Results 81 to 90 of about 47,027 (304)

Effective action and semiclassical limit of spin foam models

, 2011
We define an effective action for spin foam models of quantum gravity by adapting the background field method from quantum field theory. We show that the Regge action is the leading term in the semi-classical expansion of the spin foam effective action ...
A Miković, Abbot L, Baez J C, Barrett J W, Barrett J W, Barrett J W Dowdall R J Fairbairn W J Hellmann F Pereira R, Bianchi E, Fairbairn W Meusburger C, Freidel L, M Vojinović, Magliaro E, Makela J, Miković A, Miković A, Miković A, Miković A Vojinović M, Miković A Vojinović M   +16 more
core   +1 more source

Tunable Coordination Number in Non‐Metal‐Introduced Copper Catalysts Enables High‐Performance Electrochemical CO2 Reduction to C2 Products

Advanced Functional Materials, EarlyView.
Copper catalysts introduced with different non‐metallic elements regulating the coordination number of Cu are prepared by magnetron sputtering. Reducing the Cu coordination number enhances C─C coupling and boosts C2+ product selectivity, by lowering the energy barrier for the *CO → *CHO conversion step. The optimized Si‐doped Cu catalyst achieves a C2+
Xiaoye Du, Bo Gao, Yixuan Yang, Young In Jo, Dan Qian, Chunhui Xiao, Shujiang Ding, Zhongxiao Song, Ki Tae Nam   +8 more
wiley   +1 more source

Loop quantum cosmology and spin foams

Physics Letters B, 2009
Loop quantum cosmology (LQC) is used to provide concrete evidence in support of the general paradigm underlying spin foam models (SFMs). Specifically, it is shown that: i) the physical inner product in the timeless framework equals the transition amplitude in the deparameterized theory; ii) this quantity admits a %convergent vertex expansion a la SFMs ...
Miguel Campiglia, Abhay Ashtekar, Adam Henderson   +2 more
openaire   +3 more sources

Design and Applications of Multi‐Frequency Programmable Metamaterials for Adaptive Stealth

Advanced Functional Materials, EarlyView.
This article provides a comprehensive overview of metamaterials, including their fundamental principles, properties, synthesis techniques, and applications in stealth, as well as their challenges and future prospects. It covers topics that are more advanced than those typically discussed in existing review articles, while still being closely connected ...
Jonathan Tersur Orasugh, Ankita Mohanty, Amit Malakar, Suryasarathi Bose, Suprakas Sinha Ray   +4 more
wiley   +1 more source

Holonomy Spin Foam Models: Definition and Coarse Graining

, 2012
We propose a new holonomy formulation for spin foams, which naturally extends the theory space of lattice gauge theories. This allows current spin foam models to be defined on arbitrary two-complexes as well as to generalize current spin foam models to ...
Bahr, Benjamin, Dittrich, Bianca, Hellmann, Frank, Kaminski, Wojciech   +3 more
core   +1 more source

Device Integration Technology for Practical Flexible Electronics Systems

Advanced Functional Materials, EarlyView.
Flexible device integration technologies are essential for realizing practical flexible electronic systems. In this review paper, wiring and bonding techniques critical for the industrial‐scale manufacturing of wearable devices are emphasized based on flexible electronics.
Masahito Takakuwa, Kento Yamagishi, Sunghoon Lee, Yusaku Tagawa, Takao Someya, Tomoyuki Yokota   +5 more
wiley   +1 more source

Finiteness and Dual Variables for Lorentzian Spin Foam Models

, 2005
We describe here some new results concerning the Lorentzian Barrett-Crane model, a well-known spin foam formulation of quantum gravity. Generalizing an existing finiteness result, we provide a concise proof of finiteness of the partition function ...
Apostol T M, Ashtekar A, Baez J C, Baez J C, Baez J C, Baez J C, Barrett J W, Barrett J W, Barrett J W, Barrett J W, Barrett J W, Bojowald M Perez A, Borwein J, Cherrington J W, Cherrington J W Christensen J D, Christensen J D, Christensen J D, Crane L Perez A Rovelli C, Freidel L, J Wade Cherrington, Makela J, Makela J, Perez A, Pfeiffer H, Wainwright C   +24 more
core   +1 more source

Spin foam models and the classical action principle [PDF]

Advances in Theoretical and Mathematical Physics, 1998
We propose a new systematic approach that allows one to derive the spin foam (state sum) model of a theory starting from the corresponding classical action functional. It can be applied to any theory whose action can be written as that of the BF theory plus a functional of the B field.
Laurent Freidel, Kirill Krasnov
openaire   +3 more sources

Tailoring the Properties of Functional Materials With N‐Oxides

Advanced Functional Materials, EarlyView.
The properties of materials bearing N‐oxide groups are often dominated by the polar N+─O− bond. It provides hydrophilicity, selective ion‐binding, electric conductivity, or antifouling properties. Many of the underlying mechanisms have only recently been discovered, and the interest in N‐oxide materials is rapidly growing.
Timo Friedrich, Michelle Kobus, Shirin Mesgarha, Erica Moretto, Laurens Grosche, Wolfgang Maison   +5 more
wiley   +1 more source

Strategic Design of Oxophilic Dopants for Active and Durable Alkaline Hydrogen Evolution Reaction Under Seawater

Advanced Functional Materials, EarlyView.
This study explores a cost‐effective alternative by incorporating oxophilic dopants into non‐precious metal hosts to enhance water dissociation and catalyst stability. Computational screening identified Ni─V, Ni─Mo, and Co─V as top candidates. Subsequent experiments confirmed Ni20V exhibits superior HER activity, achieving 76 mV lower overpotential ...
Hyeonjung Jung, Yechan Lee, Kyuri Cho, Tae Yong Kim, Jihyeon Song, Han Sol Jung, Sung Il Park, Yoojin Lee, Jinuk Moon, Wongyu Park, Jaewoo Nam, Sangmin Park, Wooyul Kim, Jeong Woo Han   +13 more
wiley   +1 more source