Scattering amplitudes for all masses and spins Arkani-Hamed, Nima; Huang, Tzu-Chen; Huang, Yu-tin
The journal of high energy physics,
11/2021, Letnik:
2021, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
We introduce a formalism for describing four-dimensional scattering amplitudes for particles of any mass and spin. This naturally extends the familiar spinor-helicity formalism for massless ...particles to one where these variables carry an extra
SU
(2) little group index for massive particles, with the amplitudes for spin
S
particles transforming as symmetric rank 2
S
tensors. We systematically characterise all possible three particle amplitudes compatible with Poincare symmetry. Unitarity, in the form of consistent factorization, imposes algebraic conditions that can be used to construct all possible four-particle tree amplitudes. This also gives us a convenient basis in which to expand all possible four-particle amplitudes in terms of what can be called “spinning polynomials”. Many general results of quantum field theory follow the analysis of four-particle scattering, ranging from the set of all possible consistent theories for massless particles, to spin-statistics, and the Weinberg-Witten theorem. We also find a transparent understanding for why massive particles of sufficiently high spin cannot be “elementary”. The Higgs and Super-Higgs mechanisms are naturally discovered as an infrared unification of many disparate helicity amplitudes into a smaller number of massive amplitudes, with a simple understanding for why this can’t be extended to Higgsing for gravitons. We illustrate a number of applications of the formalism at one-loop, giving few-line computations of the electron (
g −
2) as well as the beta function and rational terms in QCD. “Off-shell” observables like correlation functions and form-factors can be thought of as scattering amplitudes with external “probe” particles of general mass and spin, so all these objects — amplitudes, form factors and correlators, can be studied from a common on-shell perspective.
Influenza infection is a cause of exacerbations in patients with chronic pulmonary diseases. The aim of this study was to investigate the clinical outcomes and identify risk factors associated with ...hospitalization and mortality following influenza infection in adult patients with bronchiectasis. Using the Chang Gung Research Database, we identified patients with bronchiectasis and influenza-related infection (ICD-9-CM 487 and anti-viral medicine) between 2008 and 2017. The main outcomes were influenza-related hospitalization and in-hospital mortality rate. Eight hundred sixty-five patients with bronchiectasis and influenza infection were identified. Five hundred thirty-six (62%) patients with bronchiectasis were hospitalized for influenza-related infection and 118 (22%) patients had respiratory failure. Compared to the group only seen in clinic, the hospitalization group was older, with more male patients, a lower FEV
higher bronchiectasis aetiology comorbidity index (BACI), and more acute exacerbations in the previous year. Co-infections were evident in 55.6% of hospitalized patients, mainly caused by
(15%), fungus (7%), and
(6%). The respiratory failure group developed acute kidney injury (36% vs. 16%;
< 0.001), and shock (47% vs. 6%;
< 0.001) more often than influenza patients without respiratory failure. The overall mortality rate was 10.8% and the respiratory failure group exhibited significantly higher in-hospital mortality rates (27.1% vs. 6.2%;
< 0.001). Age, BACI, and previous exacerbations were independently associated with influenza-related hospitalization. Age, presence of shock, and low platelet counts were associated with increased hospital mortality. Influenza virus caused severe exacerbation in bronchiectasis, especially in those who were older and who had high BACI scores and previous exacerbations. A high risk of respiratory failure and mortality were observed in influenza-related hospitalization in bronchiectasis. We highlight the importance of preventing or treating influenza infection in bronchiectasis.
Electronic structure greatly determines the band structures and the charge carrier transport properties of semiconducting photocatalysts and consequently their photocatalytic activities. Here, by ...simply calcining the mixture of graphitic carbon nitride (g‐C3N4) and sodium borohydride in an inert atmosphere, boron dopants and nitrogen defects are simultaneously introduced into g‐C3N4. The resultant boron‐doped and nitrogen‐deficient g‐C3N4 exhibits excellent activity for photocatalytic oxygen evolution, with highest oxygen evolution rate reaching 561.2 µmol h−1 g−1, much higher than previously reported g‐C3N4. It is well evidenced that with conduction and valence band positions substantially and continuously tuned by the simultaneous introduction of boron dopants and nitrogen defects into g‐C3N4, the band structures are exceptionally modulated for both effective optical absorption in visible light and much increased driving force for water oxidation. Moreover, the engineered electronic structure creates abundant unsaturated sites and induces strong interlayer C–N interaction, leading to efficient electron excitation and accelerated charge transport. In the present work, a facile approach is successfully demonstrated to engineer the electronic structures and the band structures of g‐C3N4 with simultaneous introduction of dopants and defects for high‐performance photocatalytic oxygen evolution, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.
