Carrollian Yang-Mills theory Islam, Minhajul
The journal of high energy physics,
05/2023, Volume:
2023, Issue:
5
Journal Article
Peer reviewed
Open access
A
bstract
By doing a small
c
(speed of light) expansion of SU(
N
) Yang-Mills fields, we construct two different electric and two different magnetic sectors actions of Carrollian Yang-Mills theory. ...For both electric and magnetic cases, one sector contains non-trivial self-interaction, and another is
N
2
−
1 copies of respective sector Carrollian abelian theory. In
d
= 4, all the four sectors are invariant under infinite Carrollian Conformal symmetry. There are no central extensions when analyzing charge algebra at the phase space level. Lastly, we compute propagators for all four sectors and vertices for two non-trivial sectors. Propagators in position space show ultra-local behavior.
We explore the realization of BRST symmetry in the non-Lorentzian Yang-Mills Lagrangian within the context of Galilean and Carrollian Yang-Mills theory. Firstly, we demonstrate the nilpotent property ...of classical BRST transformations and construct corresponding conserve charges for both cases. Then, we analyze the algebra of these charges and observe the nilpotent properties at the algebraic level. The findings of this study contribute to an understanding of BRST symmetry in non-Lorentzian Yang-Mills Lagrangians and provide insights into the algebraic properties of related conserve charges.
•The configuration of ground state of UX2 (X = O, N, C, Si and S) solids is found by geometry optimization by applying DFT + U functional at zero pressure.•The calculated structural and electronic ...properties are agreed well with the other reported experimental and computational results.•Most of the elastic parameters specially the lattice thermal conductivity of UX2 compounds are computed by the famous Slack's equation for the first time.•The mechanical and thermal properties suggest that, UC2 and UN2 can be the potential alternatives to UO2 solid nuclear fuels.•Furthermore, this study contributes to the ongoing effort to identify alternative fuel materials for nuclear power reactors and lays the foundation for future research in this area.
This study investigates and compares the physical properties of various UX2 (X = O, N, C, Si and S) nuclear fuels using a combination of Density Functional Theory (DFT) and Hubbard U correction parameter (U) to accurately model the electronic structure and account for strong correlation effects among 5f orbital electrons. Spin-polarized DFT + U method is employed to optimize the structures of the considered compounds. The computational analysis reveals that UO2 and UN2 exhibit Mott-insulating properties, while the remaining UX2 compounds demonstrate metallic nature. To assess the mechanical aspects of these materials, the study evaluates their mechanical stability, Vickers hardness and machinability index through calculations of elastic constants. Notably, all the UX2 fuels are found to be mechanically stable and possess ductility. Both the two-dimensional (2D) and three-dimensional (3D) depictions of the elastic moduli for the analyzed solid fuels demonstrate the presence of elastic anisotropy. The famous Slack's equation is used to determine the lattice thermal conductivity of the UX2 fuels, providing valuable insights into their thermal properties. Among the investigated materials, UC2 exhibits the highest values of Debye temperature and lattice thermal conductivity, which amount to 412 K and 15.73 Wm−1 K−1 at 300 K, respectively. Furthermore, UN2 demonstrates the highest melting temperature. Among the compounds under investigation, UC2 and UN2 fuels exhibit the most minimal thermal expansion and the greatest heat capacity. Based on these findings, UC2 and UN2 emerge as promising alternative fuel materials to UO2 for potential use in nuclear power reactors. This research contributes to the ongoing efforts in identifying alternative fuel materials.
Display omitted
Magic fermions: Carroll and flat bands Bagchi, Arjun; Banerjee, Aritra; Basu, Rudranil ...
