaction. In the present paper, we extend this formalism to large systems of fermions, circumventing the numerical demands of applying the Pauli principle by enforcing the Pauli principle on paper. The method does not scale in complexity with N and has minimal numerical cost. We apply the method to a unitary Fermi gas and compare to recent Monte Carlo values.
Real-time evolution of strongly coupled fermions driven by dissipation
NASA Astrophysics Data System (ADS)
Huffman, E.; Banerjee, D.; Chandrasekharan, S.; Wiese, U.-J.
2016-09-01
We consider the real-time evolution of a strongly coupled system of lattice fermions whose dynamics is driven entirely by dissipative Lindblad processes, with linear or quadratic quantum jump operators. The fermion 2-point functions obey a closed set of differential equations, which can be solved with linear algebra methods. The staggered occupation order parameter of the t- V model decreases exponentially during the dissipative time evolution. The structure factor associated with the various Fourier modes shows the slowing down of low-momentum modes, which is due to particle number conservation. The processes with nearest-neighbor-dependent Lindblad operators have a decay rate that is proportional to the coordination number of the spatial lattice.
Observing fermionic statistics with photons in arbitrary processes
Matthews, Jonathan C. F.; Poulios, Konstantinos; Meinecke, Jasmin D. A.; Politi, Alberto; Peruzzo, Alberto; Ismail, Nur; Wörhoff, Kerstin; Thompson, Mark G.; O'Brien, Jeremy L.
2013-01-01
Quantum mechanics defines two classes of particles-bosons and fermions-whose exchange statistics fundamentally dictate quantum dynamics. Here we develop a scheme that uses entanglement to directly observe the correlated detection statistics of any number of fermions in any physical process. This approach relies on sending each of the entangled particles through identical copies of the process and by controlling a single phase parameter in the entangled state, the correlated detection statistics can be continuously tuned between bosonic and fermionic statistics. We implement this scheme via two entangled photons shared across the polarisation modes of a single photonic chip to directly mimic the fermion, boson and intermediate behaviour of two-particles undergoing a continuous time quantum walk. The ability to simulate fermions with photons is likely to have applications for verifying boson scattering and for observing particle correlations in analogue simulation using any physical platform that can prepare the entangled state prescribed here. PMID:23531788
Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals.
Bradlyn, Barry; Cano, Jennifer; Wang, Zhijun; Vergniory, M G; Felser, C; Cava, R J; Bernevig, B Andrei
2016-08-01
In quantum field theory, we learn that fermions come in three varieties: Majorana, Weyl, and Dirac. Here, we show that in solid-state systems this classification is incomplete, and we find several additional types of crystal symmetry-protected free fermionic excitations. We exhaustively classify linear and quadratic three-, six-, and eight-band crossings stabilized by space group symmetries in solid-state systems with spin-orbit coupling and time-reversal symmetry. Several distinct types of fermions arise, differentiated by their degeneracies at and along high-symmetry points, lines, and surfaces. Some notable consequences of these fermions are the presence of Fermi arcs in non-Weyl systems and the existence of Dirac lines. Ab initio calculations identify a number of materials that realize these exotic fermions close to the Fermi level. PMID:27445310
Fermion tunneling from higher-dimensional black holes
Lin Kai; Yang Shuzheng
2009-03-15
Via the semiclassical approximation method, we study the 1/2-spin fermion tunneling from a higher-dimensional black hole. In our work, the Dirac equations are transformed into a simple form, and then we simplify the fermion tunneling research to the study of the Hamilton-Jacobi equation in curved space-time. Finally, we get the fermion tunneling rates and the Hawking temperatures at the event horizon of higher-dimensional black holes. We study fermion tunneling of a higher-dimensional Schwarzschild black hole and a higher-dimensional spherically symmetric quintessence black hole. In fact, this method is also applicable to the study of fermion tunneling from four-dimensional or lower-dimensional black holes, and we will take the rainbow-Finsler black hole as an example in order to make the fact explicit.
Fermion tunneling from higher-dimensional black holes
NASA Astrophysics Data System (ADS)
Lin, Kai; Yang, Shu-Zheng
2009-03-01
Via the semiclassical approximation method, we study the 1/2-spin fermion tunneling from a higher-dimensional black hole. In our work, the Dirac equations are transformed into a simple form, and then we simplify the fermion tunneling research to the study of the Hamilton-Jacobi equation in curved space-time. Finally, we get the fermion tunneling rates and the Hawking temperatures at the event horizon of higher-dimensional black holes. We study fermion tunneling of a higher-dimensional Schwarzschild black hole and a higher-dimensional spherically symmetric quintessence black hole. In fact, this method is also applicable to the study of fermion tunneling from four-dimensional or lower-dimensional black holes, and we will take the rainbow-Finsler black hole as an example in order to make the fact explicit.