Boron dopants and nitrogen defects are simultaneously introduced into g‐C3N4 through a simple NaBH4 thermal treatment approach. With exceptionally modulated band structures for effective optical absorption and increased water‐oxidation driving force, as well as engineered electronic structure for efficient electron excitation and facilitated charge transport, the resultant boron‐doped and nitrogen‐deficient g‐C3N4 exhibits excellent activity for photocatalytic oxygen evolution.
The unique applications of porous metal–organic framework (MOF) liquids with permanent porosity and fluidity have attracted significant attention. However, fabrication of porous MOF liquids remains ...challenging because of the easy intermolecular self‐filling of the cavity or the rapid settlement of porous hosts in hindered solvents that cannot enter their pores. Herein, we report a facile strategy for the fabrication of a MOF liquid (Im‐UiO‐PL) by surface ionization of an imidazolium‐functionalized framework with a sterically hindered poly(ethylene glycol) sulfonate (PEGS) canopy. The Im‐UiO‐PL obtained in this way has a CO2 adsorption approximately 14 times larger than that of pure PEGS. Distinct from a porous MOF solid counterpart, the stored CO2 in Im‐UiO‐PL can be slowly released and efficiently utilized to synthesize cyclic carbonates in the atmosphere. This is the first example of the use of a porous MOF liquid as a CO2 storage material for catalysis. It offers a new method for the fabrication of unique porous liquid MOFs with functional behaviors in various fields of gas adsorption and catalysis.
An ionization strategy has been developed to fabricate a porous MOF liquid, which shows large adsorption of CO2. The adsorbed CO2 can subsequently be slowly released and efficiently utilized to synthesize, for example, cyclic carbonates.
Bronchiectasis is a chronic infectious respiratory disease with diverse causes and ethnic or geographic differences. However, few large-scale studies of its etiology have been conducted in Asia. This ...study aimed to determine the etiology and clinical features of bronchiectasis in Taiwan.
This longitudinal cohort study investigated the etiology and clinical features of newly diagnosed non-cystic fibrosis bronchiectasis patients from January 2002 to December 2016. The clinical, functional and microbiological data of patients were retrieved from the Chang Gung Research Database, which includes seven medical facilities throughout Taiwan. The index date was the date of the first bronchiectasis diagnosis. Known diseases that were diagnosed before the index date were regarded as etiologies of bronchiectasis.
The cohort comprised 15,729 adult patients with bronchiectasis. Idiopathic (32%) was the most common cause, followed by post-pneumonia (24%). Other causes included post-tuberculosis (12%), chronic obstructive pulmonary disease (14%), asthma (10%), gastroesophageal reflux disease (2%) and rheumatic diseases (2%). At diagnosis, 8487 patients had sputum culture. Pseudomonas aeruginosa (5.3%) was the most common bacteria, followed by non-tuberculosis mycobacteria (3.6%), Haemophilus influenzae (3.4%) and Klebsiella pneumoniae (3.1%), but 6155 (72.1%) had negative sputum cultures. Patients with post-tuberculosis had a higher sputum isolation rate of non-tuberculosis mycobacteria than P. aeruginosa. Patients with post-tuberculosis and post-pneumonia bronchiectasis had a higher frequency of chronic lung infection than other groups (p < 0.05). Clinical characteristics, such as gender, lung function, comorbidities and microbiology, were significantly different between idiopathic and known etiologies.
Idiopathic, post-infection and tuberculosis constitute major bronchiectasis etiologies in Taiwan. Clinical characteristics and sputum microbiology were distinct among separate etiology phenotypes.
The electrosynthesis from 5‐hydroxymethylfurfural (HMF) is considered a green strategy to achieve biomass‐derived high‐value chemicals. As the molecular structure of HMF is relatively complicated, ...understanding the HMF adsorption/catalysis behavior on electrocatalysts is vital for biomass‐based electrosynthesis. The electrocatalysis behavior can be modulated by tuning the adsorption energy of the reactive molecules. In this work, the HMF adsorption behavior on spinel oxide, Co3O4 is discovered. Correspondingly, the adsorption energy of HMF on Co3O4 is successfully tuned by decorating with single‐atom Ir. It is observed that compared with bare Co3O4, single‐atom‐Ir‐loaded Co3O4 (Ir‐Co3O4) can enhance adsorption with the CC groups of HMF. The synergetic adsorption can enhance the overall conversion of HMF on electrocatalysts. With the modulated HMF adsorption, the as‐designed Ir‐Co3O4 exhibits a record performance (with an onset potential of 1.15 VRHE) for the electrosynthesis from HMF.