The journal of high energy physics,
03/2023, Volume:
2023, Issue:
3
Journal Article
Peer reviewed
Open access
A
bstract
The Carroll algebra is constructed as the
c →
0 limit of the Poincare algebra and is associated to symmetries on generic null surfaces. In this paper, we begin investigations of Carrollian ...fermions or fermions defined on generic null surfaces. Due to the availability of two different (degenerate) metrics on Carroll spacetimes, there is the possibility of two different versions of Carroll Clifford algebras. We consider both possibilities and construct explicit representations of Carrollian gamma matrices and show how to build higher spacetime dimensional representations out of lower ones. Actions for Carroll fermions are constructed with these gamma matrices and the properties of these actions are investigated.
We show that in condensed matter systems where the dispersion relation becomes trivial i.e. the energy is not dependent on momentum and bands flatten out, Carroll symmetry generically appears. We give explicit examples of this including that of twisted bi-layer graphene, where superconductivity appears at so called magic angles and connect this to Carroll fermions.
In recent years, there have been increasingly rapid advances of using bioactive materials in tissue engineering applications. Bioactive materials constitute many different structures based upon ...ceramic, metallic or polymeric materials, and can elicit specific tissue responses. However, most of them are relatively brittle, stiff, and difficult to form into complex shapes. Hence, there has been a growing demand for preparing materials with tailored physical, biological, and mechanical properties, as well as predictable degradation behavior. Chitosan-based materials have been shown to be ideal bioactive materials due to their outstanding properties such as formability into different structures, and fabricability with a wide range of bioactive materials, in addition to their biocompatibility and biodegradability. This review highlights scientific findings concerning the use of innovative chitosan-based bioactive materials in the fields of tissue engineering, with an outlook into their future applications. It also covers latest developments in terms of constituents, fabrication technologies, structural, and bioactive properties of these materials that may represent an effective solution for tissue engineering materials, making them a realistic clinical alternative in the near future.
Display omitted
•Chitosan based materials are potential candidates for tissue engineering.•Recent findings on chitosan based bioactive materials are summarized.•Applications in different fields of tissue engineering are discussed.•Limitations, challenges and future prospects are discussed.
Purpose
This study aims to investigate how entrepreneurial anxiety develops during the entrepreneurial intention stage in a developing country such as Bangladesh, where doing business has long been a ...challenge, and examine how individuals manage their entrepreneurial anxiety. Indeed, understanding how anxiety is formed when individuals decide to start a business has been a challenge, because such a decision is influenced by both individual and contextual factors.
Design/methodology/approach
This study applies thematic analysis to examine how individuals experience and react to entrepreneurial anxiety in a developing country context when they make a decision to start a business using data from 30 in-depth semistructured interviews with 20 aspiring and 10 active entrepreneurs. All participants are Bangladeshi nationals.
Findings
Consistent with earlier studies, the findings of this study revealed that entrepreneurial anxiety is regarded as a type of distress, doubt, fear, uneasiness and worry. Moreover, 11 distinct sources of entrepreneurial anxiety were identified, suggesting that some individuals develop problem-focused coping strategies to stay firm on their decision to start a business as planned, whereas others procrastinate.
Research limitations/implications
The findings add new dimensions to the theory of entrepreneurial anxiety and offer practical implications for aspiring entrepreneurs, policymakers, parents and society as a whole.
Originality/value
This study contributes to an underexplored area of emotion in entrepreneurship by conceptualizing how entrepreneurial anxiety develops during a specific stage of the entrepreneurial process, that is, entrepreneurial intention.
Purpose
Despite entrepreneurial intentions being a central and enduring construct in entrepreneurship research, most research on intentions focused on factors that underpin an individual's ...entrepreneurial intentions. This study extends the emerging literature on fear of failure and resilience to understand how they influence entrepreneurial intentions. The authors do this in a context where job prospects are low, and unemployment is high to understand what potentially prevents educated youth in a developing country from pursuing self-employment.
Design/methodology/approach
This study applies the structural equation modelling (SEM) using AMOS 25 to test the hypotheses on a sample of 238 third- and fourth-year Bangladeshi students facing an important career decision. A replication study is also conducted with an additional sample (n = 209) to verify the robustness of the findings, using a different measurement of resilience and a different analysis method – partial least square (PLS)-SEM in Smart-PLS 3.