New Fermionic Soft Theorems for Supergravity Amplitudes.
Chen, Wei-Ming; Huang, Yu-Tin; Wen, Congkao
2015-07-10
Soft limits of a massless S matrix are known to reflect the symmetries of the theory. In particular, for theories with Goldstone bosons, the double-soft limit of scalars reveals the coset structure of the vacuum manifold. In this Letter, we propose that such universal double-soft behavior is not only true for scalars, but also for spin-1/2 particles in four dimensions and fermions in three dimensions. We first consider the Akulov-Volkov theory and demonstrate that the double-soft limit of Goldstinos yields the supersymmetry algebra. More surprisingly, we also find that amplitudes in 4≤N≤8 supergravity theories in four dimensions as well as N=16 supergravity in three dimensions behave universally in the double-soft-fermion limit, analogous to the scalar ones. The validity of the new soft theorems at loop level is also studied. The results for supergravity are beyond what is implied by supersymmetry Ward identities and may impose nontrivial constraints on the possible counterterms for supergravity theories. PMID:26207460
Quantum phases of AB 2 fermionic chains
NASA Astrophysics Data System (ADS)
Murcia-Correa, L. S.; Franco, R.; Silva-Valencia, J.
2016-02-01
A fermionic chain is a one-dimensional system with fermions that interact locally and can jump between sites in the lattice, in particular an AB n chain type, where A and B are sites that exhibit a difference in energy level of Δ and site B is repeated n-times, such that the unit cell has n +1 sites. A limit case of this model, called the ionic Hubbard model (n = 1), has been widely studied due to its interesting physics and applications. In this paper, we study the ground state of an AB 2 chain, which describes the material R 4[Pt 2(P 2O5H2)4X] · nH 2 O. Specifically, we consider a filling with two electrons per unit cell, and using the density matrix renormalization group method we found that the system exhibits the band insulator and Mott correlated insulator phases, as well as an intermediate phase between them. For couplings of Δ = 2,10 and 20, we estimate the critical points that separate these phases through the structure factor and the energy gap in the sector of charge and spin, finding that the position of the critical point rises as a function of Δ.
Perturbative Corrections for Staggered Fermion Bilinears
Patel, Apoorva; Sharpe, Stephen
1992-01-01
We calculate the perturbative corrections to fermion bilinears that are used in numerical simulations when extracting weak matric elements using staggered fermions.This extends previous calculations of Golterman and Smit, and Daniel and Sheard.In particular, we calculate the corrections for non-local bilinears defined in Landau gauge with gauge links excluded.We do this for the simplest operators, i.e. those defined on a 2^4 hypercube, and for tree level improved operators which live on 4^4 hypercubes.We also consider gauge invariant operators in which the "tadpole" contributions are suppressed by projecting the sums of products of gauge links back in to the gauge group.In all cases, we find that the variation in the size of the perturbative corrections is smaller than those with the gauge invariant unimproved operators.This is most strikingly true for the smeared operators.We investigate the efficacy of the mean-field method of Lepage and Mackenzie at summing up tadpole
Search for Majorana fermions in topological superconductors.
Pan, Wei; Shi, Xiaoyan; Hawkins, Samuel D.; Klem, John Frederick
2014-10-01
The goal of this project is to search for Majorana fermions (a new quantum particle) in a topological superconductor (a new quantum matter achieved in a topological insulator proximitized by an s-wave superconductor). Majorana fermions (MFs) are electron-like particles that are their own anti-particles. MFs are shown to obey non-Abelian statistics and, thus, can be harnessed to make a fault-resistant topological quantum computer. With the arrival of topological insulators, novel schemes to create MFs have been proposed in hybrid systems by combining a topological insulator with a conventional superconductor. In this LDRD project, we will follow the theoretical proposals to search for MFs in one-dimensional (1D) topological superconductors. 1D topological superconductor will be created inside of a quantum point contact (with the metal pinch-off gates made of conventional s-wave superconductors such as niobium) in a two-dimensional topological insulator (such as inverted type-II InAs/GaSb heterostructure).