Single atoms of Ir are anchored on Co3O4 for efficient electro‐oxidation of 5‐hydroxymethylfurfural (HMF). It is found that an isolated Ir atom can optimize the adsorption configuration of HMF molecules on catalysts and accelerate HMF oxidation.
Landslides are natural phenomena that can cause great loss of life and damage to property. A landslide susceptibility map is a useful tool to help with land management in landslide-prone areas. A ...support vector machine (SVM) is a machine learning algorithm that uses a small number of samples for prediction and has been widely used in recent years. This paper presents a review of landslide susceptibility mapping using SVM. It presents the basic concept of SVM and its application in landslide susceptibility assessment and mapping. Then it compares the SVM method with four other methods (analytic hierarchy process, logistic regression, artificial neural networks and random forests) used in landslide susceptibility mapping. The application of SVM in landslide susceptibility assessment and mapping is discussed and suggestions for future research are presented. Compared with some of the methods commonly used in landslide susceptibility assessment and mapping, SVM has its strengths and weaknesses owing to its unique theoretical basis. The combination of SVM and other techniques may yield better performance in landslide susceptibility assessment and mapping. A high-quality informative database is essential and classification of landslide types prior to landslide susceptibility assessment is important to help improve model performance.
•Comparing different landslide susceptibility mapping models from various aspects•Reconsidering the assumptions used in building the model.•Proposing future works by SVM to assess landslide susceptibility.
Kerr black holes as elementary particles Arkani-Hamed, Nima; Huang, Yu-tin; O’Connell, Donal
The journal of high energy physics,
01/2020, Letnik:
2020, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A
bstract
Long ago, Newman and Janis showed that a complex deformation
z → z
+
ia
of the Schwarzschild solution produces the Kerr solution. The underlying explanation for this relationship has ...remained obscure. The complex deformation has an electromagnetic counterpart: by shifting the Coloumb potential, we obtain the EM field of a certain rotating charge distribution which we term
Kerr
. In this note, we identify the origin of this shift as arising from the exponentiation of spin operators for the recently defined “minimally coupled” three-particle amplitudes of spinning particles coupled to gravity, in the large- spin limit. We demonstrate this by studying the impulse imparted to a test particle in the background of the heavy spinning particle. We first consider the electromagnetic case, where the impulse due to
Kerr
is reproduced by a charged spinning particle; the shift of the Coloumb potential is matched to the exponentiated spin-factor appearing in the amplitude. The known impulse due to the Kerr black hole is then trivially derived from the gravitationally coupled spinning particle via the double copy.
Combining noble metals with nonnoble metals is an attractive strategy to balance the activity and cost of electrocatalysts. However, a guiding principle for selecting suitable nonnoble metals is ...still lacking. Herein, a thorough mechanistic study on the platform oxygen evolution reaction (OER) electrocatalyst of Ir@Co3O4 to deeply understand the synergy between Ir and Co3O4 for the boosted OER has been carried out. It is demonstrated that the pseudocapacitive feature of Co3O4 plays a key role in accumulating sufficient positive charge Q, while the Ir sites are responsible for achieving a high reaction order (β), synergistically contributing to the high OER activity of Ir@Co3O4 through the rate law equation. Specifically, Ir@Co3O4 displays a low overpotential of 280 mV at 10 mA cm−2 with a small Ir loading of 1.4 wt%. Ir@Co3O4 is further applied to Zn‐air batteries, which enables a low charging potential and thus alleviates the oxidative corrosion of the air electrode, leading to improved cycle stability of 210 h at 20 mA cm−2. This work demonstrates that anchoring active noble metal sites (for high β) on pseudocapacitive supports (for high Q) is highly favorable to the OER process, providing a clear guidance for boosting the utilization of noble metals in electrocatalysis.
Ultra‐low loading Ir (1.4 wt%) is anchored on Co3O4 for oxygen evolution reaction (OER). The pseudocapacitive Co3O4 helps accumulate the positive charge Q, while the Ir sites help achieve a high reaction order (β). Anchoring the ultra‐low loading noble catalyst on the pseudocapacitive non‐noble catalyst is a promising strategy for high‐performance low‐cost catalyst development.
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