Judul: Analysis of Investor Reactions to the Announcement of Right Issue At The Indonesian Stock Exchage Issuers Before And During The Covid-19 Pandemic
Abstrak: Pandemi COVID-19 berdampak terjadinya fluktuasi terhadap pergerakan harga saham, dan sangat mempengaruhi kondisi ekonomi begitupun reaksi investor terhadap kebijakan right issue yang akan mempengaruhi minat jual beli saham. Studi ini mengamati perkembangan aktivitas pasar di mana investor bereaksi terhadap informasi dengan mempertimbangkan sifat dinamis pasar modal melalui bullish dan bearish sebelum maupun selama pandemi COVID-19. Penelitian ini bertujuan untuk mengidentifikasi periode bullish dan bearish di Bursa Efek Indonesia periode 2017-2020, mengidentifikasi pengaruh COVID-19 terhadap aksi right issue, menganalisis perbedaan rata-rata excess return dan likuiditas saham yang diukur dengan bid-ask spread sebelum dan sesudah pengumuman right issue masa sebelum dan selama pandemi COVID-19, kemudian menganalisis pengaruh right issue pada dividen per share yang akan diterima oleh pemegang saham masa sebelum dan selama pandemi COVID-19, serta menguji apakah pasar modal Indonesia mengikuti the semi strong efficient market. Penelitian ini menggunakan 50 sampel perusahaan dari tahun 2017-2020, metode penarikan sampel menggunakan purposive sampling dan menggunakan event study dengan pendekatan market model, uji normalitasnya adalah Kolmogorov–smirnov, uji statistik menggunakan uji beda dua rata (wilcoxon signed rank test dan paired sample t- test), serta identifikasi bullish dan bearish menggunakan analisis candlestick. Secara umum IHSG menunjukkan pola bullish sebagai tren utama dengan persentase (64.58%) dan bearish (35.42%). Hasil penelitian menunjukkan bahwa terdapat perbedaan excess return yang signifikan sebelum dan sesudah pengumuman rights issue pada periode sebelum COVID-19 namun tidak terdapat perbedaan excess return selama pandemi COVID-19. Sedangkan hasil penelitian menunjukkan bahwa tidak terdapat perbedaan likuiditas saham sebelum dan sesudah pengumuman rights issue, baik sebelum maupun selama pandemi COVID-19. Begitupun hasil pengujian dividen terdapat perbedaan DPS sebelum dan sesudah pengumuman right issue sebelum COVID-19 yang ditunjukkan dengan perbedaan jumlah rata-rata DPS sebelum dan sesudah right issue, sementara DPS saat COVID-19 tidak terdapat perbedaan yang signifikan, membuktikan bahwa adanya pengaruh pandemi yang menyebabkan perlambatan ekonomi berdampak terhadap pasar modal, sehingga kegiatan penawaran terbatas yang dilakukan perusahaan dengan menerbitkan right issue menyebabkan jumlah lembar saham yang beredar meningkat namun laba yang diperoleh perusahaan tidak mengalami peningkatan. Hasil empiris menunjukkan bahwa pasar modal Indonesia mengikuti bentuk semi strong dari efisiensi pasar., The COVID-19 pandemic has the impact of fluctuations on stock price movements, and greatly affects economic conditions as well as investors' reactions to rights issue policies which will affect the interest in buying and selling shares. A study of the development of market activity in which investors react to information taking into account the dynamic nature of the market through bulls and bears before and during the COVID-19 pandemic. This study aims to identify the bullish and bearish periods on the Indonesia Stock Exchange for the 2017-2020 period, the influence of the influence of COVID-19 on the rights issue, to analyze the difference in average excess return and stock liquidity as measured by the bid-ask spread before and after the announcement of rights. the issue of the period before and during the COVID-19 pandemic, then analyze the effect of the right issue on dividends per share that will be received by shareholders before and during the COVID-19 pandemic, as well as whether the Indonesian capital market follows a semi-strong efficient market.
Keyword: Bullish, Bearish, Bid-Ask Spread, COVID-19, Excess Return, Semi Strong From

Judul: Overreaction Phenomenon on Sharia Stocks in Indonesia During COVID-19 Pandemic
Abstrak: Pandemi COVID-19 memberikan dampak yang meluas hingga sektor pasar modal. Penurunan harga saham terjadi pada saham syariah Indonesia di masa tersebut. Berbagai informasi selama pandemi membuat investor memberi reaksi yang berlebihan dan menyebabkan ketidakefisienan pasar. Penelitian ini bertujuan untuk mengidentifikasi fenomena overreaction pada saham syariah serta menganalisis faktor-faktor yang memengaruhinya. Pendekatan yang digunakan dalam penelitian ini ialah event study. Hasil uji beda menunjukkan bahwa fenomena overreaction terjadi pada portofolio saham winner saat pengumuman kasus COVID-19 pertama di Indonesia (Event 1), sedangkan pada peristiwa penerbitan program PEN (Event 3), kedatangan vaksin COVID-19 di Jakarta (Event 6), dan kenaikan kasus positif harian COVID-19 tertinggi per-Agustus 2021 (Event 10) fenomena overreaction terjadi pada portofolio saham winner-loser. Hasil cross sectional regression menunjukkan bahwa faktor-faktor yang signifikan memengaruhi fenomena overreaction yaitu abnormal return, kebocoran informasi, dan kepemilikan perusahaan yang terbukti secara signifikan dan berhubungan negatif terhadap nilai cumulative abnormal return (CAR) pada periode setelah peristiwa sebagai indikator dari fenomena overreaction., COVID-19 pandemic has a widespread impact on the capital market sector. The decline in stock prices occurred in Indonesian Islamic stocks at that time. Various information during the pandemic made investors overreact and led to market inefficiency. This study aims to identify the phenomenon of overreaction in Islamic stocks and analyze the factors that influence it. The approach used in this research is event study. The results show that overreaction occurred in winner stocks during the announcement of the first COVID-19 case in Indonesia (Event 1), while in the event of the issuance of the PEN program (Event 3), the arrival of the COVID-19 vaccine in Jakarta (Event 6), and the increase in The highest daily positive COVID-19 cases per August 2021 (Event 10) overreaction phenomenon occurred in winner-loser stocks. The results of cross sectional regression show that abnormal returns, leakage of information, and institutional ownership has a significant negative effect to cumulative abnormal return (CAR) in the period after the event as an indicator of the overreaction phenomenon.
Keyword: COVID-19, cross sectional regression, event, overreaction

Judul: Penggunaan Teorema Homeomorphy 2-Manifold dan Teorema Euler Poincare pada Torus 𝑇�� dan Simplicial Complex 𝐾��
Abstrak: Two dimensional topological spaces are said to be homeomorphic if they have the same topological invariant, where one of topological invariant used is an Euler characteristic. Homeomorphy 2-Manifold’s Theorem and Euler Poincare’s Theorem are used to distinguish two topological spaces. Homeomorphy 2-Manifold’s Theorem uses Euler characteristic to identify two dimensional topological spaces. Euler Poincare’s Theorem is an alternative way to find Euler characteristic with Betti number, which is topological invariant as well. The objective of this paper is to investigate the homeomorphism of torus 𝑇����� and simplicial complex 𝐾�����. Topological space torus and simplicial complex 𝐾����� have the same Euler characteristic, which is two. Based on Homeomorphy 2-Manifold’s Theorem topological space torus 𝑇����� and simplicial complex 𝐾����� is homeomorphic.
Keyword: simplicial, torus, Euler, homeomorphism, topology