Technology Transfer Automated Retrieval System (TEKTRAN)
On July 29-31, 2014, the US Environmental Protection Agency convened a public meeting of the FIFRA Scientific Advisory Panel (SAP) to address scientific issues associated with the agency’s “new High Throughput Methods to Estimate Chemical Exposure”. EPA is proposing to use these methods to identify...
Technology Transfer Automated Retrieval System (TEKTRAN)
On September 15-17th, 2014, the US Environmental Protection Agency convened a public meeting of the FIFRA Scientific Advisory Panel (SAP) to address scientific issues associated with the agency’s “Development of a Spatial Aquatic Model (SAM) for Pesticide Risk Assessment”. The goal of SAM is to impr...
ERIC Educational Resources Information Center
Pieper, Gail W.
1980-01-01
Describes how scientific documentation is taught in three 50-minute sessions in a technical writing course. Tells how session one distinguishes between in-text notes, footnotes, and reference entries; session two discusses the author-year system of citing references; and session three is concerned with the author-number system of reference…
ERIC Educational Resources Information Center
National Science Teachers Association (NJ1), 2004
2004-01-01
Scientific inquiry reflects how scientists come to understand the natural world, and it is at the heart of how students learn. From a very early age, children interact with their environment, ask questions, and seek ways to answer those questions. Understanding science content is significantly enhanced when ideas are anchored to inquiry…
Kraft, Giuliano
2002-01-01
To give a correct and effective scientific presentation, is an arduous task that asks for close examination of basic techniques of communication. This article proposes indications and suggestions to help public speakers to be communicators, to use visual aids and it explains how to capture the audience attention. PMID:12599721
Scientific and Technical Document Database
National Institute of Standards and Technology Data Gateway
NIST Scientific and Technical Document Database (PC database for purchase) The images in NIST Special Database 20 contain a very rich set of graphic elements from scientific and technical documents, such as graphs, tables, equations, two column text, maps, pictures, footnotes, annotations, and arrays of such elements.
Nonequilibrium steady states of ideal bosonic and fermionic quantum gases
NASA Astrophysics Data System (ADS)
Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André
2015-12-01
We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.
Fermion masses in the economical 3-3-1 model
Dong, P. V.; Huong, Tr. T.; Huong, D. T.; Long, H. N.
2006-09-01
We show that, in frameworks of the economical 3-3-1 model, all fermions get masses. At the tree level, one up-quark and two down-quarks are massless, but the one-loop corrections give all quarks the consistent masses. This conclusion is in contradiction to the previous analysis in which the third scalar triplet has been introduced. This result is based on the key properties of the model: First, there are three quite different scales of vacuum expectation values: {omega}{approx}O(1) TeV, v{approx_equal}246 GeV, and u{approx}O(1) GeV. Second, there exist two types of Yukawa couplings with different strengths: the lepton-number conserving couplings h's and the lepton-number violating ones s's satisfying the condition in which the second are much smaller than the first ones: s<
Nonequilibrium steady states of ideal bosonic and fermionic quantum gases.
Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André
2015-12-01
We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013)]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state. PMID:26764644
NASA Astrophysics Data System (ADS)
Gu, Zheng-Cheng; Wen, Xiao-Gang
2014-09-01
Symmetry-protected topological (SPT) phases are gapped short-range-entangled quantum phases with a symmetry G, which can all be smoothly connected to the trivial product states if we break the symmetry. It has been shown that a large class of interacting bosonic SPT phases can be systematically described by group cohomology theory. In this paper, we introduce a (special) group supercohomology theory which is a generalization of the standard group cohomology theory. We show that a large class of short-range interacting fermionic SPT phases can be described by the group supercohomology theory. Using the data of supercocycles, we can obtain the ideal ground state wave function for the corresponding fermionic SPT phase. We can also obtain the bulk Hamiltonian that realizes the SPT phase, as well as the anomalous (i.e., non-onsite) symmetry for the boundary effective Hamiltonian. The anomalous symmetry on the boundary implies that the symmetric boundary must be gapless for (1+1)-dimensional [(1+1)D] boundary, and must be gapless or topologically ordered beyond (1+1)D. As an application of this general result, we construct a new SPT phase in three dimensions, for interacting fermionic superconductors with coplanar spin order (which have T2=1 time-reversal Z2T and fermion-number-parity Z2f symmetries described by a full symmetry group Z2T×Z2f). Such a fermionic SPT state can neither be realized by free fermions nor by interacting bosons (formed by fermion pairs), and thus are not included in the K-theory classification for free fermions or group cohomology description for interacting bosons. We also construct three interacting fermionic SPT phases in two dimensions (2D) with a full symmetry group Z2×Z2f. Those 2D fermionic SPT phases all have central-charge c =1 gapless edge excitations, if the symmetry is not broken.