Findings
The study finds support for the mediation model where fear of failure mediates the relationship between resilience and entrepreneurial intentions. The findings suggest that resilience enhances entrepreneurial intentions while also reducing the negative effects of fear of failure on entrepreneurial intentions.
Originality/value
This study contributes to an underexplored area of entrepreneurial intentions literature by exploring how resilience relates to fear of failure and entrepreneurial intentions. The findings demonstrate the importance of resilience through its direct effect on intentions as well as its indirect effect through its influence on fear of failure. The findings have implications for potential entrepreneurs and educational institutions providing training in entrepreneurship.
Galilean gauge theories from null reductions Bagchi, Arjun; Basu, Rudranil; Islam, Minhajul ...
The journal of high energy physics,
04/2022, Volume:
2022, Issue:
4
Journal Article
Peer reviewed
Open access
A
bstract
The procedure of null reduction provides a concrete way of constructing field theories with Galilean invariance. We use this to examine Galilean gauge theories, viz. Galilean ...electrodynamics and Yang-Mills theories in spacetime dimensions 3 and 4. Different non-relativistic conformal symmetries arise in these contexts: Schrödinger symmetry in
d
= 3 and Galilean conformal symmetry in
d
= 4. A canonical analysis further reveals that the symmetries enhance to their infinite dimensional versions in phase space and pick up central extensions. In addition, for the Abelian theory, we discuss non-relativistic electro- magnetic duality in
d
= 3 and its difference with the
d
= 4 version. We also mention some quantum aspects for both Abelian and non-Abelian theories.
Abstract Dehydrogenation chemistry has long been established as a fundamental aspect of organic synthesis, commonly encountered in carbonyl compounds. Transition metal catalysis revolutionized it, ...with strategies like transfer-dehydrogenation, single electron transfer and C–H activation. These approaches, extended to multiple dehydrogenations, can lead to aromatization. Dehydrogenative transformations of aliphatic carboxylic acids pose challenges, yet engineered ligands and metal catalysis can initiate dehydrogenation via C–H activation, though outcomes vary based on substrate structures. Herein, we have developed a catalytic system enabling cyclohexane carboxylic acids to undergo multifold C–H activation to furnish olefinated arenes, bypassing lactone formation. This showcases unique reactivity in aliphatic carboxylic acids, involving tandem dehydrogenation-olefination-decarboxylation-aromatization sequences, validated by control experiments and key intermediate isolation. For cyclopentane carboxylic acids, reluctant to aromatization, the catalytic system facilitates controlled dehydrogenation, providing difunctionalized cyclopentenes through tandem dehydrogenation-olefination-decarboxylation-allylic acyloxylation sequences. This transformation expands carboxylic acids into diverse molecular entities with wide applications, underscoring its importance.
Purpose
While compassionate and morally motivated people are theorised to be more likely to engage in activities that contribute to the social good, the literature provides contradictory evidence ...regarding the role of empathy and moral obligation in building social entrepreneurial intention (SEI). This study aims to clarify how empathy and moral obligation influence SEI.
Design/methodology/approach
The authors used survey data (n = 307) from Bangladesh, a frontier economy, to test the hypothesised relationships between empathy, moral obligation and SEI by applying partial least square–structural equation modelling in Smart PLS 3. They then conducted a second study with a larger sample (n = 339) from Saudi Arabia, an emerging economy, to further investigate how the findings withstand in a different socio-economic context.
Findings
The findings contradicted extant conceptualisations and revealed that empathy and moral obligation influence SEI indirectly through other individual and contextual factors, such as social entrepreneurial self-efficacy and perceived social support. The findings indicate that a person with a feeling of compassion and moral responsibility to help others will not start a social venture unless they feel capable and supported to start and run the venture.
Originality/value
The study contributes to a contentious area of research in SEI by demonstrating the links between various individual-level (empathy, moral obligation and social entrepreneurial self-efficacy) and contextual-level (perceived social support) variables and their relationship with SEI.
PDF