Scientific Claims versus Scientific Knowledge.
ERIC Educational Resources Information Center
Ramsey, John
1991-01-01
Provides activities that help students to understand the importance of the scientific method. The activities include the science of fusion and cold fusion; a group activity that analyzes and interprets the events surrounding cold fusion; and an application research project concerning a current science issue. (ZWH)
NASA Astrophysics Data System (ADS)
Moore, John W.
2002-12-01
These cases provide a good basis for discussions of scientific ethics, particularly with respect to the responsibilities of colleagues in collaborative projects. With increasing numbers of students working in cooperative or collaborative groups, there may be opportunities for more than just discussion—similar issues of responsibility apply to the members of such groups. Further, this is an area where, “no clear, widely accepted standards of behavior exist” (1). Thus there is an opportunity to point out to students that scientific ethics, like science itself, is incomplete and needs constant attention to issues that result from new paradigms such as collaborative research. Finally, each of us can resolve to pay more attention to the contributions we and our colleagues make to collaborative projects, applying to our own work no less critical an eye than we would cast on the work of those we don’t know at all.
(Strongly interacting fermion systems: Emphasis on heavy fermions: Annual performance report)
Not Available
1987-01-01
The research has been concentrated into two areas: heavy fermions and development of new methods for electronic properties (henceforth referred to as the ''electronic structure program''). This first area is going into deep hibernation due to the new interest in the high-T/sub c/ materials; notwithstanding this development, there has been significant progress. On the other hand, in the electronic structure program there has been a period of intense development which is just starting to yield results.
SU(8) Family Unification with Boson Fermion Balance
NASA Astrophysics Data System (ADS)
Adler, Stephen L.
2015-03-01
We formulate an SU(8) family unification model motivated by requiring that the theory should incorporate the graviton, gravitinos, and the fermions and gauge fields of the standard model, with boson.fermion balance. Gauge field SU(8) anomalies cancel between the gravitinos and spin 1/2 fermions. The 56 of scalars breaks SU(8) to SU(3)family×SU(5)×U(1)/Z5, with the fermion representation content needed for "flipped" SU(5) with three families, and with residual scalars in the 10 and overline {10} representations that break flipped SU(5) to the standard model. Dynamical symmetry breaking can account for the generation of 5 representation scalars needed to break the electroweak group. Yukawa couplings of the 56 scalars to the fermions are forbidden by chiral and gauge symmetries, so in the first stage of SU(8) breaking fermions remain massless. In the limit of vanishing gauge coupling, there are N = 1 and N = 8 supersymmetries relating the scalars to the fermions, which restrict the form of scalar self-couplings and should improve the convergence of perturbation theory, if not making the theory finite and "calculable." In an Appendix we give an analysis of symmetry breaking by a Higgs component, such as the (1, 1)(-15) of the SU(8) 56 under SU(8) ⊃ SU(3) × SU(5) × U(1), which has nonzero U(1) generator.
Dynamical fermion mass generation and exciton spectra in graphene
Zhang Chunxu; Liu Guozhu; Huang Mingqiu
2011-03-15
The Coulomb interaction between massless Dirac fermions may induce dynamical chiral symmetry breaking by forming excitonic pairs in clean graphene, leading to semimetal-insulator transition. If the Dirac fermions have zero bare mass, an exact continuous chiral symmetry is dynamically broken and thus there are massless Goldstone excitons. If the Dirac fermions have a small bare mass, an approximate continuous chiral symmetry is dynamically broken and the resultant Goldstone-type excitons become massive, which is analogous to what happens in QCD. In this paper, after solving the Dyson-Schwinger gap equation in the presence of a small bare fermion mass, we found a remarkable reduction of the critical Coulomb interaction strength for excitonic pair formation and a strong enhancement of dynamical fermion mass. We then calculate the masses of Goldstone-type excitons using the Shifman-Vainshtein-Zakharov sum-rule method and operator product expansion technique developed in QCD and find that the exciton masses are much larger than bare fermion mass but smaller than the width of dynamical fermion mass gap. We also study the spin susceptibilities and estimate the masses of non-Goldstone-type excitons using the same tools.
Polarization of massive fermions in a vortical fluid
NASA Astrophysics Data System (ADS)
Fang, Ren-hong; Pang, Long-gang; Wang, Qun; Wang, Xin-nian
2016-08-01
Fermions become polarized in a vortical fluid due to spin-vorticity coupling. Such a polarization can be calculated from the Wigner function in a quantum kinetic approach. By extending previous results for chiral fermions, we derive the Wigner function for massive fermions up to next-to-leading order in spatial gradient expansion. The polarization density of fermions can be calculated from the axial vector component of the Wigner function and is found to be proportional to the local vorticity ω . The polarizations per particle for fermions and antifermions decrease with the chemical potential and increase with energy (mass). Both quantities approach the asymptotic value ℏ ω /4 in the large energy (mass) limit. The polarization per particle for fermions is always smaller than that for antifermions, whose ratio of fermions to antifermions also decreases with the chemical potential. The polarization per particle on the Cooper-Frye freeze-out hypersurface can also be formulated and is consistent with the previous result of Becattini et al.
Composite fermions and broken symmetries in graphene.
Amet, F; Bestwick, A J; Williams, J R; Balicas, L; Watanabe, K; Taniguchi, T; Goldhaber-Gordon, D
2015-01-01
The electronic properties of graphene are described by a Dirac Hamiltonian with a four-fold symmetry of spin and valley. This symmetry may yield novel fractional quantum Hall (FQH) states at high magnetic field depending on the relative strength of symmetry-breaking interactions. However, observing such states in transport remains challenging in graphene, as they are easily destroyed by disorder. In this work, we observe in the first two Landau levels the two-flux composite-fermion sequences of FQH states between each integer filling factor. In particular, the odd-numerator fractions appear between filling factors 1 and 2, suggesting a broken-valley symmetry, consistent with our observation of a gap at charge neutrality and zero field. Contrary to our expectations, the evolution of gaps in a parallel magnetic field suggests that states in the first Landau level are not spin-polarized even up to very large out-of-plane fields. PMID:25562690
Composite fermions and broken symmetries in graphene
NASA Astrophysics Data System (ADS)
Amet, F.; Bestwick, A. J.; Williams, J. R.; Balicas, L.; Watanabe, K.; Taniguchi, T.; Goldhaber-Gordon, D.
2015-01-01
The electronic properties of graphene are described by a Dirac Hamiltonian with a four-fold symmetry of spin and valley. This symmetry may yield novel fractional quantum Hall (FQH) states at high magnetic field depending on the relative strength of symmetry-breaking interactions. However, observing such states in transport remains challenging in graphene, as they are easily destroyed by disorder. In this work, we observe in the first two Landau levels the two-flux composite-fermion sequences of FQH states between each integer filling factor. In particular, the odd-numerator fractions appear between filling factors 1 and 2, suggesting a broken-valley symmetry, consistent with our observation of a gap at charge neutrality and zero field. Contrary to our expectations, the evolution of gaps in a parallel magnetic field suggests that states in the first Landau level are not spin-polarized even up to very large out-of-plane fields.
Phenomenology with Wilson fermions using smeared sources
Patel, Apoorva; Daniel, D.; Kilcup, Gregory; Gupta, Rajan; Sharpe, Stephen
1992-01-01
We investigate the use of two types of non-local ("smeared") sources for quark propagators in quenched lattice QCD at beta=6.0 using Wilson fermions at k=0.154 and 0.155. We present results for the hadron mass spectrum, meson decay constants, quark masses, the chiral condensate and the quark distribution amplitude of the pion. The use of smeared sources leads to a considerable improvement over previous results. We find a disturbing discrepancy between the baryon spectra obtained using Wuppertal and wall sources. We find good signals in the ratio of correlators used to calculate the quark mass and the chiral condensate and show that the extrapolation to the chiral limit is smooth.
Tomography of Majorana fermions with STM tips
NASA Astrophysics Data System (ADS)
Chevallier, Denis; Klinovaja, Jelena
2016-07-01
We investigate numerically the possibility to detect the spatial profile of Majorana fermions (MFs) by using STM tips that are made of either normal or superconducting material. In both cases, we are able to resolve the localization length and the oscillation period of the MF wave function. We show that the tunneling between the substrate and the tip, necessary to get the information on the wave-function oscillations, has to be weaker in the case of a superconducting probe. In the strong tunneling regime, the differential conductance saturates making it more difficult to observe the exponential decay of MFs. The temperature broadening of the profile is strongly suppressed in the case of the superconducting tip resulting, generally, in better resolution.